Early COVID-19 vaccine effectiveness of XBB.1.5 vaccine against hospitalisation and admission to intensive care, the Netherlands, 9 October to 5 December 2023

Comparative effectiveness of Omicron XBB 1.5-adapted COVID-19 vaccines: a systematic literature review and network meta-analysis

INTRODUCTION

Comparative effectiveness data of COVID-19 vaccines remain limited. We conducted a systematic review and network meta-analysis (NMA) feasibility assessment of effectiveness studies of Omicron-adapted COVID-19 vaccines.

RESEARCH DESIGN AND METHODS

Searches in MEDLINE and Embase up to February 2025 identified studies comparing the effectiveness of Omicron-adapted COVID-19 vaccines, either directly or against no recent vaccine. Two investigators independently selected articles reporting adjusted vaccine effectiveness (VE). A feasibility assessment determined the appropriateness of a common comparator and evaluated effect modifiers (EMs). Data extraction and risk-of-bias assessment were performed by one investigator and validated by a second investigator. Bayesian NMAs using random-effects models were performed for base-case analyses, data permitting.

RESULTS

The review identified 25 studies for Omicron-adapted COVID-19 vaccines: 16 for XBB formulations, eight of which were included in NMAs, all for mRNA formulations, representing 29.9 million participants. BNT162b2 had the largest evidence base. Comparisons between XBB.1.5-adapted BNT162b2 (Comirnaty) and mRNA-1273 (Spikevax) found that both vaccines are effective and comparable against XBB-related hospitalizations, infections, and medically attended visits in adults Among elderly, the estimated effectiveness against XBB-related hospitalizations favored BNT162b2.

CONCLUSIONS

Findings of this NMA of observational studies support the effectiveness of XBB.1.5-adapted mRNA vaccines. Limitations included assumptions on EMs and sparse evidence networks.

Estimating the potential public health and economic impact of vaccination strategies with an adapted vaccine in Colombia using a combined Markov-decision tree model

BACKGROUND

Using adapted COVID-19 vaccines targeting current variants in circulation is necessary for addressing the dynamic evolution of the SARS-CoV-2 virus and protecting against emerging variants. This study evaluated the impact of various vaccination strategies with an adapted vaccine in Colombia.

RESEARCH DESIGN AND METHODS

Using a previously published combined Markov-decision tree model adapted for the Colombia context, this study estimated the outcomes of different vaccination strategies targeting various age and risk groups. The model used age-specific epidemiology, clinical, cost, and quality of life inputs derived from the published literature and national surveillance data. Scenario and sensitivity analyses were conducted to assess uncertainty.

RESULTS

Compared to no vaccination, the vaccination strategy targeting older adults aged ≥65 years and the high-risk population was estimated to prevent 306,460 symptomatic cases, 5,200 hospitalizations, 3,381 deaths, and 39,454 lost QALYs, translating to total direct and societal cost savings of USD 70,840,305 and USD 128,918,995, respectively. These gains were further increased by expanding vaccination to additional age groups. Results were most sensitive to parameters for the attack rate and duration of protection.

CONCLUSIONS

Implementing vaccination strategies targeting a broader age range with an adapted vaccine would result in considerable health and economic benefits in Colombia.

Modeling the potential public health and economic impact of COVID-19 vaccination strategies using an adapted vaccine in Peru

BACKGROUND

This study evaluated the impact of various vaccination strategies using an adapted vaccine in Peru.

RESEARCH DESIGN AND METHODS

Using a previously published combined Markov-decision-tree model adapted for Peru, this study estimated the outcomes of different vaccination strategies targeting various age and risk groups. The model used age-specific epidemiology, clinical, cost, and quality-of-life inputs derived from the published literature and national surveillance data. Sensitivity analyses were conducted to assess uncertainty.

RESULTS

The vaccination strategy targeting older adults aged ≥ 60 years and the high-risk population between 12 and 59 years old with a 24% vaccine uptake was estimated to prevent 78,483 symptomatic cases, 2,962 hospitalizations, 103 deaths, and 2,913 lost QALYs compared with no vaccination, translating to an incremental decrease of $12,856,654 in total direct costs and an incremental decrease of $35,090,748 in total societal costs. These gains were further increased by expanding vaccination to additional age groups and increasing vaccine uptake.

CONCLUSIONS

Vaccination in the population aged ≥ 60 years and the high-risk population between 12 and 59 years old in Peru was projected to yield substantial health and economic benefits. The impact could be substantially increased by expanding eligibility to younger age groups and increasing vaccine uptake.

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 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.

Are Updated COVID-19 Vaccines Still Relevant for All Adult Age Groups? An Economic Evaluation of the Monovalent XBB.1.5 Vaccine in Australia

OBJECTIVES

There is a progressive decline in the relative effectiveness of updated COVID-19 vaccines. Surveillance reports in Australia have also shown a wide variation in the disease severity and mortality across age groups. This study aimed to perform a cost-utility analysis of the monovalent XBB.1.5 vaccine relative to no updated booster vaccine between September 2023 and August 2024.

METHODS

A cost-utility analysis was performed using a Markov model from the healthcare system perspective for 3 different age groups (18-64, 65-74, and ≥75 years). Costs and outcomes with the monovalent XBB.1.5 vaccine were compared with no updated booster dose for 1 year. Health outcomes were expressed as quality-adjusted life years (QALYs), whereas costs were presented in 2023 Australian dollars. Aggregate distributional cost-effectiveness analysis and sensitivity analyses were performed. The willingness-to-pay threshold was set at A$50 000/QALY.

