Evaluation of Waning of SARS-CoV-2 Vaccine-Induced Immunity: A Systematic Review and Meta-analysis

Vaccine effectiveness dynamics against influenza and SARS-CoV-2 in community-tested patients in France 2023-2024

The epidemiology of respiratory viruses and vaccine effectiveness (VE) in the community are not well described. This study assessed VE against a positive test of influenza (VEf) and SARS-CoV-2 (VECov). Data from networks of community-based laboratories in France were collected during standard of care in the 2023-2024 epidemic season (n = 511,083 multiplex RT-PCR tests). Patients' demographics and symptoms were reported in addition to viral sequencing results. The test-negative design was used to estimate VEf and VECov by time since vaccination and calendar week. Adjusted VEf by age, sex, presence of symptoms, PCR technique, and week of testing, was 47.6% (95% CI: 44.3-50.7%). VEf was lower in patients ≥65 years (42.0%; 95% CI: 36.6-46.9%) than in 18-64 years (52.9%; 95% CI: 48.6-56.8%). The adjusted VEf against type A influenza, which represented 98% of typed viruses, was 51% (45%-56.6%) for patients vaccinated 15 days to 3 months before testing, and 35.5% (24.2%-45.3%) for those vaccinated 3-6 months before testing. For VECov, the adjusted estimate in patients vaccinated 15 days to 3 months prior to testing was 40.6% (7.2%-58.6%) at week 39, 24.8% (4.0%-38.8%) at week 45, and dropped systematically through the epidemic season as the JN.1 variant became dominant. This study showed moderate VEf and VECov against infection in the community and highlighted the impact of time since vaccination and age for both estimates, and the new variant emergence on VECov. These findings should be considered in future vaccination campaigns.

Protection and waning of vaccine-induced, natural and hybrid immunity to SARS-CoV-2 in Hong Kong

BACKGROUND

As the COVID-19 pandemic transitions into its fourth year, understanding the dynamics of immunity is critical for implementing effective public health measures. This study examines vaccine-induced, natural, and hybrid immunity to SARS-CoV-2 in Hong Kong, focusing on their protective effectiveness and waning characteristics against infection during the Omicron BA.1/2 dominant period.

RESEARCH DESIGN AND METHODS

We conducted a territory-wide retrospective cohort study using vaccination and infection records from the Hong Kong Department of Health. The analysis included over 6.5 million adults, applying the Andersen-Gill model to estimate protective effectiveness while addressing selection bias through inverse probability weighting.

RESULTS

Vaccine-induced immunity peaked one month after the first dose but waned rapidly, while boosters significantly prolonged protection. Infection-induced immunity showed higher initial effectiveness but declined faster than vaccine-induced immunity. Hybrid immunity provided the most durable protection. mRNA vaccines (Comirnaty) demonstrated greater effectiveness and slower waning compared to inactivated vaccines (CoronaVac).

CONCLUSIONS

Hybrid immunity represents the most effective strategy for sustained protection against SARS-CoV-2. Public health policies should emphasize booster campaigns and hybrid immunity pathways to enhance population-level immunity and guide future COVID-19 management in Hong Kong.

COVID-19 vaccine effectiveness among healthcare workers during the Omicron period in the country of Georgia, January - June 2022

INTRODUCTION

Understanding COVID-19 vaccine effectiveness (VE) in healthcare workers (HCWs) is critical to inform vaccination policies. We measured COVID-19 VE against laboratory-confirmed symptomatic infection in HCWs in the country of Georgia from January - June 2022, during a period of Omicron circulation.

METHODS

We conducted a cohort study of HCWs in six hospitals in Georgia. HCWs were enrolled in early 2021. Participants completed weekly symptom questionnaires. Symptomatic HCWs were tested by RT-PCR and/or rapid antigen test (RAT). Participants were also routinely tested, at varying frequencies during the study period, for SARS-CoV-2 by RT-PCR or RAT, regardless of symptoms. Serology was collected quarterly throughout the study and tested by electrochemiluminescence immunoassay for SARS-CoV-2 antibodies. We estimated absolute and relative VE of a first booster dose compared to a primary vaccine series as (1-hazard ratio)*100 using Cox proportional hazards models.

RESULTS

Among 1253 HCWs, 141 (11%) received a primary vaccine series (PVS) and a first booster, 855 (68%) received PVS only, and 248 (20%) were unvaccinated. Most boosters were BNT162b2 (Comirnaty original monovalent) vaccine (90%) and BBIBP-CorV vaccine (Sinopharm) (9%). Most PVS were BNT162b2 vaccine (68%) and BBIBP-CorV vaccine (24%). Absolute VE for a first booster was 40% (95% Confidence Interval (CI) -56-77) at 7-29 days following vaccination, -9% (95% CI -104-42) at 30-59 days following vaccination, and -46% (95% CI -156-17) at ≥ 60 days following vaccination. Relative VE of first booster dose compared to PVS was 58% (95% CI 1-82) at 7-29 days following vaccination, 21% (95% CI -33-54) at 30-59 days following vaccination, and -9% (95% CI -82-34) at ≥ 60 days following vaccination.

CONCLUSION

In Georgia, first booster dose VE against symptomatic SARS-CoV-2 infection among HCWs was moderately effective but waned very quickly during Omicron. Increased efforts to vaccinate priority groups in Georgia, such as healthcare workers, prior to periods of anticipated high COVID-19 incidence are essential.

Immunogenicity and safety of a monovalent Omicron XBB.1.5 SARS-CoV-2 recombinant spike protein vaccine in previously unvaccinated, SARS-CoV-2 seropositive participants: Primary day-28 analysis of a phase 2/3 open-label study

BACKGROUND

Most of the population has been infected with SARS-CoV-2 and, thus, is primed by natural exposure. As such, it was assessed whether a single dose of the monovalent XBB.1.5 vaccine, NVX-CoV2601, elicited a comparable immune response to XBB.1.5 in seropositive unvaccinated participants to that in previously vaccinated participants, thereby allowing the former to forego a two-dose primary series.

METHODS

In this phase 2/3, open-label, single-arm study (2019nCoV-313/NCT05975060 [group 2]), vaccine-naive participants ≥18 years with previous SARS-CoV-2 infection received one dose of NVX-CoV2601. This analysis compared the 28-day immunogenicity and safety of NVX-CoV2601 in vaccine-naive and previously vaccinated (≥3 prior mRNA-based vaccines, from 2019nCoV-313 group 1) participants. Noninferiority of neutralizing antibody (nAb) response in vaccine-naive versus vaccinated participants was the primary objective. The day-28 geometric mean titer (GMT) ratio (GMTR) and seroresponse rate (SRR; percentage of participants with a ≥4-fold rise in antibody response from baseline) were measured, and safety was assessed.

RESULTS

Of the participants enrolled from September 11 to November 15, 2023, per-protocol sets included 306/338 (90.5%) vaccine-naive and 309/332 (93.1%) vaccinated participants. At day 28, adjusted GMTs (95% CI) against XBB.1.5 in the vaccine-naive and vaccinated groups were 1491.5 (1277.5-1741.4) and 841.4 (723.9-978.0), respectively. The vaccine-naive-vaccinated nAb GMTR was 1.8 (95% CI 1.43-2.20) and SRRs were 74.3% and 64.3% for vaccine-naive and vaccinated participants, respectively (SRR difference: 10.0 [95% CI 2.6-17.4]). No new safety signals or events of special interest were reported.

CONCLUSIONS

A single dose of NVX-CoV2601 in vaccine-naive participants with a history of SARS-CoV-2 infection elicited a robust neutralizing antibody response that was noninferior to that observed in vaccinated participants. The vaccine was well-tolerated. These data support the use of NVX-CoV2601 as a single dose, regardless of prior vaccination history.

TRIAL REGISTRATION

NCT05975060.

An adjuvanted chimeric spike antigen boosts lung-resident memory T-cells and induces pan-sarbecovirus protective immunity

Next-generation vaccines are essential to address the evolving nature of SARS-CoV-2 and to protect against emerging pandemic threats from other coronaviruses. These vaccines should elicit broad protection, provide long-lasting immunity and ensure equitable access for all populations. In this study, we developed a panel of chimeric, full-length spike antigens incorporating mutations from previous, circulating and predicted SARS-CoV-2 variants. The lead candidate (CoVEXS5) was produced through a high-yield production process in stable CHO cells achieving >95% purity, demonstrated long-term stability and elicited broadly cross-reactive neutralising antibodies when delivered to mice in a squalene emulsion adjuvant (Sepivac SWE™). In both mice and hamsters, CoVEXS5 immunisation reduced clinical disease signs, lung inflammation and organ viral titres after SARS-CoV-2 infection, including following challenge with the highly immunoevasive Omicron XBB.1.5 subvariant. In mice previously primed with a licenced mRNA vaccine (Comirnaty XBB.1.5, termed mRNA-XBB), CoVEXS5 boosting significantly increased neutralising antibody (nAb) levels against viruses from three sarbecoviruses clades. Boosting with CoVEXS5 via systemic delivery elicited CD4+ lung-resident memory T cells, typically associated with mucosal immunisation strategies, which were not detected following mRNA-XBB boosting. Vaccination of hamsters with CoVEXS5 conferred significant protection against weight loss after SARS-CoV-1 challenge, compared to mRNA-XBB immunisation, that correlated with anti-SARS-CoV-1 nAbs in the sera of vaccinated animals. These findings highlight the potential of a chimeric spike antigen, formulated in an open-access adjuvant, as a next-generation vaccine candidate to enhance cross-protection against emerging sarbecoviruses in vaccinated populations globally.

Barriers to initial COVID-19 booster among US adults who completed a primary vaccine series in the CHASING COVID cohort, September 2021-October 2022

It is crucial to understand factors associated with COVID-19 booster uptake in the United States given the updated COVID-19 vaccine recommendations. Using data from a national prospective cohort (n = 4616) between September 2021 and October 2022, we examined socioeconomic, demographic, and behavioral factors of initial booster uptake among participants fully vaccinated with the primary COVID-19 vaccines series. Cox proportional hazards models were used to estimate the associations of each factor with time to initial booster uptake. Most participants (86.5%) reported receiving their initial booster. After adjusting for age, race/ethnicity, education, region, and employment, participants with greater risk for severe COVID-19 had similar booster uptake compared with those with lower risk (adjusted hazard ratio [aHR], 1.04; 95% CI, 0.95-1.14). Participants with greater barriers to healthcare (aHR, 0.89; 95% CI, 0.84-0.96), food insecurity (aHR, 0.82; 95% CI, 0.75-0.89), and housing instability (aHR, 0.81; 95% CI, 0.73-0.90) were less likely to report receiving initial booster compared with those without those barriers. Factors motivating the decision to vaccinate changed from safety-related concerns for the primary series to perceived need for the booster. It is key to address economic and health access barriers to achieve equitable COVID-19 vaccine uptake and continued protection against COVID-19.