RESULTS

The updated vaccine was dominant for the 18 to 64 years group and cost-effective for the 65 to 74 years group (incremental cost-effectiveness ratio [ICER] = A$10 786/QALY) and ≥75 years group (ICER = A$36,531/QALY) relative to no updated booster vaccine. The major determinants of the ICER was the vaccine uptake rate. There was inequality in health benefits between the older First Nations versus nonindigenous Australians. The results were robust to simultaneous changes in the parameters' values.

CONCLUSIONS

The monovalent XBB.1.5 vaccine is cost-effective and still relevant for all adult age groups in Australia. Based on current evidence, the study findings support the promotion of booster vaccination for Australian adults.

Effectiveness of BNT162b2 XBB.1.5 vaccine in immunocompetent adults using tokenization in two U.S. states

BACKGROUND

Data describing the effectiveness of COVID-19 vaccines during the 2023-2024 fall and winter viral respiratory season are lacking. We estimated BNT162b2 XBB.1.5 vaccine effectiveness (VE) against COVID-19-associated hospital admission and emergency department (ED) visits in two heterogenous U.S. States.

METHODS

We conducted a retrospective cohort study among immunocompetent non-pregnant adults ≥18 years of age between September 25, 2023, and March 31, 2024 who were residents of California or Louisiana and enrolled in health insurance plans reporting to HealthVerity. Receipt of BNT162b2 XBB.1.5 vaccine was determined using State vaccine registry data (in addition to health insurance claims) and measured as a time-varying exposure. VE against COVID-19-associated hospital admission and ED visits was measured as 1- adjusted hazard ratio from Cox proportional hazards models. Models were adjusted for age, sex, State, insurance payor, presence of any condition(s) indicating CDC-defined high risk for severe COVID-19, wellness visit, influenza vaccination, outpatient visits, emergency department visits, and whether they had medically attended COVID-19 in the 91 to 365 days prior to index.

RESULTS

Overall, 6,344,448 individuals met selection criteria. Median age was 40 years and 54% were female. By the end of follow-up (median 6.3 months), 254,068 (4%) had received a BNT162b2 XBB.1.5 vaccine; 2346 (of whom 68 received BNT162b2 XBB.1.5 vaccine and 2278 did not) and 9327 (of whom 135 received BNT162b2 XBB.1.5 vaccine and 9192 did not) experienced a COVID-19-associated hospital admission and ED visit, respectively. VE was 36% (95% confidence interval [CI]: 18-50%) and 45% (95% CI: 34-54%) against COVID-19-associated hospital admission and ED visits, respectively. Prior formulations offered no significant residual protection.

DISCUSSION

BNT162b2 XBB.1.5 vaccine provided significant additional protection for immunocompetent adults against COVID-19-associated hospital admission and emergency department visits during the 2023-2024 fall and winter respiratory virus season. This study is registered on clinicaltrials.gov as NCT06199934.

Comparison of two methods for the estimation of COVID-19 vaccine effectiveness of the autumnal booster within the VEBIS-EHR network in 2022/23

Within an infrastructure to monitor vaccine effectiveness (VE) against hospitalization due to COVID-19 and COVID-19 related deaths from November 2022 to July 2023 in seven countries in real-world conditions (VEBIS network), we compared two approaches: (a) estimating VE of the first, second or third COVID-19 booster doses administered during the autumn of 2022, and (b) estimating VE of the autumn vaccination dose regardless of the number of prior doses (autumnal booster approach). Retrospective cohorts were constructed using Electronic Health Records at each participating site. Cox regressions with time-changing vaccination status were fit and site-specific estimates were combined using random-effects meta-analysis. VE estimates with both approaches were mostly similar, particularly shortly after the start of the vaccination campaign, and showed a similar timing of VE waning. However, autumnal booster estimates were more precise and showed a clearer trend, particularly compared to third booster estimates, as calendar time increased after the vaccination campaign and during periods of lower SARS-CoV-2 activity. Moreover, the decrease in protection by increasing calendar time was more clear and precise than when comparing protection by number of doses. Therefore, estimating VE under an autumnal booster framework emerges as a preferred method for future monitoring of COVID-19 vaccination campaigns.

Prospective cohort study of fatigue before and after SARS-CoV-2 infection in the Netherlands

Fatigue is one of the most common persistent symptoms of SARS-CoV-2 infection. We aimed to assess fatigue during and after a SARS-CoV-2 infection by age, sex, presence of a medical risk condition, SARS-CoV-2 variant and vaccination status, accounting for pre-infection fatigue and compared with uninfected individuals. We used data from an ongoing prospective cohort study in the Netherlands (VASCO). We included 22,705 first infections reported between 12 July 2021 and 9 March 2024. Mean fatigue scores increased during infection, declined rapidly in the first 90 days post-infection, but remained elevated until at least 270 days for Delta and 120 days for Omicron infections. Prevalence of severe fatigue was 18.5% before first infection. It increased to 24.4% and 22.5% during acute infection and decreased to 21.2% and 18.9% at 90 days after Delta and Omicron infection, respectively. The prevalence among uninfected participants was lower than among matched Delta-infected participants during the acute phase of the infection and 90 days post-infection. For matched Omicron-infected individuals this was only observed during the acute phase. We observed no differences in mean post- vs pre-infection fatigue scores at 90-270 days post-infection by vaccination status. The impact of SARS-CoV-2 infection on the prevalence of severe fatigue was modest at population level, especially for Omicron.

XBB.1.5 mRNA COVID-19 vaccine protection against inpatient or emergency department visits among adults infected with SARS-CoV-2 JN.1 and XBB-lineage variants

As part of a multi-state viral genomic surveillance program, we conducted a case-only analysis to evaluate the effectiveness of XBB.1.5-adapated mRNA vaccines in preventing severe illness among individuals with medically attended SARS-CoV-2 infection. We compared prior receipt of an XBB.1.5-adapted mRNA vaccine between SARS-CoV-2-infected adults with inpatient or emergency department (ED) visits (as a proxy for severe illness) vs those with outpatient visits (as a proxy for mild illness). Among 6,551 patients between September 2023 and January 2024, 6.1% with inpatient or ED visits vs 12.0% with outpatient visits had received XBB.1.5 vaccination (adjusted odds ratio [aOR]=0.41; 95% confidence interval [CI]: 0.32-0.53). This protective association was weaker among JN.1 (aOR=0.62; 95% CI: 0.40-0.96) vs XBB-lineage (aOR=0.28; 95% CI: 0.18-0.43) variant infections (interaction, p=0.003). XBB.1.5 vaccines protect against severe illness, but protection may be weaker against JN.1 vs XBB-lineage variants. This study highlights the need for COVID-19 vaccines to be routinely updated to align with circulating strains and for individuals to stay up to date with recommended vaccines.

Effectiveness of the BNT162b2 XBB.1.5-adapted vaccine against COVID-19 hospitalization related to the JN.1 variant in Europe: a test-negative case-control study using the id.DRIVE platform

Background

Prior studies have reported lower effectiveness of XBB.1.5-adapted vaccines against hospitalization related to the Omicron JN.1 variant than the XBB variant. This study evaluated the effectiveness and durability of the BNT162b2 XBB.1.5-adapted vaccine against JN.1-related hospitalization during the 2023-2024 season in Europe.

Methods

A test-negative case-control study was carried out in adults (≥18 y) hospitalized between 2 October 2023 and 2 April 2024 with severe acute respiratory infection (SARI) within the id.DRIVE partnership. This study included nine sites across Belgium, Germany, Italy, and Spain. Cases had a laboratory-confirmed JN.1 infection or a positive SARS-CoV-2 test with symptom onset during JN.1 predominance; controls had a negative SARS-CoV-2 test and symptom onset during JN.1 predominance. The primary objective was to estimate BNT162b2 XBB.1.5-adapted vaccine effectiveness (VE) against COVID-19 hospitalization. One case was matched with up to four controls, according to symptom onset date and site. Multivariable analyses were adjusted for symptom onset date, age, sex, and number of chronic conditions.

Findings

Among 308 test-positive cases and 1117 test-negative controls, BNT162b2 XBB.1.5-adapted VE against hospitalization compared to no vaccination this season was 53.8% (95% CI 38.4-65.4) after a median of 63 days following vaccination. Protection was sustained through five months; VE was 52.2% (95% CI 41.3-61.1) 2 to <4 weeks after vaccination, 48.9% (95% CI 17.9-68.2) at 4 to <8 weeks, and ranged from 54.6% to 59.5% at 4-week intervals from 8 to <22 weeks.

Interpretation

BNT162b2 XBB.1.5-adapted vaccine provided protection against JN.1-related hospitalization, regardless of prior vaccination history, with no evidence of waning through five months. These data support yearly vaccination against COVID-19 to prevent severe illness during the respiratory virus season.

Funding

Pfizer.

Impact of the 2023/24 autumn-winter COVID-19 seasonal booster campaign in preventing severe COVID-19 cases in Italy (October 2023-March 2024)

We assessed the impact of the 2023/2024 COVID-19 vaccination campaign in Italy by estimating the number of averted COVID-19 severe cases (i.e. COVID-19 associated hospitalisations or deaths) between October 2023 and March 2024, in those aged ≥60 years. We estimated that 565 (95 % CI: 497-625) cases, corresponding to 2.1 % (95 % CI: 1.8-2.3) of the expected cases without a vaccination campaign, were averted. We simulated three vaccination coverage scenarios: 50 %, 75 %, 90 % (versus the observed 10.7 %), finding that 9.7 % (95 % CI: 8.5-10.7); 14.5 % (95 % CI: 12.8-16.1); and 17.4 % (95 % CI: 15.3-19.3) of the expected cases would have been averted, respectively.

COVID-19 vaccine effectiveness against SARS-CoV-2-confirmed hospitalisation in the eastern part of the WHO European Region (2022-2023): a test-negative case-control study from the EuroSAVE network

Background

Understanding COVID-19 vaccine effectiveness (VE) in preventing severe disease is critical to inform vaccine policy. We used the test-negative design to estimate VE against SARS-CoV-2-confirmed hospitalisation in adults ≥18 years in the eastern WHO European Region.

Methods

We included patients hospitalised for severe acute respiratory infection (SARI) at sentinel surveillance sites in Albania, Georgia, Kyrgyzstan, North Macedonia, Serbia, and in Kosovo. We collected demographic information, COVID-19 vaccination history, and tested respiratory samples for SARS-CoV-2 by RT-PCR. We calculated VE of any vaccine dose received within 12 months (Annual VE) as [(1 - adjusted Odds Ratio) x 100%] using a one-stage pooled analysis. The reference group included unvaccinated individuals and those who received their last vaccine >12 months before symptom onset.