Effectiveness over time of a primary series of the original monovalent COVID-19 vaccines in adults in the United States

With data from 2 US claims databases (Optum, CVS Health) supplemented with Immunization Information System COVID-19 vaccine records, we evaluated overall and time-specific vaccine effectiveness (VE) of an initial primary series for 3 monovalent COVID-19 vaccines-BNT162b2, mRNA-1273, and JNJ-7836735-in adults (18-64 years). Vaccinated individuals were matched to unvaccinated comparators, and we estimated VE against any medically diagnosed COVID-19 and hospital/emergency department (ED)-diagnosed COVID-19. Additionally, we estimated VE by era of predominant variants, in subgroups, and compared across vaccine brands. The cohorts consisted of 341,097 (Optum) and 1,151,775 (CVS Health) matched pairs for BNT162b2; 201,604 (Optum) and 651,545 (CVS Health) for mRNA-1273; and 49,285 (Optum) and 149,813 (CVS Health) for JNJ-7836735. The study period began 11 December 2020 (date of first COVID-19 vaccine availability in the US) and ended 15 January 2022 in Optum and 31 March 2022 in CVS Health. Summary VE estimates from meta-analysis against hospital/ED-diagnosed COVID-19 were: BNT162b2, 77% (95% CI, 76%-78%); mRNA-1273, 84% (95% CI, 83%-85%), JNJ-7836735 66% (95% CI, 63%-68%). VE estimates were higher for hospital/ED-diagnosed COVID-19 than for medically diagnosed COVID-19, and VE estimates were highest in adults receiving mRNA-1273 for both outcomes. VE was sustained for approximately 7 months for medically diagnosed and up to 9 months for hospital/ED-diagnosed COVID-19. VE differed by brand and variant era. Ongoing real-world surveillance of COVID-19 vaccines using robust data sources and methodology is needed as new variants and recommendations for updated vaccines have evolved.

Effectiveness of a single COVID-19 mRNA vaccine dose in individuals with prior SARS-CoV-2 infection: a systematic review

BACKGROUND

Based on high population immunity to SARS-CoV-2 from prior infection, vaccination, or both, in fall 2023, regulatory agencies globally authorized/approved a single mRNA XBB.1.5-adapted vaccine dose for individuals aged ≥5 years regardless of prior vaccination.

METHODS

We conducted a systematic review on vaccine effectiveness (VE) of a single COVID-19 mRNA dose in individuals with a history of prior infection compared to individuals who were (i) SARS-CoV-2 naïve, (ii) unvaccinated with prior infection, and (iii) vaccinated with >1 dose with or without prior infection. We searched MEDLINE and Embase for studies published January 2021-October 2023. Data were synthesized following Synthesis Without Meta-Analysis guidelines; bias was assessed using the Newcastle-Ottawa Scale. This study was registered with PROSPERO (CRD42023453257).

RESULTS

Eighteen studies were eligible. None of these studies reported bivalent or XBB.1.5-adapted VE, and none reported VE for immunocompromised populations or children aged <5 years. Among those with prior infection, a single mRNA dose increased protection by 8-71% against infection (during Omicron BA.1, BA.4/5, or XBB predominance), 39-67% against symptomatic infection (BA.1, BA.2, or BA.4/5), and 25-60% against hospitalization or hospitalization or death (BA.1). VE of one dose was comparable to two doses among those with prior infection, and higher than following two doses without prior infection.

CONCLUSIONS

A single dose of original mRNA COVID-19 vaccine provides similar protection to two doses for immunocompetent individuals aged ≥5 years in the current setting of high pre-existing immunity. This supports current recommendations for one dose to be given in advance of the respiratory season, regardless of history of infection or vaccination, with considerations for additional doses for certain populations including young children, older adults, and the immunocompromised.

Immunogenicity and safety of a monovalent omicron XBB.1.5 SARS-CoV-2 recombinant spike protein vaccine as a heterologous booster dose in US adults: interim analysis of a single-arm phase 2/3 study

BACKGROUND

Authorities globally recommended a monovalent omicron XBB.1.5-based COVID-19 vaccine for the 2023-24 season. The Novavax COVID-19 vaccine, NVX-CoV2601, contains XBB.1.5 recombinant spike protein, based on an authorised prototype vaccine (NVX-CoV2373) technology. We aimed to determine whether a single dose of NVX-CoV2601 versus NVX-CoV2373 (from a previous study [2019nCoV-311 part 2]) produced superior neutralising antibody (nAb) responses, and non-inferior seroresponse rates to XBB.1.5, after three or more previous mRNA-based COVID-19 vaccinations.

METHODS

In part 1 of this single-arm, phase 2/3 study (2019nCoV-313), participants aged 18 years or older who had been previously vaccinated with three or more doses of mRNA-1273 (Moderna) or BNT162b2 (Pfizer-BioNTech) were enrolled across 30 US centres (research groups and universities) located across 20 states. Participants received one intramuscular injection of NVX-CoV2601 (5 μg XBB.1.5 spike plus 50 μg Matrix-M adjuvant). Coprimary endpoints were superiority of baseline-adjusted nAb geometric mean XBB.1.5 titres (adjusted GMTs), with superiority declared when the lower bound of the 95% CI for the GMT ratio (GMTR) was greater than 1, and non-inferiority of seroresponse rates, with non-inferiority declared when the lower bound of the 95% CI for the seroresponse rate difference was greater than -10%, on day 28; comparisons were made for NVX-CoV2601 administered in this study versus NVX-CoV2373 administered in part 2 (group G) of the 2019nCoV-311 study. Coprimary endpoints were assessed in the per-protocol immunogenicity set (ie, all participants who received study vaccine, underwent 28 days of follow-up, had day 0 and day 28 samples available, and had no major protocol deviations). Safety was a secondary endpoint and included assessments of solicited treatment-emergent adverse events up to 7 days and unsolicited treatment-emergent adverse events up to 28 days after vaccination in the safety analysis set (ie, all participants who received study vaccine). Here we report the prespecified interim analysis of immunogenicity and safety up to day 28. This study is registered with ClinicalTrials.gov, NCT05975060, and is now complete.

FINDINGS

Between Sept 7 and Sept 8, 2023, 380 individuals were screened, of whom 332 were enrolled and received study vaccine. At the 28-day interim analysis database lock (Jan 17, 2023), the per-protocol analysis sets included 309 (93%) of 332 NVX-CoV2601 recipients and 227 (90%) of 252 NVX-CoV2373 recipients. Mean age of NVX-CoV2601 recipients was 52·1 years (SD 16·1); 192 (62%) of 309 were female and 117 (38%) were male. Mean age of NVX-CoV2373 recipients was 42·2 years (13·4); 128 (56%) of 227 were female and 99 (44%) were male. At day 28, the baseline-adjusted nAb GMT for NVX-CoV2601 was 905·9 (95% CI 807·1-1016·8) and for NVX-CoV2373 was 156·6 (137·0-179·0); the between-group adjusted GMTR was 5·8 (95% CI 4·9-6·9). In the per-protocol immunogenicity set, seroresponse rates were 64% (196 of 305) among recipients of NVX-CoV2601 and 7% (16 of 227) among recipients of NVX-CoV2373, with a seroresponse rate difference of 57% (95% CI 51-63). In the NVX-CoV2601 group, within 7 days, solicited local treatment-emergent adverse events were reported in 189 (57%) of 332 participants (including one [<1%] grade 3 or worse event; tenderness) and solicited systemic treatment-emergent adverse events were reported in 158 (48%) participants (including four [1%] participants with one or more grade 3 events; malaise [n=3], headache [n=2], fatigue [n=1], and muscle pain [n=1]). The most common solicited treatment-emergent adverse events were tenderness (171 [52%]) and pain (98 [30%]) at the injection site, fatigue (97 [29%]), and muscle pain (97 [29%]). Up to day 28, unsolicited adverse events considered related to study vaccination in the NVX-CoV2601 group occurred in five (2%) participants (one for each of asthma, axillary pain, diarrhoea, hypertension [which was medically attended], and presyncope). No serious adverse events due to study product, adverse events of special interest, or deaths due to study product occurred, and no study discontinuations due to treatment-emergent adverse events occurred.

INTERPRETATION

The coprimary endpoints were met, and NVX-CoV2601 was well tolerated. These interim data support NVX-CoV2601 use per guidance for XBB.1.5-directed COVID-19 vaccines and demonstrate the adaptability of this vaccine platform for updated SARS-CoV-2 spike proteins.

FUNDING

Novavax.

Causal Estimands for Analyses of Averted and Avertible Outcomes due to Infectious Disease Interventions

During the coronavirus disease (COVID-19) pandemic, researchers attempted to estimate the number of averted and avertible outcomes due to vaccination campaigns to quantify public health impact. However, the estimands used in these analyses have not been previously formalized. It is also unclear how these analyses relate to the broader framework of direct, indirect, total, and overall causal effects under interference. Here, using potential outcome notation, we adjust the direct and overall effects to accommodate analyses of averted and avertible outcomes. We use this framework to interrogate the commonly held assumption that vaccine-averted outcomes via direct impact among vaccinated individuals (or vaccine-avertible outcomes via direct impact among unvaccinated individuals) is a lower bound on vaccine-averted (or -avertible) outcomes overall. To do so, we describe a susceptible-infected-recovered-death model stratified by vaccination status. When vaccine efficacies wane, the lower bound fails for vaccine-avertible outcomes. When transmission or fatality parameters increase over time, the lower bound fails for both vaccine-averted and -avertible outcomes. Only in the simplest scenario where vaccine efficacies, transmission, and fatality parameters are constant over time, outcomes averted via direct impact among vaccinated individuals (or outcomes avertible via direct impact among unvaccinated individuals) is a lower bound on overall impact. In conclusion, the lower bound can fail under common violations to assumptions on time-invariant vaccine efficacy, pathogen properties, or behavioral parameters. In real data analyses, estimating what seems like a lower bound on overall impact through estimating direct impact may be inadvisable without examining the directions of indirect effects.