Findings

During 1 January 1, 2022-November 20, 2023, of 5162 patients, 57.0% (2942) were unvaccinated, 2.5% (129) received only one dose, 26.0% (1340) received only two doses (originally considered a primary series vaccine (PS)), 13.2% (683) received three doses only, and 1.3% (68) received four doses. Most PS vaccines and boosters were BNT162b2 (46.4% (622/1340) and 64.9% (443/683), respectively) and CoronaVac (23.0% (309/1340) and 18.3% (125/683)). No patients received Ad26.COV2.S (Johnson and Johnson) vaccines. Overall, 1009/5162 (19.5%) patients were SARS-CoV-2-positive. VE was 60.1% (95% Confidence Interval (CI) 12.4-81.8) for last vaccine received 14-89 days before symptom onset, 60.0% (95% CI 32.2-76.4) for 90-179 days, 7.0% (95% CI -28.5 to 32.7) for 180-269 days, and -5.4% (95% CI -43.8 to 22.8) for 270-365 days.).

Interpretation

During nearly two years of Omicron circulation in the eastern WHO European Region, COVID-19 vaccination reduced the risk of hospitalisations by more than half for 6 months following vaccination.

Funding

This study was funded by the World Health Organization, Regional Office for Europe through a cooperative agreement with the U.S. Centers for Disease Control and Prevention.

Effectiveness of the 2023-2024 Omicron XBB.1.5-containing mRNA COVID-19 Vaccine (mRNA-1273.815) in Preventing COVID-19-related Hospitalizations and Medical Encounters Among Adults in the United States

Background

This study aimed to evaluate the vaccine effectiveness (VE) of mRNA-1273.815, a 2023-2024 Omicron XBB.1.5-containing mRNA COVID-19 vaccine, at preventing COVID-19-related hospitalizations and any medically attended COVID-19 in adults.

Methods

In a linked electronic health record-claims dataset, we identified US adults (≥18 years) who received the mRNA-1273.815 vaccine (exposed cohort) between 12 September and 15 December 2023, matched 1:1 to individuals who did not receive a 2023-2024 updated COVID-19 vaccine (unexposed cohort). Cohorts were balanced using inverse probability of treatment weighting on demographics, vaccination and infection history, and underlying medical conditions. Study cohorts were followed until 31 December 2023 for COVID-19-related hospitalizations and medically attended COVID-19. Cox regression was used to estimate hazard ratios and VE. Subgroup analyses were performed for adults ≥50 years, adults ≥65 years, and individuals with underlying medical conditions.

Results

Overall, 859 335 matched pairs of mRNA-1273.815 recipients and unexposed adults were identified. The mean (standard deviation) age was 63 (16) years. More than 60% of individuals in both cohorts had an underlying medical condition. Among the overall adult population, VE was 60.2% (95% confidence interval, 53.4-66.0) against COVID-19-related hospitalization and 33.1% (30.2-35.9) against medically attended COVID-19 over a median follow-up of 63 (interquartile range: 44-78) days. VE estimates by age and underlying medical conditions were similar.

Conclusions

These results demonstrate the significant protection provided by mRNA-1273.815 against COVID-19-related hospitalizations and any medically attended COVID-19 in adults, regardless of vaccination history, and support Centers for Disease Control and Prevention recommendations to stay up-to-date with COVID-19 vaccination to prevent COVID-19-related outcomes, including hospitalizations.

Human and hamster sera correlate well in identifying antigenic drift among SARS-CoV-2 variants, including JN.1

Antigenic assessments of SARS-CoV-2 variants inform decisions to update COVID-19 vaccines. Primary infection sera are often used for assessments, but such sera are rare due to population immunity from SARS-CoV-2 infections and COVID-19 vaccinations. Here, we show that neutralization titers and breadth of matched human and hamster pre-Omicron variant primary infection sera correlate well and generate similar antigenic maps. The hamster antigenic map shows modest antigenic drift among XBB sub-lineage variants, with JN.1 and BA.4/BA.5 variants within the XBB cluster, but with fivefold to sixfold antigenic differences between these variants and XBB.1.5. Compared to sera following only ancestral or bivalent COVID-19 vaccinations, or with post-vaccination infections, XBB.1.5 booster sera had the broadest neutralization against XBB sub-lineage variants, although a fivefold titer difference was still observed between JN.1 and XBB.1.5 variants. These findings suggest that antibody coverage of antigenically divergent JN.1 could be improved with a matched vaccine antigen.IMPORTANCEUpdates to COVID-19 vaccine antigens depend on assessing how much vaccine antigens differ antigenically from newer SARS-CoV-2 variants. Human sera from single variant infections are ideal for discriminating antigenic differences among variants, but such primary infection sera are now rare due to high population immunity. It remains unclear whether sera from experimentally infected animals could substitute for human sera for antigenic assessments. This report shows that neutralization titers of variant-matched human and hamster primary infection sera correlate well and recognize variants similarly, indicating that hamster sera can be a proxy for human sera for antigenic assessments. We further show that human sera following an XBB.1.5 booster vaccine broadly neutralized XBB sub-lineage variants but titers were fivefold lower against the more recent JN.1 variant. These findings support updating the current COVID-19 vaccine variant composition and developing a framework for assessing antigenic differences in future variants using hamster primary infection sera.

Comparative effectiveness of monovalent XBB.1.5 containing covid-19 mRNA vaccines in Denmark, Finland, and Sweden: target trial emulation based on registry data

ABSTRACT

Objective

To estimate the effectiveness of vaccination with a monovalent covid-19 mRNA vaccine containing the omicron XBB.1.5 subvariant against severe covid-19 disease in Denmark, Finland, and Sweden.

Design

Target trial emulation based on registry data.

Setting

Denmark, Finland, and Sweden, 1 October 2023 to 21 April 2024.

Participants

Source population of 3 898 264 individuals eligible for vaccination with the XBB.1.5 containing covid-19 mRNA vaccine at the start of the study on 1 October 2023. Study cohort comprised 1 876 282 recipients of an XBB.1.5 containing vaccine during the study period matched with 1 876 282 non-recipients. Individuals were aged ≥65 years (mean age 75.4 years, standard deviation 7.4 years) and had received at least four doses of a previous covid-19 vaccine.

Main outcome measures

Cumulative incidences of hospital admissions and deaths related to covid-19 in a follow-up period of 24 weeks after immunisation (defined as one week after vaccination) in recipients of an XBB.1.5 containing covid-19 mRNA vaccine and matched non-recipients. Cumulative incidences were used to calculate comparative vaccine effectiveness (1-risk ratio) and risk differences.

Results

The associated comparative vaccine effectiveness was 57.9% (95% confidence interval (CI) 49.9% to 65.8%) against hospital admission for covid-19 (1085 v 2635 events) and 75.2% (70.6% to 79.9%) against deaths related to covid-19 disease (348 v 1458 events) after 24 weeks of follow-up. This result corresponded to 154.7 (95% CI 78.3 to 231.0) hospital admissions for covid-19 and 120.3 (110.5 to 130.2) deaths prevented per 100 000 individuals who were vaccinated with an XBB.1.5 containing vaccine. The associated comparative vaccine effectiveness was similar irrespective of sex, age group (65-74 v ≥75 years), number of doses of previous covid-19 vaccines, subgroup of co-administered seasonal influenza vaccines, and period of when either the omicron XBB or BA.2.86 sublineage was predominant. Although the observed reduction in risk was highest during the first weeks after vaccination, comparative vaccine effectiveness was well maintained after 24 weeks of follow-up.

Conclusions

In this study, in adults aged ≥65 years, vaccination with a monovalent XBB.1.5 containing covid-19 mRNA vaccine was associated with reduced rates of hospital admissions for covid-19 and deaths related to covid-19, during the autumn and winter of 2023-24 in Denmark, Finland, and Sweden.

Effectiveness of BNT162b2 XBB vaccine in the US Veterans Affairs Healthcare System

Data evaluating effectiveness of XBB.1.5-adapted vaccines against JN.1-related endpoints are scarce. This nationwide test-negative case-control study within the US Veterans Affairs Healthcare System aims to estimate vaccine effectiveness (VE) of BNT162b2 XBB.1.5-adapted vaccine compared to not receiving an XBB vaccine of any kind against COVID-19 hospitalization, emergency department or urgent care visits (ED/UC), and outpatient visits. Between September 25, 2023 and January 31, 2024, effectiveness was 24-35% during a period of JN.1 predominance and 50-61% during XBB predominance across all outcomes. VE within 60 days of vaccination during the likely JN.1 period was 32% (95% confidence interval 3-52%) against hospitalization, 41% (23-54%) against ED/UC visits, and 31% (1-52%) against outpatient visits. Corresponding VE during the likely XBB period was 62% (44-74%), 52% (37-63%), and 50% (25-66%) by setting, respectively. Here, we show the importance of strain match to maximize the public health impact of COVID-19 vaccination.

Estimates of vaccine effectiveness of the updated monovalent XBB.1.5 COVID-19 vaccine against symptomatic SARS-CoV-2 infection, hospitalization, and receipt of oxygen therapy in South Korea - October 26 to December 31, 2023

OBJECTIVES

We evaluated the vaccine effectiveness of monovalent XBB.1.5 vaccine against symptomatic COVID-19 infection, hospitalization, and the need for oxygen therapy in South Korea.

DESIGN

This study employed a test-negative case-control design. COVID-19 test results in symptomatic subjects from six university hospitals across South Korea were collected (October 26-December 31, 2023). The adjusted absolute and relative vaccine effectiveness were assessed.

RESULTS

In total, 5516 subjects were enrolled: 4,824 were unvaccinated with XBB.1.5, and 692 were vaccinated with XBB.1.5 COVID-19 mRNA vaccines. The absolute vaccine effectiveness when comparing the odds between XBB.1.5 vaccination and no vaccination against symptomatic COVID-19 infection, hospitalization, and oxygen therapy was 65.2% (95% CI, 36.1-81.0), 77.3% (95% CI, 51.1-89.5), and 85.3% (95% CI, 57.8-94.9), respectively. The relative vaccine effectiveness when comparing the odds between XBB.1.5 vaccination and no XBB.1.5 vaccination against symptomatic COVID-19 infection, hospitalization, and oxygen therapy was 57.7% (95% CI, 34.7-72.6), 64.3% (95% CI, 35.9-80.2), and 65.5% (95% CI, 27.0-83.7), respectively.

CONCLUSION

The short-term effectiveness of the XBB.1.5 vaccine against symptomatic COVID-19 infection, hospitalization, and receipt of oxygen therapy in South Korea was significant. Long-term vaccine effectiveness warrants evaluation, and these assessments should be conducted regularly.