Optimal Timing of Vaccination: A Narrative Review of Integrating Strategies for COVID-19, Influenza, and Respiratory Syncytial Virus

Lower respiratory tract infections caused by SARS-CoV-2, influenza, and respiratory syncytial virus (RSV) cause a significant disease burden globally, despite the availability of effective vaccines. Certain populations, such as older adults (≥ 60 years) and individuals of all ages with particular comorbidities, are at increased risk for severe outcomes, including hospitalization and death. National administration schedules for available vaccines against respiratory viruses are not unified, and not all current guidelines are clear and directive, concerning the optimal timing of vaccination. Herein, we formulate an evidence-based position regarding the optimal timing of COVID-19, influenza, and RSV vaccination for older adults and individuals with chronic comorbidities, based on a synthesis of the literature and current guidelines. Vaccination impact and timing were found to be influenced by vaccinee risk factors, including age and comorbidities, and waning vaccine effectiveness and seasonal pathogen burden. Because COVID-19, influenza, and RSV display unique seasonal patterns within and between regions, local epidemiological surveillance of each virus is crucial for determining optimal vaccination timing and guidelines. To maximize the benefits of these respiratory virus vaccines, the timing of peak vaccine effectiveness and period of greatest risk for severe outcomes should be aligned. Thus, COVID-19, influenza, and other recommended vaccines given ahead of the start of the respiratory virus season (or other regionally appropriate time) and co-administered at a single, routine visit represent the optimal approach to protecting at-risk populations. More data will be required to establish the clinical benefit of additional RSV vaccine doses and whether these may be integrated within a seasonal schedule. Coordinated policy decisions that align with strain selection for new and annually reformulated vaccines would enable the timely raising of public health awareness, ultimately leading to enhanced vaccine uptake. Implementation strategies will require engagement of healthcare providers and strong, evidence-based public health recommendations for integrated vaccine schedules.

IPNA clinical practice recommendations on care of pediatric patients with pre-existing kidney disease during seasonal outbreak of COVID-19

The coronavirus disease 2019 (COVID-19) pandemic, instigated by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has profoundly impacted healthcare infrastructures around the globe. While children are usually asymptomatic or have mild symptoms, children with pre-existing kidney conditions require specialized attention. This pivotal report, championed by the International Pediatric Nephrology Association (IPNA), delivers precise and actionable recommendations tailored for pediatric patients with kidney ailments in this pandemic landscape. Central to our findings are rigorous infection control protocols. These are particularly stringent in high-risk zones, emphasizing telehealth's indispensable role, the significance of curtailing in-person consultations, and the imperative of following rigorous guidelines in regions with heightened COVID-19 prevalence. Additionally, the report delves into vaccination approaches for children with kidney issues, highlighting that the choice of vaccine is often governed by regional accessibility and policy frameworks, rather than a universal preference. A notable observation is the potential correlation between COVID-19 vaccines and specific kidney disorders. However, establishing a direct causal link remains elusive. In summary, our research accentuates the critical need for specialized pediatric kidney care during global health crises and reaffirms the continuous research imperative, especially regarding vaccination ramifications.

An agent-based model to assess the impact of shared staff and occupancy rate on infectious disease burden in nursing homes

Infectious diseases can propagate between nursing homes through asymptomatic staff members who are employed at multiple facilities. However, the transmission dynamics of infections, both within individual nursing homes and across facilities, has been less investigated. To fill this gap, we developed an agent-based model of two nursing homes extendible to a network of n nursing homes connected with different percentages of shared staff. Focusing on the outbreaks of COVID-19 in U.S. nursing homes, we calibrated the model according to the COVID-19 prevalence data and estimated levels of shared staff for each State. The model simulations indicate that reducing the percentage of shared staff below 5% plays a significant role in controlling the spread of infection from one nursing home to another through personal protective equipment usage, rapid testing, and vaccination. As the percentage of shared staff increases to more than 30%, these measures become less effective, and the mean prevalence of infection reaches a steady state in both nursing homes. The hazard ratios for infection and mortality indicate that nursing homes with higher occupancy rates are more significantly affected by increased staff-sharing percentages. In conclusion, the burden of infection significantly increases with greater staff sharing between nursing homes, particularly in high-occupancy facilities, where transmission dynamics are amplified due to greater resident density and staff interactions.

Macrophages direct location-dependent recall of B cell memory to vaccination

Vaccines generate long-lived plasma cells and memory B cells (Bmems) that may re-enter secondary germinal centers (GCs) to further mutate their B cell receptor upon boosting and re-exposure to antigen. We show in mouse models that lymph nodes draining the site of primary vaccination harbor a subset of Bmems that reside in the subcapsular niche, generate larger recall responses, and are more likely to re-enter GCs compared with circulating Bmems in non-draining lymph nodes. This location-dependent recall of Bmems into the GC in the draining lymph node was dependent on CD169+ subcapsular sinus macrophages (SSMs) in the subcapsular niche. In human participants, boosting of the BNT162b2 vaccine in the same arm generated more rapid secretion of broadly neutralizing antibodies, GC participation, and clonal expansion of SARS-CoV-2-specific B cells than boosting of the opposite arm. These data reveal an unappreciated role for primed draining lymph node SSMs in Bmem cell fate determination.

COVID-19 Vaccination Timing, Relative to Acute COVID-19, and Subsequent Risk of Long COVID

Objectives

Long COVID is a debilitating condition that impacts millions of Americans, but patients and clinicians have little information on how to prevent this disorder. Vaccination is a vital tool in preventing acute COVID-19 and may confer additional protection against Long COVID. There is limited evidence regarding the optimal timing of COVID-19 vaccination (i.e., vaccination schedule) to minimize the risk of Long COVID.

Methods

We applied Longitudinal Targeted Maximum Likelihood Estimation to electronic health record (EHR) data from a retrospective cohort of patients vaccinated against COVID-19 between December 2021 and September 2022. We evaluated the association between binary COVID-19 vaccination status (two or more doses vs. zero doses) and 12-month Long COVID risk among patients diagnosed with acute COVID-19 between December 2021 and September 2022. In addition, we compared the 12-month cumulative risk of Long COVID (ICD-10 code U09.9) among patients diagnosed with acute COVID-19 one to three months after vaccination, three to five months after vaccination, or five to seven months after vaccination while adjusting for relevant high-dimensional baseline and time-dependent covariates.

Results

We analyzed EHR data from a retrospective cohort of 1,558,018 patients. In our binary cohort (n = 519,980), we found that vaccinated patients had a lower risk of Long COVID than unvaccinated patients (adjusted marginal risk ratio 0.84 (0.81, 0.88)). In our longitudinal cohort (n = 1,085,291), we did not find a significant difference in Long COVID risk comparing patients who were diagnosed with acute COVID-19 one to three months after vaccination versus patients who were diagnosed with COVID-19 three to five months (adjusted marginal risk ratio 0.93 (95% CI 0.62, 1.41) or 5 to 7 months (adjusted marginal risk ratio 1.06 (95% CI 0.72, 1.56)) after vaccination.

Conclusions

We found that COVID-19 vaccination before SARS-CoV-2 infection was protective against Long COVID, and we did not find that this protection significantly waned within 7 months after vaccination. These findings suggest that COVID-19 vaccination protects against Long COVID.

Long-lasting antibody B-cell responses to SARS-CoV-2 three years after the onset of the pandemic

Immune memory is essential for the effectiveness of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination. In the current context of the pandemic, with a diminished vaccine efficacy against emerging variants, it remains crucial to perform long-term studies to evaluate the durability and quality of immune responses. Here, we examined the antibody and memory B-cell responses in a cohort of 113 healthcare workers with distinct exposure histories over a 3-year period. Previously infected and naive participants developed comparable humoral responses by 17 months after receiving a full three-dose mRNA vaccination. In addition, both maintained a substantial SARS-CoV-2-reactive memory B-cell pool, associated with a lower incidence of breakthrough infections in naive participants. Of note, previously infected participants developed an expanded SARS-CoV-2-reactive CD27-CD21- atypical B-cell population that remained stable throughout the follow-up period. Thus, previous SARS-CoV-2 infection differentially imprints the memory B-cell compartment without compromising the development of long-lasting humoral responses.

Impact of pre-Omicron COVID-19 vaccine boosters on the risk of Omicron variant infections: A systematic review and meta-regression

BACKGROUND

An argument against COVID-19 vaccine boosters is that immune imprinting may impair immune responses to new SARS-CoV-2 variants, as some epidemiological studies found a paradoxical increase in Omicron variant infections correlated with the number of prior pre-Omicron vaccine doses. However, substantial variability between studies has left the true impact of boosters uncertain, warranting further investigation.

METHODS

We systematically reviewed available data and applied meta-regression to identify sources of heterogeneity among studies that examined the impact of pre-Omicron COVID-19 vaccine boosters-compared with primary vaccination series without boosters-on the risk of Omicron variant infections and severe diseases.

RESULTS

We screened 1703 articles and included 35 eligible studies. Heterogeneities in the impact of pre-Omicron boosters on the risk of Omicron infections and severe diseases are attributable to differences in time after boosters, age, and vaccine products (meta-regression R2: 70.4 % and 67.7 %, respectively). During the first month post-vaccination, pre-Omicron mRNA boosters decrease-rather than increase-the risk of Omicron infections and severe diseases by 58 % (95 % CI: 54 %-62 %) and 80 % (95 % CI: 68 %-87 %). This effectiveness declines to 9 % (95 % CI: 7 %-23 %) and 55 % (95 % CI: 49 %-60 %) by the sixth and fifth month, respectively. The certainty for evidence is moderate for protection against infections and high for protection against severe diseases.

CONCLUSION

Our findings refute the immune imprinting hypothesis that COVID-19 boosters impair immunity against new SARS-CoV-2 variants and support current recommendations to stay protected through updated booster vaccination once or twice a year.

Tracking vaccine effectiveness in an evolving pandemic, countering misleading hot takes and epidemiologic fallacies

With the emergence of Omicron during the pandemic and the establishment of antibody waning over time, vaccine effectiveness, especially against infection, declined sharply from the original levels seen after the initial rollout. However, studies have demonstrated that they still provided substantial protection vs severe/fatal disease even with Omicron and after waning. Social media has been rife with reports claiming vaccines provided no benefit and some even claiming they made things worse, often driven by simple presentations of raw observational data using erroneous arguments involving epidemiologic fallacies including the base rate fallacy, Simpson's paradox, and the ecological fallacy and ignoring the extensive bias especially from confounding that is an inherent feature of these data. Similar fallacious arguments have been made by some in promoting vaccination policies, as well. Generally, vaccine effectiveness cannot be accurately estimated from raw population summaries but instead require rigorous, careful studies using epidemiologic designs and statistical analysis tools attempting to adjust for key confounders and sources of bias. This article summarizes what aggregated evidence across studies reveals about effectiveness of the mRNA vaccines as the pandemic has evolved, chronologically summarized with emerging variants and highlighting some of the fallacies and flawed arguments feeding social media-based claims that have obscured society's collective understanding.