Hajj vaccination strategies: Preparedness for risk mitigation

Millions of pilgrims travel annually to Makkah and Madinah, Saudi Arabia, for the Hajj, posing unique challenges for public health management and disease control. The large influx of pilgrims from diverse backgrounds traveling to a confined geographic area, coupled with the close proximity and interactions among them, create significant pressure on the healthcare system and heighten the potential for the spread of communicable diseases. This review examines current trends in communicable diseases and their impact, drawing insights from expert perspectives on the required (i.e., meningococcal meningitis, polio, and yellow fever) and recommended vaccinations (influenza, COVID-19) for Hajj participants. The updated COVID-19 vaccine is mandatory for local pilgrims and is strongly recommended for international visitors, with ongoing discussions on adapting protocols to address emerging variants. The timing and strain coverage of influenza vaccination, along with quadrivalent meningococcal vaccination, are also emphasized as critical preventive measures. Diseases such as cholera and yellow fever are addressed underscoring the need for rigorous surveillance and targeted vaccination strategies to mitigate the risk of transmission during the Hajj. By providing up-to-date information on mandated and recommended vaccinations, this review aims to empower pilgrims and healthcare professionals to make informed decisions regarding public health and disease prevention during this significant event.

Biases in COVID-19 vaccine effectiveness studies using cohort design

Observational studies on COVID-19 vaccine effectiveness (VE) have provided critical real-world data, informing public health policy globally. These studies, primarily using pre-existing data sources, have been indispensable in assessing VE across diverse populations and developing sustainable vaccination strategies. Cohort design is frequently employed in VE research. The rapid implementation of vaccination campaigns during the COVID-19 pandemic introduced differential vaccination influenced by sociodemographic disparities, public policies, perceived risks, health-promoting behaviors, and health status, potentially resulting in biases such as healthy user bias, healthy vaccinee effect, frailty bias, differential depletion of susceptibility bias, and confounding by indication. The overwhelming burden on healthcare systems has escalated the risk of data inaccuracies, leading to outcome misclassifications. Additionally, the extensive array of diagnostic tests used during the pandemic has also contributed to misclassification biases. The urgency to publish quickly may have further influenced these biases or led to their oversight, affecting the validity of the findings. These biases in studies vary considerably depending on the setting, data sources, and analytical methods and are likely more pronounced in low- and middle-income country (LMIC) settings due to inadequate data infrastructure. Addressing and mitigating these biases is essential for accurate VE estimates, guiding public health strategies, and sustaining public trust in vaccination programs. Transparent communication about these biases and rigorous improvement in the design of future observational studies are essential.

Public Health and Economic Impact of Periodic COVID-19 Vaccination with BNT162b2 for Old Adults and High-Risk Patients in an Illustrative Prefecture of Japan: A Budget Impact Analysis

INTRODUCTION

Japan will be transitioning from the free-of-charge COVID-19 vaccination program to annual periodic vaccination under a national immunization program for old adults and high-risk patients from 2024 fall/winter season. The policy transition including out-of-pocket payment requirement may discourage vaccination, leading to a lower vaccination rate. This study aimed to estimate the impact of varying vaccination rates with BNT162b2 COVID-19 mRNA vaccine on economics and public health in an illustrative prefecture which administers and promotes the periodic vaccination program, using budget impact analysis.

METHODS

A combined cohort Markov decision tree model estimated the public health outcomes of COVID-19-related symptomatic cases, hospitalizations and deaths; and the economic outcomes including vaccine-related cost, non-vaccine-related medical cost, and productivity loss from the societal perspective. The base case examined the impact on the outcomes when vaccination coverage changed from the reference value of 50% to upper and lower values, respectively. Scenario analyses were performed based on multiple scenarios.

RESULTS

Increase in the vaccination rate demonstrated improvement in all public health outcomes. At 50% vaccination, the vaccine-related cost for 3 years in a prefecture was estimated at JPY 7.58 billion (USD 57.67 million), the non-vaccine-related medical cost at JPY 79.22 billion (USD 602.48 million), the productivity loss at JPY 253.11 billion (USD 1.92 billion), and the total cost at JPY 339.92 billion (USD 2.59 billion). When the vaccination rate increased to 90%, the total cost decreased by JPY 4.88 billion (USD 37.11 million) (1.4%). When the vaccination rate decreased to 10%, the total cost increased by JPY 5.73 billion (USD 43.58 million) (1.7%). Results were consistent across almost all scenario analyses.

CONCLUSIONS

Maintaining a high vaccination rate with BNT162b2 is important from both public health and economic perspectives in Japan. The findings highlight to local governments the importance of continued effort to promote vaccination.

SARS-CoV-2 JN.1 variant: a short review

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a single-stranded, positive-sense RNA virus. The SARS-CoV-2 virus is evolving continuously, and many variants have been detected over the last few years. SARS-CoV-2, as an RNA virus, is more prone to mutating. The continuous evolution of the SARS-CoV-2 virus is due to genetic mutation and recombination during the genomic replication process. Recombination is a naturally occurring phenomenon in which two distinct viral lineages simultaneously infect the same cellular entity in an individual. The evolution rate depends on the rate of mutation. The rate of mutation is variable among the RNA viruses, with the SARS-CoV-2 virus exhibiting a lower rate of mutation than other RNA viruses. The novel 3'-to-5' exoribonuclease proofreading machinery is responsible for a lower rate of mutation. Infection due to the SARS-CoV-2, influenza, and respiratory syncytial virus has been reported from around the world during the same period of fall and winter, resulting in a "tripledemic." The JN.1 variant, which evolved from the predecessor, the omicron variant BA.2.86, is currently the most dominant globally. The impact of the JN.1 variant on transmissibility, disease severity, immune evasion, and diagnostic and therapeutic escape will be discussed.