[Cost effectiveness of vaccinations: on the complexity of health economic analyses of influenza, SARS-CoV-2 and RSV vaccination]

The question of the cost effectiveness of medical interventions is one of the central issues in health economics. This narrative review examines the cost effectiveness of vaccination against influenza, SARS-CoV‑2 and respiratory syncytial virus (RSV) considering current health economic analyses. The annual influenza vaccination and the booster vaccination against SARS-CoV‑2 in 2023 and 2024 are proving to be cost effective and in some cases even cost saving, especially in high-risk groups. The cost effectiveness of the RSV vaccination, which was approved in 2023, is less clear. It strongly depends on the age group and the willingness to pay for a quality-adjusted life year (QALY) gained. The analysis shows that the evaluation of vaccinations requires a considerable amount of data. In addition to direct protective effects, model calculations on vaccinations must also consider indirect effects, such as the reduction of transmission in the population with higher vaccination rates. Sensitivity analyses make it clear that factors such as vaccine costs, effectiveness and disease incidence can have a decisive influence on cost effectiveness. One of the biggest challenges in health economic analyses is the fragmentation of health data in many countries, which makes comprehensive and precise assessments difficult. Initiatives such as the European Health Data Space could help and support evidence-based decision making in health policy. Overall, the cost effectiveness of vaccinations remains dependent on numerous factors, with SARS-CoV‑2 and influenza vaccinations receiving a positive assessment in the scenarios analysed.

Immunogenicity of adjuvanted recombinant SARS-CoV-2 spike protein vaccine after earlier mRNA vaccine doses

BACKGROUND

To support heterologous vaccine regimens, periodic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) revaccination requires immunogenicity and safety data for adjuvanted protein-based vaccines following prior mRNA doses.

OBJECTIVE

We sought to assess noninferiority of neutralizing antibody (nAb) titers following a second dose versus a first dose (in a prior study) of an SARS-CoV-2 protein-based vaccine (NVX-CoV2373) administered following a primary series (2 or 3 doses) of an mRNA vaccine.

METHODS

This phase 3, open-label study (2019nCoV-312/NCT05875701) enrolled participants who had received 1 dose of the ancestral SARS-CoV-2 protein-based vaccine in an earlier study (2019nCoV-307/NCT05463068) after a primary series (2 or 3 doses) of a commercial mRNA vaccine. In the current study, participants received an additional dose of protein vaccine (ancestral [n = 104] or Omicron BA.5 [n = 40]) at least 180 days after their previous study dose.

RESULTS

The study enrolled 144 participants. The ratio of anti-Wuhan nAbs (geometric mean titer) at day 28 after this study dose (ancestral 393.2 IU/mL [95% CI 318.0-468.2]) versus previous study dose (396.6 IU/mL [95% CI 328.7-478.6]) was 1.0 (0.8-1.2), meeting noninferiority. The seroresponse rate difference between doses was 7.4% (95% CI -1.2% to 16.5%), also meeting noninferiority. Omicron BA.5 nAb titers suggest cross-protection against emerging variants. The anti-Wuhan nAb ratio at day 28 between Omicron BA.5 vaccine dose in this study (835.0 [597.1-1167.6]) versus the ancestral vaccine in the previous study (436.0 [305.6-622.2]) was 1.9 (1.5-2.5), exceeding superiority criterion. Local and systemic reactions were similar between doses and strains in both studies.

CONCLUSION

A heterologous regimen of 2 adjuvanted, recombinant spike protein vaccine doses following multiple mRNA vaccine doses produced robust immune responses, exhibiting cross-reactivity to some newer variants.

Age- and vaccination status-dependent isolation guidelines based on simulation of SARS-CoV-2 Delta cases in Singapore

BACKGROUND

In the absence of effective pharmaceutical interventions early in an infectious disease outbreak, non-pharmaceutical measures, especially isolating infected individuals, critically limit its impact. The ongoing COVID-19 pandemic has sparked debates on optimal isolation guidelines. This study proposes a variable isolation period approach (variable-period approach), tailoring isolation durations for distinct population groups with varied viral load dynamics.

METHODS

To compare our variable-period approach with a fixed-period strategy, we developed a simulation model generating synthetic longitudinal SARS-CoV-2 viral load data. The data was generated from the viral dynamics model parameterized using SARS-CoV-2 Delta patient data in Singapore, accounting for age and vaccination status.

RESULTS

Findings show that age and vaccination status significantly influence viral dynamics, with younger age and vaccination linked to shorter viral shedding durations. The variable-period framework suggests longer isolation lengths for older and unvaccinated individuals. By setting the leaking risk (risk of remaining infectious at the end of isolation) below 10%, the optimal fixed-period isolation is 14 days, with an average excess isolation burden of 7.4 unnecessary days. In contrast, the variable-period guideline reduces the excess isolation burden to 6.0 days, with the optimal isolation periods ranging from 9 to 16 days, depending on the population group. We confirmed similar results when we used the effective reproduction number as an alternative to the leaking risk.

CONCLUSIONS

In this case, study using the SARS-CoV-2 Delta variant, our analysis demonstrates that unnecessary time spent in isolation can be reduced by adopting variable-period guidelines based on patient characteristics.

Effectiveness of COVID-19 vaccines against laboratory-confirmed SARS-CoV-2 infection amongst health workers, Windhoek, Namibia

INTRODUCTION

As of 24 October 2021, 128,868 laboratory-confirmed COVID-19 cases and 3550 deaths were reported from Namibia. The national COVID-19 vaccination campaign that started in March 2021 included health workers (HWs) as a priority group. The vaccines most administered were Sinopharm, AstraZeneca, Pfizer-BioNtech, and Janssen. We aimed to measure the effectiveness of COVID-19 vaccines (VE) amongst HWs against laboratory-confirmed SARS-CoV-2 infection in Namibia.

METHODS

We conducted a test negative design (TND) amongst HWs from the two main hospitals treating COVID-19 patients. HWs were defined as all hospital staff over 18 years in direct or indirect contact with patients, eligible for COVID-19 vaccination. We interviewed actively recruited HWs with standardized questionnaires in-person from 25/10/2021 to 25/4/2022. The participants had to state their vaccination status, which was verified through vaccination card, vaccine registry and/or District Health Information System 2. RT-PCR testing of respiratory specimens and serological testing (Wantai and Platelia-ELISA) were conducted. We measured VE by comparing the vaccination status between RT-PCR positive and negative HWs using a multivariable logistic regression model, which was adjusted for confounders. We calculated VE = (1-odds ratio of vaccination)*100 %.

RESULTS

We included 1201 HWs of which 322 (26.8 %) participants were fully vaccinated with a primary series against COVID-19, 62 (5.2 %) were partially vaccinated and 735 (61.2 %) were not vaccinated. In total, 1119 (93 %) participants had antibodies against SARS-CoV-2 including 637 (90 %) of the unvaccinated participants. Fifty-eight (4.8 %) participants tested RT-PCR positive for SARS-CoV-2. The Omicron variant was detected in all 13 sequenced genomes (11 BA.1.18, 2 BA.1). The estimated overall VE for full vaccination was 61.8 % (95 %-confidence interval, 9.3-83.9 %).

CONCLUSIONS

The VE results suggest that COVID-19 vaccines used in Namibia provided good protection from infections with the Omicron variant even if many participants had a SARS-CoV-2 infection before the study. Therefore, COVID-19 vaccines should be administered to risk groups such as HWs independent from previous infections.

A phase I/II study of CpG/alum-adjuvanted mammalian-derived quadruple antigen carrying virus-like particle COVID-19 vaccine

BACKGROUND

Waning Spike-elicited immunity and emerging COVID-19 variants underscore the need for vaccines leveraging multiple SARS-CoV-2 antigens, rapidly adaptable to evolving strains. Herein, we evaluated the safety and immunogenicity of a CpG ODN-adjuvanted, alum-adsorbed, virus-like particle (VLP) vaccine displaying the hexaproline stabilized Spike (S) protein and the Nucleocapsid, Membrane, and Envelope proteins of SARS-CoV-2.

METHODS

In phase 1 randomized, double-blind, placebo-controlled, dose-escalation trial, participants (N = 38, aged 18-59) received two subcutaneous injections of either 10 μg or 40 μg of VLP or placebo, 21 days apart. The primary and secondary objectives of the study was to evaluate the safety, reactogenicity and immunogenicity, respectively. In the double blind, multi-center phase-2 study, participants (N = 349, aged 18-55) were randomized into three cohorts receiving two doses of 40 μg VLPs displaying Wuhan-Spike, Alpha-Spike, or a combination. The primary and secondary objectives were humoral, and cell mediated immunogenicity (CMI) and safety, respectively. Antibody responses were analyzed using ELISA while ELIspot and CBA assays were used to assess the CMI.

RESULTS

The VLP vaccine demonstrated a good safety profile, with 255 non-serious adverse events in phase 1 and 308 in phase 2. Five serious AEs were reported in phase 2, all of which were resolved completely. The VLP vaccine, in phase 2, was well-tolerated, elicited moderate but sustained anti-S and anti-N antibody titers for 180 days and induced T-helper-1 biased cellular responses in participants.

CONCLUSIONS

The VLP platform is rapidly adaptable to accommodate stabilized Spike proteins from emerging variants and inclusion of other structural SARS-CoV-2 proteins could broaden the breadth of T cell-mediated immunity.

CLINICALTRIALS

gov; NCT04818281 and NCT04962893.

COVALENCE STUDY: Immunogenicity and Reactogenicity of a COVID-19 mRNA Vaccine in an Open-Label Cohort of Long-Survivor Patients with Metastatic Lung Cancer

Background: As COVID-19 has become an epidemic, we conducted an open-label study aimed to identify immunogenicity and reactogenicity of boosters of the BNT162b2 vaccine in a real-world cohort of long-survivor metastatic lung cancer patients (LS-mLC pts). Methods and Analysis: According to the timing of the booster dose (BD) and SARS-CoV-2 infection (Cov-I) during anticancer treatment (ACT), between October 2021 and February 2022, we prospectively enrolled 166 cancer patients into five parallel cohorts. The primary endpoints were seroprevalence of IgG Anti-spike-RBD (anti-S IgG) at two pre-defined timepoints (T1: +30-90 days after BD; T2: +6 months +/- 4 weeks after BD). As an exploratory endpoint, we compared the median pre-vaccination value of four cytokines (IL-6, IL-2R, TNF-α, IL-10) with post-BD values in immunotherapy-treated pts (IO-pts). Results: The anti-S IgG seropositivity rate was 100% at T1 and 98.8% at T2. After 6 months, hybrid immunisation was associated with a higher median anti-S IgG titre compared to vaccine-alone-induced seroconversion (p < 0.0001). In uninfected pts, the median anti-S IgG titre was significantly lower in IO-pts compared to non-IO-pts (p = 0.02); no difference was found when comparing myelosuppressive or not ACT. Among the 68 IO-pts, 5 pts (7.3%) showed a significant increase (≥1.5 fold) of at least two cytokines in post-BD samples, without reporting ir-AEs. Conclusions: Boosters of the COVID-19 mRNA vaccine were effective and safe. In IO-pts without recent Cov-I, additional BDs should be considered to prolong serological immunity.