Estimated Effectiveness of the BNT162b2 XBB Vaccine Against COVID-19

Importance

Data describing the early additional protection afforded by the recently recommended BNT162b2 XBB vaccine (Pfizer-BioNTech; 2023-2024 formulation) are limited.

Objective

To estimate the association between receipt of the BNT162b2 XBB vaccine and medically attended COVID-19 outcomes among US adults 18 years and older.

Design, Setting, and Participants

This test-negative case-control study was performed to estimate the effectiveness of the BNT162b2 XBB vaccine against COVID-19-associated hospitalization and emergency department (ED) or urgent care (UC) encounters among adults in the Kaiser Permanente Southern California health system between October 10, 2023, and December 10, 2023. Cases were those presenting with an acute respiratory illness and who had a positive SARS-CoV-2 polymerase chain reaction test; controls had an acute respiratory illness but tested negative for SARS-CoV-2.

Exposure

The primary exposure was receipt of the BNT162b2 XBB vaccine compared with not receiving an XBB vaccine of any kind, regardless of prior COVID-19 vaccination or SARS-CoV-2 infection history. Receipt of prior (non-XBB) versions of COVID-19 vaccines was also compared with being unvaccinated to estimate remaining protection from older vaccines.

Main Outcomes and Measures

Analyses for cases and controls were conducted separately for COVID-19 hospital admissions and ED/UC encounters. Adjusted odds ratios and 95% CIs were estimated from multivariable logistic regression models that were adjusted for patient demographic and clinical characteristics. Estimation of vaccine effectiveness was calculated as 1 - odds ratio × 100%.

Results

Among 2854 cases and 15 345 controls (median [IQR] age, 56 [37-72] years; 10 658 [58.6%] female), adjusted estimation of effectiveness of the BNT162b2 XBB vaccine received a median of 34 days prior vs not having received an XBB vaccine of any kind was 62% (95% CI, 32%-79%) against COVID-19 hospitalization and 58% (95% CI, 48%-67%) for ED/UC visits. Compared with being unvaccinated, those who had received only older versions of COVID-19 vaccines did not show statistically significant reduced risk of COVID-19 outcomes, including hospital admission.

Conclusions and Relevance

Findings of this case-control study reaffirm current recommendations for broad age-based use of annually updated COVID-19 vaccines given that (1) the BNT162b2 XBB vaccine provided statistically significant additional protection against a range of COVID-19 outcomes and (2) older versions of COVID-19 vaccines offered little, if any, long-term protection, including against hospital admission, regardless of the number or type of prior doses received.

Effectiveness of BNT162b2 XBB Vaccine Against XBB and JN.1 Sublineages

We provide updated results (11 October 2023 through 29 February 2024) from our previously conducted test-negative case-control study in Kaiser Permanente Southern California to evaluate sublineage-specific effectiveness of the BNT162b2 XBB1.5-adapted vaccine. Results suggest that XBB1.5-adapted vaccines may have reduced effectiveness against JN.1 versus XBB sublineages.

Effectiveness of COVID-19 XBB.1.5 monovalent mRNA vaccine in Korea: interim analysis

As coronavirus disease-2019 (COVID-19) becomes an endemic disease, the virus continues to evolve and become immunologically distinct from previous strains. Immune imprinting has raised concerns about bivalent mRNA vaccines containing both ancestral virus and Omicron variant. To increase efficacy against the predominant strains as of the second half of 2023, the updated vaccine formulation contained only the mRNA of XBB.1.5 sublineage. We conducted a multicenter, test-negative, case-control study to estimate XBB.1.5 monovalent vaccine effectiveness (VE) and present the results of an interim analysis with data collected in November 2023. Patients who underwent COVID-19 testing at eight university hospitals were included and matched based on age (19-49, 50-64, and ≥65 years) and sex in a 1:1 ratio. VE was calculated using the adjusted odds ratio derived from multivariable logistic regression. Of the 992 patients included, 49 (5.3%) received the XBB.1.5 monovalent vaccine at least 7 days before COVID-19 testing. Patients with COVID-19 (cases) were less likely to have received the XBB.1.5 monovalent vaccine (case 3.5% vs. control 7.2%, p=0.019) and to have a history of COVID-19 within 6 months (2.2% vs. 4.6%, p=0.068). In contrast, patients with COVID-19 were more likely to be healthcare workers (8.2% vs. 3.0%, p=0.001) and to have chronic neurological diseases (16.7% vs. 11.9%, p=0.048). The adjusted VE of the XBB.1.5 monovalent mRNA vaccine was 56.8% (95% confidence interval: 18.7-77.9%). XBB.1.5 monovalent mRNA vaccine provided significant protection against COVID-19 in the first one to two months after vaccination.