Impact of vaccination on Omicron's escape variants: Insights from fine-scale modelling of waning immunity in Hong Kong

COVID-19 vaccine-induced protection declines over time. This waning of immunity has been described in modelling as a lower level of protection. This study incorporated fine-scale vaccine waning into modelling to predict the next surge of the Omicron variant of the SARS-CoV-2 virus. In Hong Kong, the Omicron subvariant BA.2 caused a significant epidemic wave between February and April 2022, which triggered high vaccination rates. About half a year later, a second outbreak, dominated by a combination of BA.2, BA.4 and BA.5 subvariants, began to spread. We developed mathematical equations to formulate continuous changes in vaccine boosting and waning based on empirical serological data. These equations were incorporated into a multi-strain discrete-time Susceptible-Exposed-Infectious-Removed model. The daily number of reported cases during the first Omicron outbreak, with daily vaccination rates, the population mobility index and daily average temperature, were used to train the model. The model successfully predicted the size and timing of the second surge and the variant replacement by BA.4/5. It estimated 655,893 cumulative reported cases from June 1, 2022 to 31 October 2022, which was only 2.69% fewer than the observed cumulative number of 674,008. The model projected that increased vaccine protection (by larger vaccine coverage or no vaccine waning) would reduce the size of the second surge of BA.2 infections substantially but would allow more subsequent BA.4/5 infections. Increased vaccine coverage or greater vaccine protection can reduce the infection rate during certain periods when the immune-escape variants co-circulate; however, new immune-escape variants spread more by out-competing the previous strain.

An LNP-mRNA vaccine modulates innate cell trafficking and promotes polyfunctional Th1 CD4+ T cell responses to enhance BCG-induced protective immunity against Mycobacterium tuberculosis

BACKGROUND

Mycobacterium tuberculosis remains the largest infectious cause of mortality worldwide, even with over a century of widespread administration of the only licenced tuberculosis (TB) vaccine, Bacillus Calmette-Guérin (BCG). mRNA technology remains an underexplored approach for combating chronic bacterial infections such as TB.

METHODS

We have developed a lipid nanoparticle (LNP)-mRNA vaccine, termed mRNACV2, encoding for the M. tuberculosis CysVac2 fusion protein, which we have previously formulated as an adjuvanted subunit vaccine. This LNP-mRNA vaccine was administered intramuscularly to female C57BL/6 mice as a standalone vaccine or as booster to BCG to assess immunogenicity and efficacy of the construct.

FINDINGS

Vaccination with mRNACV2 induced high frequencies of polyfunctional, antigen-specific Th1 CD4+ T cells in the blood and lungs, which was associated with the rapid recruitment of both innate and adaptive immune cells to lymph nodes draining the site of immunisation. mRNACV2 vaccination also provided significant pulmonary protection in M. tuberculosis-infected mice, reducing bacterial load and inflammatory infiltration in the lungs. Importantly, mRNACV2 enhanced immune responses and long-term protection when used to boost BCG-primed mice.

INTERPRETATION

These findings of a protective LNP-mRNA vaccine for TB highlight the potential of the LNP-mRNA platform for TB control and support further research to facilitate translation to humans.

FUNDING

This work was supported by the NHMRC Centre of Research Excellence in Tuberculosis Control to JAT and WJB (APP1153493), and MRFF mRNA Clinical Trial Enabling Infrastructure grant to CWP and HAW (MRFCTI000006).

Planning and adjusting the COVID-19 booster vaccination campaign to reduce disease burden

As public health policies shifted in 2023 from emergency response to long-term COVID-19 disease management, immunization programs started to face the challenge of formulating routine booster campaigns in a still highly uncertain seasonal behavior of the COVID-19 epidemic. Mathematical models assessing past booster campaigns and integrating knowledge on waning of immunity can help better inform current and future vaccination programs. Focusing on the first booster campaign in the 2021/2022 winter in France, we used a multi-strain age-stratified transmission model to assess the effectiveness of the observed booster vaccination in controlling the succession of Delta, Omicron BA.1 and BA.2 waves. We explored counterfactual scenarios altering the eligibility criteria and inter-dose delay. Our study showed that the success of the immunization program in curtailing the Omicron BA.1 and BA.2 waves was largely dependent on the inclusion of adults among the eligible groups, and was highly sensitive to the inter-dose delay, which was changed over time. Shortening or prolonging this delay, even by only one month, would have required substantial social distancing interventions to curtail the hospitalization peak. Also, the time window for adjusting the delay was very short. Our findings highlight the importance of readiness and adaptation in the formulation of routine booster campaign in the current level of epidemiological uncertainty.

Clinical profile analysis of SARS-CoV-2 community infections during periods with omicron BA.2, BA.4/5, and XBB dominance in Hong Kong: a prospective cohort study

BACKGROUND

Existing studies on SARS-CoV-2 infection have mainly focused on severe clinical outcomes; understanding of the clinical severity profile of general community infections is poor. We aimed to assess and compare the clinical profiles of infections with SARS-CoV-2 omicron (B.1.1.529) subvariants in a representative community cohort in Hong Kong during periods of BA.2, BA.4/5, and XBB dominance.

METHODS

In this prospective cohort study in Hong Kong, a representative community cohort of individuals aged at least 5 years were recruited by random-digit dialling and underwent weekly rapid antigen testing for SARS-CoV-2, irrespective of symptoms, during three periods from March 1, 2022, to Oct 31, 2023, in which the BA.2, BA.4/5, or XBB subvariants were dominant. We analysed the likelihood of symptoms, as well as the patterns, severity, and duration of symptoms and their associations with participant demographics and vaccination and infection histories.

FINDINGS

1126 (11·0%) of 10 279 participants in the BA.2 period, 830 (6·6%) of 12 588 in the BA.4/5 period, and 633 (11·1%) of 5690 during the XBB period tested positive for SARS-CoV-2 infection on rapid antigen tests. Community infections were generally mild, with asymptomatic infections comprising 22·0-25·0% of infections. No hospitalisations or deaths occurred as a direct result of SARS-CoV-2 infection during the study period. Compared with children aged 5-17 years, a higher likelihood of being symptomatic on infection was found for adults aged 18-59 years during the period of BA.2 dominance and adults aged 60 years or older during XBB dominance. Most (>90·0%) participants with symptomatic infections reported respiratory and systemic symptoms. Up-to-date vaccination with a regimen containing the BNT162b2 vaccine, compared with those without an up-to-date vaccine, was associated with a reduced likelihood of symptoms on infection during the period of BA.2 dominance and of severe symptoms causing substantial disturbance to daily life (grade 3 symptoms) during periods of BA.2 and BA.4/5 dominance, whereas no association was observed during the period of XBB dominance. Previous SARS-CoV-2 infection was associated with a reduced likelihood of symptoms on infection during BA.4/5 and XBB dominance and of severe symptoms during XBB dominance. Reports of severe symptoms increased over the three periods, from 236 (27·7%) of 852 symptomatic participants during BA.2 dominance to 176 (37·1%) of 475 during XBB dominance. The duration of symptoms was longest in the BA.2 period (median 10·0 days [95% CI 9·0-10·0]) and similar in the other two periods (8·0 [8·0-9·0] during BA.4/5 dominance and 8·0 [8·0-9·0] during XBB dominance). A symptom duration of 60 days or longer was reported only during the period of BA.2 dominance, in six (0·7%) of 824 infections.

INTERPRETATION

SARS-CoV-2 infections were generally mild, but not increasingly so, along the evolution of omicron subvariants in this highly vaccinated population. About a third of participants with symptomatic infections reported that the symptoms severely affected daily life even if they were not admitted to hospital, resulting in morbidity, absence from work or school due to illness, productivity loss, and increased medicoeconomic burden. A gradual reduction in the association of vaccines and increase in the association of previous infection with the symptom profile, possibly reflecting the effects of immune escape and waning, were observed over the study period.

FUNDING

Henry Fok Foundation and Hong Kong Health Bureau.

Immunogenicity of a booster dose of a bivalent (Asp614Gly and omicron BA.4/5 variant) self-amplifying mRNA SARS-CoV-2 booster vaccine versus the BNT162b2 omicron BA.4/5 mRNA vaccine: a randomised phase 3 trial

BACKGROUND

We previously showed that ARCT-154, a self-amplifying mRNA COVID-19 vaccine, had improved immunogenicity and antibody persistence compared with conventional mRNA or adenovirus vector vaccines. In this study, we compared ARCT-2301, a bivalent self-amplifying mRNA vaccine (Asp614Gly and omicron BA.4/5 variant), with the bivalent Comirnaty omicron BA.4-5 vaccine, to determine whether this improved response persisted in bivalent formulations against different SARS-CoV-2 variants.

METHODS

This randomised, multicentre, phase 3, observer-masked, active-controlled comparative study was done at nine hospitals in Japan. Eligible participants were healthy Japanese adults, aged at least 18 years, who had previously received a full immunisation series of three to five doses of mRNA COVID-19 vaccines (Comirnaty or Spikevax [Moderna]), with the last dose received at least 3 months before screening for this trial. Participants were randomly assigned (1:1) to either ARCT-2301 or Comirnaty BA.4-5 mRNA vaccine using interactive computer-generated randomisation with a block size of four. Randomisation was stratified by gender (men vs women), age group (<65 years vs ≥65 years), type of vaccine used for last vaccination (bivalent omicron BA.1 vs bivalent omicron BA.4/5), and time since last COVID-19 vaccination (<5 months vs ≥5 months). ARCT-2301 was supplied in vials containing 100 μg lyophilised mRNA, 50 μg mRNA each coding for the full-length spike proteins of the ancestral Asp614Gly SARS-CoV-2 strain and omicron BA.4/5 variant. Immediately before use, each vial was reconstituted with 10 mL saline. The comparator original omicron BA.4/5 mRNA vaccine (Comirnaty BA.4-5) was supplied in ready-to-use vials containing a single dose of 30 μg mRNA in 0·3 mL volume. Both vaccines were administered by intramuscular injection in the deltoid of the non-dominant arm. The primary outcome of the study was to show non-inferiority of immunogenicity of ARCT-2301 versus Comirnaty BA.4-5 at day 29 as neutralising antibody geometric mean titres (GMT) and seroresponse rates against omicron BA.4/5. Primary analyses were done in a per-protocol manner. The trial is registered with the Japan Registry for Clinical Trials, jRCT2031230340.

FINDINGS

Between Sept 29 and Nov 18, 2023, we enrolled 930 participants (451 men and 479 women) to receive a booster dose of ARCT-2301 (n=465) or Comirnaty BA.4-5 (n=465). The primary immunogenicity outcome to show that the antibody response at day 29 against omicron BA.4/5 elicited by ARCT-2301 was non-inferior to that elicited with Comirnaty BA.4-5 was achieved, both by GMT ratio (1·49, 95% CI 1·26-1·76) and difference in seroresponse rate (7·2%, 95% CI 0·6-13·7). Furthermore, the differences in antibody response between the groups showed superiority for ARCT-2301 against Wuhan-Hu-1 using both criteria, with a GMT ratio of 1·45 (95% CI 1·28-1·63) and a difference in seroresponse rate of 12·5% (95% CI 5·9-19·0), and omicron XBB.1.5, with a GMT ratio of 1·63 (95% CI 1·36-1·94) and a seroresponse rate difference of 16·7% (95% CI 10·1-23·2). Both vaccines were well-tolerated with mainly mild, transient solicited adverse events and no causally related severe or serious adverse events.

INTERPRETATION

Boosting mRNA-immunised adults with ARCT-2301 induced superior immunogenicity compared with Comirnaty BA.4-5 against both Wuhan-Hu-1 and omicron BA.4/5 variant COVID-19, and elicited a higher response against omicron XBB.1.5. Both vaccines had similar tolerability profiles. Self-amplifying mRNA vaccines could provide a substantial contribution to pandemic preparedness and response, inducing robust immune responses with a lower dose of mRNA to allow wider and more equitable distribution.

FUNDING

Japanese Ministry of Health, Labour, and Welfare and Meiji Seika Pharma.

Time-varying effects of COVID-19 vaccination on symptomatic and asymptomatic infections in a prospective university cohort in the USA

OBJECTIVES

Despite widespread vaccination programmes and consensus recommendations, the understanding of the durability of COVID-19 vaccination against ensuing infection and transmission at the individual level is incomplete. The objective of this study was to estimate the effects of time-varying covariates including time since vaccination and symptoms on subsequent positive SARS-CoV-2 test results and assess the stability of these effects between March 2020 and April 2022.

DESIGN

Prospective cohort study.

SETTING

Urban university in the USA.

PARTICIPANTS

Drexel University students, faculty, and staff (n=15 527) undergoing mandatory COVID-19 symptom tracking, testing and vaccinations.

INTERVENTION

Systematic symptom tracking and SARS-COV-2 testing starting in September 2020 and mandatory COVID-19 vaccination starting in September 2021.

MAIN OUTCOMES AND MEASURES

COVID-19 vaccine effectiveness modified by time since vaccination and symptoms.

RESULTS

Using fit-for-purpose digitally based symptom and vaccine tracking and mandatory comprehensive testing for SARS-CoV-2 infection, we estimate the time-dependent effects of vaccination, symptoms and covariates on the risk of infection with a Cox proportional hazards model based on calendar time scale. We found a strong protective effect of vaccination against symptomatic infection. However, there was strong evidence of a protective effect against infection only in the first 90 days after completed vaccination, and only against symptomatic versus asymptomatic infection. The overall estimated effect of vaccination within 30 days, including asymptomatic infections, was 37.3% (95% CI 26%, 47%). Vaccine effect modification by reported symptoms and time period was estimated, revealing the protective effect of vaccination within 90 days against symptomatic infection that varied from 90% (95% CI 84%, 94%) to 49%(95% CI -77%, 85%) across time periods.

CONCLUSIONS

This study is among the first to prospectively capture complete COVID-19 symptom, testing and vaccination data over a multiyear period. Overall effectiveness of the COVID-19 vaccine against subsequent infection, including transmissible asymptomatic infections, is modest and wanes after 90 days. Vaccination policies may need to take these issues into account.

Estimates of SARS-CoV-2 Infections and Population Immunity After the COVID-19 Pandemic in Austria: Analysis of National Wastewater Data

BACKGROUND

Postpandemic surveillance data on coronavirus disease 2019 (COVID-19) infections may help inform future public health policies regarding severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) testing, vaccinations, or other COVID-19 measures. We estimate the total SARS-CoV-2 infections in Austria after the end of the pandemic from wastewater data and utilize these estimates to calculate the average national levels of SARS-CoV-2 infection protection and COVID-19 death protection.

METHODS

We estimated the total SARS-CoV-2 infections in Austria after the end of the pandemic (5 May 2023, per World Health Organization) up to May 2024 from wastewater data using a previously published model. These estimates were used in an agent-based model (ABM) to estimate average national levels of SARS-CoV-2 infection protection and COVID-19 death protection, based on waning immunity estimates of infections and vaccination in previous literature.

RESULTS

We estimate approximately 3.2 million infections between 6 May 2023 and 23 May 2024, with a total of 17.8 million infections following 12 May 2020. The ABM estimates that the national average death protection was approximately 82% higher in May 2024 than before the pandemic. This represents a relative decrease of 8% since May 2023. It also shows that 95% of people in Austria were infected with SARS-CoV-2 at least once by May 2024. National infection protection remained relatively low after the onset of Omicron.

CONCLUSIONS

These findings should be considered for public health decisions on SARS-CoV-2 testing practices and vaccine booster administrations.

Cost-Effectiveness of Introducing Nuvaxovid to COVID-19 Vaccination in the United Kingdom: A Dynamic Transmission Model

Background/Objectives: Vaccination against SARS-CoV-2 remains a key measure to control COVID-19. Nuvaxovid, a recombinant Matrix-M-adjuvanted protein-based vaccine, showed similar efficacy to mRNA vaccines in clinical trials and real-world studies, with lower rates of reactogenicity. Methods: To support decision making on UK vaccine selection, a population-based compartmental dynamic transmission model with a cost-utility component was developed to evaluate the cost-effectiveness of Nuvaxovid compared with mRNA vaccines from a UK National Health Service perspective. The model was calibrated to official epidemiology statistics for mortality, incidence, and hospitalisation. Scenario and sensitivity analyses were conducted. Results: In the probabilistic base case, a Nuvaxovid-only strategy provided total incremental cost savings of GBP 1,338,323 and 1558 additional quality-adjusted life years (QALYs) compared with an mRNA-only vaccination strategy. Cost savings were driven by reduced cold chain-related operational costs and vaccine wastage, while QALY gains were driven by potential differences in vaccine tolerability. Probabilistic sensitivity analysis indicated an approximately 70% probability of cost-effectiveness with Nuvaxovid-only versus mRNA-only vaccination across most cost-effectiveness thresholds (up to GBP 300,000/QALY gained). Conclusions: Nuvaxovid remained dominant over mRNA vaccines in scenario analyses assessing vaccine efficacy waning, Nuvaxovid market shares, and the vaccinated population.

Novel mRNA vaccines induce potent immunogenicity and afford protection against tuberculosis

Introduction

Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis (TB), a disease with a severe global burden. The intractability of Mtb has prevented the identification of clear correlates of protection against TB and hindered the development of novel TB vaccines that are urgently required. Lipid nanoparticle (LNP)-formulated mRNA is a highly promising vaccine platform that has yet to be thoroughly applied to TB.

Methods

We selected five Mtb antigens (PPE15, ESAT6, EspC, EsxI, MetE) and evaluated their potential as LNP-formulated mRNA vaccines, both when each antigen was delivered individually, and when all five antigens were combined in a mix regimen (m-Mix).

Results

Each mRNA construct demonstrated unique cellular and humoral immunogenicity, and both m-Mix, as well as the single antigen EsxI, conferred significant protection in a murine Mtb challenge model. Whilst the potent immune responses of each mRNA were maintained when applied as a boost to BCG, there was no additional increase to the efficacy of BCG. Combination of m-Mix with a recombinant, replication-deficient chimpanzee adenovirus (ChAdOx1), in a heterologous prime-boost delivery (C-m-Mix), appeared to result in increased protection upon murine Mtb infection, than either regimen alone.

Discussion

This work warrants further investigation of LNP-formulated mRNA vaccines for TB, whilst indicating the potential of m-Mix and C-m-Mix to progress to further stages of vaccine development.

Effectiveness of AZD7442 (Tixagevimab/Cilgavimab) for Pre-Exposure Prophylaxis Against COVID-19 Hospitalization in Israel During the Omicron Sub-Variant Time Period

INTRODUCTION

The effectiveness of AZD7442 (tixagevimab/cilgavimab) against COVID-19 hospitalizations was determined at 3 and 6 months among immunocompromised individuals in Israel during different variant circulations.

METHODS

This was a retrospective cohort study using data from Clalit Health Services in Israel. Immunocompromised individuals eligible to receive AZD7442 300 mg between 15 February and 11 December 2022 were identified. Immunocompromised individuals receiving AZD7442 300 mg as pre-exposure prophylaxis (PrEP) were propensity score (PS)-matched 1:1 to unexposed individuals using a "rolling cohort" approach. Calendar time Cox proportional hazards regression models were performed with adjustment for post-matched unbalanced covariates to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

Overall, 2444 AZD7442-exposed immunocompromised individuals were PS-matched to unexposed individuals. In the matched population, up to 6 months of follow-up, AZD7442 300 mg presented an unadjusted HR (without adjustment for the unbalanced covariates) of 0.68 (95% CI 0.43-1.08) and covariate-adjusted HR of 0.64 (95% CI 0.40-1.03) against COVID-19 hospitalization. Covariate-adjusted instantaneous hazards plots showed that the effectiveness of AZD7442 300 mg waned from Day 90. Up to 3 months of follow-up, the unadjusted HR was 0.43 (95% CI 0.21-0.91) for AZD7442 300 mg against COVID-19 hospitalization in the matched population; there were insufficient events to allow covariate-adjusted analysis.

CONCLUSION

Our results suggest that AZD7442 300 mg reduced COVID-19 hospitalizations among immunocompromised individuals; however, the findings are limited by a lack of sufficient events to produce conclusive results.

Medical mistrust and vaccine-hesitant attitudes explain SARS-CoV-2 vaccination disparities in a mixed serostatus cohort

OBJECTIVES

To understand the extent of racial disparities in SARS-CoV-2 vaccination among PWH and those vulnerable to HIV infection and to estimate the contributions of medical mistrust and vaccine-hesitant attitudes to these disparities.

DESIGN

Quantitative data analyses in a racially and gender-diverse, mixed-serostatus prospective cohort, the Multicenter AIDS Cohort Study (MACS)/Women's Interagency HIV Study (WIHS) Combined Cohort Study.

METHODS

Interviewer-assisted questionnaires assessed SARS-CoV-2 vaccination, medical mistrust, and vaccine-hesitant attitudes from March 2021 to September 2022 ( n  = 3948). Longitudinal analyses assessed effects of sociodemographics on medical mistrust and vaccine-hesitant attitudes. A hierarchical multivariable logistic regression assessed effects of these co-factors on SARS-CoV-2 vaccination. Causal mediation models assessed whether medical mistrust mediated the relationship between Black identity and vaccine-hesitant attitudes, and vaccine-hesitant attitudes mediated the relationship between Black identity and SARS-CoV-2 nonvaccination.

RESULTS

Participants' mean age was 56.7; 55.3% were Black, 52.6% cisgender female, 62.6% PWH. 10.1% reported never receiving SARS-CoV-2 vaccinations (13.4% of Black and 4.5% of White participants). Black-identified participants had higher odds of nonvaccination than White participants [aOR = 1.72; 95% confidence interval (CI) 1.08-2.72]. Medical mistrust mediated the relationship between Black identity and vaccine-hesitant attitudes, accounting for 46% of the effect ( P  < 0.0001). Vaccine-hesitant attitudes mediated the relationship between Black identity and SARS-CoV-2 nonvaccination to the extent that 57.7% (95% CI 25.3-90.1%) of the disparity would be eliminated if vaccine-hesitant attitudes among Black respondents were reduced to levels reported among other racial groups.