Antigenic cartography using hamster sera identifies SARS-CoV-2 JN.1 evasion seen in human XBB.1.5 booster sera

Antigenic assessments of SARS-CoV-2 variants inform decisions to update COVID-19 vaccines. Primary infection sera are often used for assessments, but such sera are rare due to population immunity from SARS-CoV-2 infections and COVID-19 vaccinations. Here, we show that neutralization titers and breadth of matched human and hamster pre-Omicron variant primary infection sera correlate well and generate similar antigenic maps. The hamster antigenic map shows modest antigenic drift among XBB sub-lineage variants, with JN.1 and BA.4/BA.5 variants within the XBB cluster, but with five to six-fold antigenic differences between these variants and XBB.1.5. Compared to sera following only ancestral or bivalent COVID-19 vaccinations, or with post-vaccination infections, XBB.1.5 booster sera had the broadest neutralization against XBB sub-lineage variants, although a five-fold titer difference was still observed between JN.1 and XBB.1.5 variants. These findings suggest that antibody coverage of antigenically divergent JN.1 could be improved with a matched vaccine antigen.

Effectiveness of Omicron XBB.1.5 vaccine against infection with SARS-CoV-2 Omicron XBB and JN.1 variants, prospective cohort study, the Netherlands, October 2023 to January 2024

We estimated vaccine effectiveness (VE) of SARS-CoV-2 Omicron XBB.1.5 vaccination against self-reported infection between 9 October 2023 and 9 January 2024 in 23,895 XBB.1.5 vaccine-eligible adults who had previously received at least one booster. VE was 41% (95% CI: 23-55) in 18-59-year-olds and 50% (95% CI: 44-56) in 60-85-year-olds. Sequencing data suggest lower protection against the BA.2.86 (including JN.1) variant from recent prior infection (OR = 2.8; 95% CI:1.2-6.5) and, not statistically significant, from XBB.1.5 vaccination (OR = 1.5; 95% CI:0.8-2.6).

Interim Effectiveness of Updated 2023-2024 (Monovalent XBB.1.5) COVID-19 Vaccines Against COVID-19-Associated Emergency Department and Urgent Care Encounters and Hospitalization Among Immunocompetent Adults Aged ≥18 Years - VISION and IVY Networks, September 2023-January 2024

In September 2023, CDC's Advisory Committee on Immunization Practices recommended updated 2023-2024 (monovalent XBB.1.5) COVID-19 vaccination for all persons aged ≥6 months to prevent COVID-19, including severe disease. However, few estimates of updated vaccine effectiveness (VE) against medically attended illness are available. This analysis evaluated VE of an updated COVID-19 vaccine dose against COVID-19-associated emergency department (ED) or urgent care (UC) encounters and hospitalization among immunocompetent adults aged ≥18 years during September 2023-January 2024 using a test-negative, case-control design with data from two CDC VE networks. VE against COVID-19-associated ED/UC encounters was 51% (95% CI = 47%-54%) during the first 7-59 days after an updated dose and 39% (95% CI = 33%-45%) during the 60-119 days after an updated dose. VE estimates against COVID-19-associated hospitalization from two CDC VE networks were 52% (95% CI = 47%-57%) and 43% (95% CI = 27%-56%), with a median interval from updated dose of 42 and 47 days, respectively. Updated COVID-19 vaccine provided increased protection against COVID-19-associated ED/UC encounters and hospitalization among immunocompetent adults. These results support CDC recommendations for updated 2023-2024 COVID-19 vaccination. All persons aged ≥6 months should receive updated 2023-2024 COVID-19 vaccine.

2023/24 mid-season influenza and Omicron XBB.1.5 vaccine effectiveness estimates from the Canadian Sentinel Practitioner Surveillance Network (SPSN)

The Canadian Sentinel Practitioner Surveillance Network reports mid-season 2023/24 influenza vaccine effectiveness (VE) of 63% (95% CI: 51-72) against influenza A(H1N1)pdm09, lower for clade 5a.2a.1 (56%; 95% CI: 33-71) than clade 5a.2a (67%; 95% CI: 48-80), and lowest against influenza A(H3N2) (40%; 95% CI: 5-61). The Omicron XBB.1.5 vaccine protected comparably well, with VE of 47% (95% CI: 21-65) against medically attended COVID-19, higher among people reporting a prior confirmed SARS-CoV-2 infection at 67% (95% CI: 28-85).

Modeling the potential public health and economic impact of different COVID-19 booster dose vaccination strategies with an adapted vaccine in the United Kingdom

BACKGROUND

Updating vaccines is essential for combatting emerging coronavirus disease 2019 (COVID-19) variants. This study assessed the public health and economic impact of a booster dose of an adapted vaccine in the United Kingdom (UK).

METHODS

A Markov-decision tree model estimated the outcomes of vaccination strategies targeting various age and risk groups in the UK. Age-specific data derived from published sources were used. The model estimated case numbers, deaths, hospitalizations, medical costs, and societal costs. Scenario analyses were conducted to explore uncertainty.

RESULTS

Vaccination targeting individuals aged ≥ 65 years and the high-risk population aged 12-64 years was estimated to avert 701,549 symptomatic cases, 5,599 deaths, 18,086 hospitalizations, 56,326 post-COVID condition cases, and 38,263 lost quality-adjusted life years (QALYs), translating into direct and societal cost savings of £112,174,054 and £542,758,682, respectively. The estimated economically justifiable price at willingness-to-pay thresholds of £20,000 and £30,000 per QALY was £43 and £61, respectively, from the payer perspective and £64 and £82, respectively, from the societal perspective. Expanding to additional age groups improved the public health impact.

CONCLUSIONS

Targeting individuals aged ≥ 65 years and those aged 12-64 years at high risk yields public health gains, but expansion to additional age groups provides additional gains.