CONCLUSION

Findings indicate a profound need to build trustworthy healthcare environments to combat medical mistrust and vaccine-hesitant attitudes in Black communities in the United States, including those affected by HIV.

Household transmission of Omicron variant of SARS-CoV-2 under conditions of hybrid immunity-a prospective study in Germany

PURPOSE

We investigated the protection offered by vaccinations and previous infections for the household transmission of Omicron variant of SARS-CoV-2.

METHODS

34,666 participants of the German DigiHero cohort study with two or more household members were invited to a prospective household transmission study between June and December 2022. In case of a positive SARS-CoV-2 test in a household, symptom diaries were completed for at least 14 days. Dry blood spots (DBS) were taken from all household members at the beginning and six to eight weeks later. DBS were analyzed for SARS-CoV-2 antibodies.

RESULTS

1191 individuals from 457 households participated. The risk of acquiring a SARS-CoV-2 infection decreased with higher S-titer levels at the time of exposure (from 80% at titer of 0 binding antibody units (BAU)/ml to 20% at titer of 3000 BAU/ml) and increased linearly with the time since vaccination/previous infection (20% for less than one month to 80% at one year). Transmission probability was also reduced when the symptoms of the primary case were mild and if preventive measures were implemented.

CONCLUSION

Vaccinations/previous infections offer a high protection against infection with the Omicron variant for a few months only, supporting the notion of seasonal circulation of the virus.

Safety and immunogenicity of Omicron protein vaccines in mRNA-vaccinated adolescents: A phase 3, randomised trial

OBJECTIVES

Safety and immunogenicity assessment of updated monovalent and bivalent SARS-CoV-2 vaccines in adolescents.

METHODS

This phase 3, double-blinded study randomised 12-<18-year-old participants, who received ≥2 prior doses of an approved/authorised mRNA-based COVID-19 vaccine, 1:1 to receive NVX-CoV2601 (XBB.1.5) or a bivalent vaccine (NVX-CoV2373 [Wuhan] + NVX-CoV2601). The primary immunogenicity endpoint was day-28 neutralising antibody (nAb) geometric mean titres (GMTs) against XBB.1.5. Safety endpoints were solicited reactogenicity ≤7 days and unsolicited adverse events (AEs) ≤28 days post-vaccination and frequency/severity of predefined AEs of special interest through day 180.

RESULTS

Of 401 randomised participants, nAb GMTs against XBB.1.5 increased (GMFR [95% CI]) for both NVX-CoV2601 (12.2 [9.5-15.5]) and the bivalent vaccine (8.4 [6.8-10.3]); post-vaccination responses to ancestral SARS-CoV-2 and the JN.1 variant were also observed. Increases in anti-spike IgG levels were comparable between the groups. Solicited and unsolicited AEs were mild to moderate, with similar occurrence among the groups. Severe and serious events were rare and unrelated to the study vaccines; no PIMMCs or myocarditis/pericarditis were reported.

CONCLUSIONS

NVX-CoV2601 elicited more robust antibody responses to XBB.1.5 and ancestral virus, compared with a bivalent formulation. The safety profile within each group was consistent with NVX-CoV2373, which contains ancestral recombinant spike protein.

Association between social activities and risk of COVID-19 in a cohort of healthcare personnel

Objective

Previous studies have linked social behaviors to COVID-19 risk in the general population. The impact of these behaviors among healthcare personnel, who face higher workplace exposure risks and possess greater prevention awareness, remains less explored.

Design

We conducted a Prospective cohort study from December 2021 to May 2022, using monthly surveys. Exposures included (1) a composite of nine common social activities in the past month and (2) similarity of social behavior compared to pre-pandemic. Outcomes included self-reported SARS-CoV-2 infection (primary)and testing for SARS-CoV-2 (secondary). Mixed-effect logistic regression assessed the association between social behavior and outcomes, adjusting for baseline and time-dependent covariates. To account for missed surveys, we employed inverse probability-of-censoring weighting with a propensity score approach.

Setting

An academic healthcare system.

Participants

Healthcare personnel.

Results

Of 1,302 healthcare personnel who completed ≥2 surveys, 244 reported ≥1 positive test during the study, resulting in a cumulative incidence of 19%. More social activities in the past month and social behavior similar to pre-pandemic levels were associated with increased likelihood of SARS-CoV-2 infection (recent social activity composite: OR = 1.11, 95% CI 1.02-1.21; pre-pandemic social similarity: OR = 1.14, 95% CI 1.07-1.21). Neither was significantly associated with testing for SARS-CoV-2.

Conclusions

Healthcare personnel social behavior outside work was associated with a higher risk for COVID-19. To protect the hospital workforce, risk mitigation strategies for healthcare personnel should focus on both the community and workplace.

Strength and durability of indirect protection against SARS-CoV-2 infection through vaccine and infection-acquired immunity

Early investigation revealed a reduced risk of SARS-CoV-2 infection among social contacts of COVID-19 vaccinated individuals, referred to as indirect protection. However, indirect protection from SARS-CoV-2 infection-acquired immunity and its comparative strength and durability to vaccine-derived indirect protection in the current epidemiologic context of high levels of vaccination, prior infection, and novel variants are not well characterized. Here, we show that both vaccine-derived and infection-acquired immunity independently yield indirect protection to close social contacts with key differences in their strength and waning. Analyzing anonymized SARS-CoV-2 surveillance data from 9,625 residents in California state prisons from December 2021 to December 2022, we find that vaccine-derived indirect protection against Omicron SARS-CoV-2 infection is strongest within three months of COVID-19 vaccination [30% (95% confidence interval: 20-38%)] with subsequent modest protection. Infection-acquired immunity provides 38% (24-50%) indirect protection for 6 months after SARS-CoV-2 infection, with moderate indirect protection persisting for over one year. Variant-targeted vaccines (bivalent formulation including Omicron subvariants BA.4/BA.5) confer strong indirect protection for at least three months [40% (3-63%)]. These results demonstrate that both vaccine-derived and infection-acquired immunity can reduce SARS-CoV-2 transmission which is important for understanding long-term transmission dynamics and can guide public health intervention, especially in high-risk environments such as prisons.

Dynamic Changes and Trends of SARS-CoV-2 Antibodies Induced by Infection and Vaccination Across Multiple Time Points

As the COVID-19 pandemic continues, increasingly complex vaccination and infection histories have made it urgent to investigate the antibody dynamics in populations with hybrid immunity. This study aimed to explore the multi-time-point dynamics of SARS-CoV-2 IgG antibody levels in a community-based population in Jiangsu Province, China, following the Omicron BA.5 wave, as well as the long-term persistence of IgG antibodies nearly 2 years postinfection. A total of 2737 participants across Jiangsu Province were followed up at three different time points over a 6-month period (December 2022-June 2023). Additionally, a cross-sectional serological survey was conducted in October 2024, involving 230 participants to assess long-term antibody persistence. We used generalized additive models to fit antibody dynamics curves, generalized linear mixed models to explore factors influencing antibody levels, and Kaplan-Meier survival analysis to estimate cumulative seroreversion rates. Our findings revealed that, following the large-scale Omicron BA.5 infections, over 85% of the population initially exhibited seropositive IgG levels. Older individuals (> 65 years) had significantly lower antibody levels and faster rates of decline compared to younger participants. Booster immunization reduced the risk of seroreversion by 59.79% (95% CI: 29.63%-76.46%), while individuals with multiple infections experienced slower antibody decay. In the cross-sectional survey conducted 22 months postinfection, the IgG seropositivity rate remained high, exceeding 98%, indicating sustained immunity at the population level. This study provides valuable insights into the dynamics and persistence of IgG antibody levels following large-scale infection. The results underscore the importance of tailored booster immunization strategies to sustain long-term immunity, especially in vulnerable groups like the elderly. Additionally, ongoing serological monitoring is essential for assessing population immunity and informing future vaccination strategies.

Effectiveness of COVID-19 vaccines against SARS-CoV-2 infection and severe outcomes in adults: a systematic review and meta-analysis of European studies published up to 22 January 2024

BACKGROUND

Up-to-date evidence from European studies on long-term vaccine effectiveness (VE) of COVID-19 vaccines is lacking. This review aimed to evaluate effectiveness and durability of primary vaccine series and boosters in preventing infection and severe outcomes in the European population.

METHODS

We conducted systematic searches of PubMed and Embase up to 22 January 2024. We included observational studies that evaluated VE against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or severe disease (hospitalisation, intensive care unit admission or death) for primary series and boosters in Europe. We applied a random-effects meta-analysis model.

RESULTS

We included 33 studies and over 56 million participants. The overall VE of the complete primary series against infection with any SARS-CoV-2 variant was 70.7%. VE was lower for Omicron, at 26.1%, than for pre-Omicron strains, at 77.0%. Over time, VE against infection by any variant decreased from 68.9% to 38.9% after 6 months. Boosters restored VE to 76.4% and maintained at 58.4% after 3 months. The overall VE of a complete primary series for severe outcomes due to any variant was 87.4%, with 93.3% for pre-Omicron and 62.8% for Omicron strains. Protection against severe outcomes declined less than for infection. 6 months after the primary series, the vaccine still provided over 50% protection against severe outcomes caused by Omicron. Boosters restored VE to 87.9% and maintained at 78.5% after 3 months.

CONCLUSION

VE against SARS-CoV-2 infection declines markedly with time and Omicron variants. Protection against severe outcomes was more durable and resistant to viral mutation. Boosters restored protection, emphasising the need for timely booster vaccination for vulnerable populations.

Longitudinal analysis of SARS-CoV-2 IgG antibody durability in Puerto Rico

Understanding the dynamics of antibody responses following vaccination and SARS-CoV-2 infection is important for informing effective vaccination strategies and other public health interventions. This study investigates SARS-CoV-2 antibody dynamics in a Puerto Rican cohort, analyzing how IgG levels vary by vaccination status and previous infection. We assess waning immunity and the distribution of hybrid immunity with the aim to inform public health strategies and vaccination programs in Puerto Rico and similar settings. We conducted a prospective, longitudinal cohort study to identify SARS-CoV-2 infections and related outcomes in Ponce, Puerto Rico, from June 2020-August 2022. Participants provided self-collected nasal swabs every week and serum every six months for RT-PCR and IgG testing, respectively. IgG reactivity against nucleocapsid (N) antigens, which generally indicate previous infection, and spike (S1) and receptor-binding domain (RBD) antigens, which indicate history of either infection or vaccination, was assessed using the Luminex Corporation xMAP® SARS-CoV-2 Multi-Antigen IgG Assay. Prior infection was defined by positive RT-PCRs, categorized by the predominant circulating SARS-CoV-2 variant at the event time. Demographic information, medical history, and COVID-19 vaccination history were collected through standardized questionnaires. Of 882 participants included in our analysis, 34.0% experienced at least one SARS-CoV-2 infection, with most (78.7%) occurring during the Omicron wave (December 2021 onwards). SARS-CoV-2 antibody prevalence increased over time, reaching 98.4% by the final serum collection, 67.0% attributable to vaccination alone, 1.6% from infection alone, and 31.4% from both. Regardless of prior infection status, RBD and S1 IgG levels gradually declined following two vaccine doses. A third dose boosted these antibody levels and showed a slower decline over time. N-antibody levels peaked during the Omicron surge and waned over time. Vaccination in individuals with prior SARS-CoV-2 infection elicited the highest and most durable antibody responses. N or S1 seropositivity was associated with lower odds of a subsequent positive PCR test during the Omicron period, with N antibodies showing a stronger association. By elucidating the differential decay of RBD and S1 antibodies following vaccination and the complexities of N-antibody response following infection, this study in a Puerto Rican cohort strengthens the foundation for developing targeted interventions and public health strategies.

Higher Post-Acute Health Care Costs Following SARS-CoV-2 Infection Among Adults in Ontario, Canada

Purpose and Introduction

Growing evidence suggests SARS-CoV-2 infection increases the risk of long term cardiovascular, neurological, and other effects. However, post-acute health care costs following SARS-CoV-2 infection are not known.

Patients and Statistical Methods

Beginning 56 days following SARS-CoV-2 polymerase chain reaction (PCR) testing, we compared person-specific total and component health care costs (2020 CAD$) for the first year of follow-up at the mean and 99th percentiles of health care costs for matched test-positive and test-negative adults in Ontario, Canada, between January 1, 2020, and March 31, 2021. Matching included demographics, baseline clinical characteristics, and two-week time blocks.

Results

For 531,182 people, mean person-specific total health care costs were $513.83 (95% CI $387.37-$638.40) higher for test-positive females and $459.10 (95% CI $304.60-$615.32) higher for test-positive males, which were driven by hospitalization, long-term care, and complex continuing care costs. At the 99th percentile of each subgroup, person-specific health care costs were $12,533.00 (95% CI $9008.50-$16,473.00) higher for test-positive females and $14,604.00 (95% CI $9565.50-$19,506.50) for test-positive males, driven by hospitalization, specialist (males), and homecare costs (females). Cancer costs were lower. Six-month and 1-year cost differences were similar.

Conclusion

Post-acute health care costs after a positive SARS-CoV-2 PCR test were significantly higher than matched test-negative individuals, and these increased costs persisted for at least one year. The largest increases health care costs came from hospitalizations, long-term care, complex continuing care, followed by outpatient specialists (for males) and homecare costs (for women). Given the magnitude of ongoing viral spread, policymakers, clinicians, and patients should be aware of higher post-acute health care costs following SARS-CoV-2 infection.

Longitudinal effects of SARS-CoV-2 breakthrough infection on imprinting of neutralizing antibody responses

BACKGROUND

The impact of the infecting SARS-CoV-2 variant of concern (VOC) and the vaccination status was determined on the magnitude, breadth, and durability of the neutralizing antibody (nAb) profile in a longitudinal multicentre cohort study.

METHODS

173 vaccinated and 56 non-vaccinated individuals were enrolled after SARS-CoV-2 Alpha, Delta, or Omicron infection and visited four times within 6 months and nAbs were measured for D614G, Alpha, Delta, BA.1, BA.2, BA.5, BQ.1.1, XBB.1.5 and JN.1.

FINDINGS

Magnitude-breadth-analysis showed enhanced neutralization capacity in vaccinated individuals against multiple VOCs. Longitudinal analysis revealed sustained neutralization magnitude-breadth after antigenically distant Delta or Omicron breakthrough infection (BTI), with triple-vaccinated individuals showing significantly elevated titres and improved breadth. Antigenic mapping and antibody landscaping revealed initial boosting of vaccine-induced WT-specific responses after BTI, a shift in neutralization towards infecting VOCs at peak responses and an immune imprinted bias towards dominating WT immunity in the long-term. Despite that bias, machine-learning models confirmed a sustained shift of the immune-profiles following BTI.

INTERPRETATION

In summary, our longitudinal analysis revealed delayed and short lived nAb shifts towards the infecting VOC, but an immune imprinted bias towards long-term vaccine induced immunity after BTI.

FUNDING

This work was funded by the Bavarian State Ministry of Science and the Arts for the CoVaKo study and the ForCovid project. The funders had no influence on the study design, data analysis or data interpretation.

COVID-19 Vaccination Recommendations for 2024-2025 in Korea

The Korean Society of Infectious Diseases has been regularly publishing guidelines for adult immunization since 2007. Following the release of coronavirus disease 2019 (COVID-19) vaccination recommendations in 2023, significant changes have occurred due to the emergence of new variant strains and the waning immunity from previous vaccinations. This article provides a comprehensive update as of November 2024, incorporating the latest evidence and guidelines. Focusing on the 2024-2025 season, this article reviews vaccines currently authorized in Korea and assesses their effectiveness against the predominant JN.1 lineage variants. The updated recommendations prioritize high-risk groups, including adults aged 65 and older, individuals with underlying medical conditions, residents of facilities vulnerable to infection, pregnant women, and healthcare workers, for vaccination with updated vaccines targeting the JN.1 strain. Additionally, COVID-19 vaccination is available for all individuals aged 6 months and older. For most adults, a single-dose strategy is emphasized, while tailored schedules may be recommended for immunocompromised individuals. This update aims to optimize vaccination strategies in Korea to ensure comprehensive protection for high-risk populations.

Real-time estimates of the emergence and dynamics of SARS-CoV-2 variants of concern: A modeling approach

The emergence of SARS-CoV-2 variants of concern (VOCs) punctuated the dynamics of the COVID-19 pandemic in multiple occasions. The stages subsequent to their identification have been particularly challenging due to the hurdles associated with a prompt assessment of transmissibility and immune evasion characteristics of the newly emerged VOC. Here, we retrospectively analyze the performance of a modeling strategy developed to evaluate, in real-time, the risks posed by the Alpha and Omicron VOC soon after their emergence. Our approach utilized multi-strain, stochastic, compartmental models enriched with demographic information, age-specific contact patterns, the influence of non-pharmaceutical interventions, and the trajectory of vaccine distribution. The models' preliminary assessment about Omicron's transmissibility and immune evasion closely match later findings. Additionally, analyses based on data collected since our initial assessments demonstrate the retrospective accuracy of our real-time projections in capturing the emergence and subsequent dominance of the Alpha VOC in seven European countries and the Omicron VOC in South Africa. This study shows the value of relatively simple epidemic models in assessing the impact of emerging VOCs in real time, the importance of timely and accurate data, and the need for regular evaluation of these methodologies as we prepare for future global health crises.

Epidemiological comparison of emergency department presentations with seasonal influenza or COVID-19 and an outcome of intensive care admission or death: A population-based records linkage study in New South Wales, Australia

BACKGROUND

COVID-19 and seasonal influenza are endemic causes of morbidity and mortality. This study aimed to compare the epidemiology of severe illness and risk of death among patients following emergency department (ED) presentation with either infection.

METHODS

De-identified, population-based, emergency department records in New South Wales, Australia, were probabilistically linked to population-level health outcome databases for the period 1 January 2015 to 28 February 2023. Included were patients allocated an ED diagnosis consistent with an acute respiratory infection. Logistic regression was used to examine the association of infecting virus with risk of a severe outcome (intensive care unit admission or death).

RESULTS

Influenza infection was notified in 2335 and COVID-19 in 5053 patients with a severe outcome. The age distribution was similar for both viruses, except in <15-year-olds, where severe influenza was nearly three times more frequent. Overall, the odds of death among patients with COVID-19 was 1.65 (95% CI 1.43, 1.89) times higher than among those with influenza. This declined to 1.49 (95% CI 1.08, 2.06) times during the COVID-19 Omicron variant period.

CONCLUSIONS

The Omicron variant arrived when background population COVID-19 vaccination coverage was >90%. Despite that, death was more frequent for COVID-19 than influenza.

Avidity maturation of humoral response following primary and booster doses of BNT162b2 mRNA vaccine among nursing home residents and healthcare workers

Infections, despite vaccination, can be clinically consequential for frail nursing home residents (NHR). Poor vaccine-induced antibody quality may add risk for such subsequent infections and more severe disease. We assessed antibody binding avidity, as a surrogate for antibody quality, among NHR and healthcare workers (HCW). We longitudinally sampled 112 NHR and 52 HCWs who received the BNT162b2 mRNA vaccine after each dose up to the Wuhan-BA.4/5-based Omicron bivalent boosters. We quantified anti-spike, anti-receptor binding domain (RBD), and avidity levels to the ancestral Wuhan, Delta, and Omicron BA.1 & 4/5 strains. The primary vaccination series produced substantial anti-spike and RBD levels which were low in avidity against all strains tested. Antibody avidity progressively increased in the 6-8 months that followed. Avidity significantly increased after the 1st booster but not for subsequent boosters. This study underscores the importance of booster vaccination among NHR and HCWs. The 1st booster dose increases avidity, increasing vaccine-induced functional antibody. The higher cross-reactivity of higher avidity antibodies to other SARS-CoV-2 strains should translate to better protection from ever-evolving strains. Higher avidities may help explain how the vaccine's protective effects persist despite waning antibody titers after each vaccine dose.

Challenges in conducting efficacy trials for new COVID-19 vaccines in developed countries

The protection from COVID-19 vaccination wanes a few months post-administration of the primary vaccination series or booster doses. New COVID-19 vaccine candidates aiming to help control COVID-19 should show long-term efficacy, allowing a possible annual administration. Until correlates of protection are strongly associated with long-term protection, it has been suggested that any new COVID-19 vaccine candidate must demonstrate at least 75% efficacy (although a 40%-60% efficacy would be sufficient) at 12 months in preventing illness in all age groups within a large randomized controlled efficacy trial. This article discusses four of the many scientific, ethical, and operational challenges that these trials will face in developed countries, focusing on a pivotal trial in adults. These challenges are (1) the comparator and trial population; (2) how to enroll sufficient numbers of adult participants of all age groups considering that countries will recommend COVID-19 booster doses to different populations; (3) whether having access to a comparator booster for the trial is actually feasible; and (4) the changing epidemiology of severe acute respiratory syndrome coronavirus 2 across countries involved in the trial. It is desirable that regulatory agencies publish guidance on the requirements that a trial like the one discussed should comply with to be acceptable from a regulatory standpoint. Ideally, this should happen even before there is a vaccine candidate that could fulfill the requirements mentioned above, as it would allow an open discussion among all stakeholders on its appropriateness and feasibility.