Vaccination before or after SARS-CoV-2 infection leads to robust humoral response and antibodies that effectively neutralize variants

Development of antibody levels and subsequent decline in individuals with vaccine induced and hybrid immunity to SARS-CoV-2

OBJECTIVES

This study aimed to compare antibody trajectories among individuals with SARS-CoV-2 hybrid and vaccine-induced immunity.

METHODS

Danish adults receiving three doses of BTN162b2 or mRNA-1237 were included prior to first vaccination (Day0). SARS-CoV-2 anti-spike IgG levels were assessed before each vaccine dose, at Day90, Day180, 28 days after 3rd vaccination (Day251), Day365, and prior to 4th vaccination (Day535). SARS-CoV-2 PCR results were extracted from the national microbiology database. Mixed-effect multivariable linear regression investigated the impact of hybrid-immunity (stratified into 4 groups: no hybrid immunity, PCR+ prior to 3rd dose, PCR+ after 3rd dose and before Day365, PCR+ after Day365) on anti-spike IgG trajectories.

RESULTS

4,936 individuals were included, 47% developed hybrid-immunity. Anti-spike IgG increases were observed in all groups at Day251, with the highest levels in those PCR+ prior to 3rd dose (Geometric Mean; 535,647AU/mL vs. 374,665AU/mL with no hybrid-immunity, p=<0.0001). Further increases were observed in participants who developed hybrid immunity after their 3rd dose. Anti-spike IgG levels declined from Day 251-535 in individuals without hybrid-immunity and in those who developed hybrid-immunity prior to their 3rd dose, with lower rate of decline in those with hybrid-immunity.

CONCLUSION

Hybrid-immunity results in higher and more durable antibody trajectories in vaccinated individuals.

Altered COVID-19 immunity in children with asthma by atopic status

Background

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection causes a spectrum of clinical outcomes that may be complicated by severe asthma. Antiviral immunity is often compromised in patients with asthma; however, whether this is true for SARS-CoV-2 immunity and children is unknown.

Objective

We aimed to evaluate SARS-CoV-2 immunity in children with asthma on the basis of infection or vaccination history and compared to respiratory syncytial viral or allergen (eg, cockroach, dust mite)-specific immunity.

Methods

Fifty-three children from an urban asthma study were evaluated for medical history, lung function, and virus- or allergen-specific immunity using antibody or T-cell assays.

Results

Polyclonal antibody responses to spike were observed in most children from infection and/or vaccination history. Children with atopic asthma or high allergen-specific IgE, particularly to dust mites, exhibited reduced seroconversion, antibody magnitude, and SARS-CoV-2 virus neutralization after SARS-CoV-2 infection or vaccination. TH1 responses to SARS-CoV-2 and respiratory syncytial virus correlated with antigen-respective IgG. Cockroach-specific T-cell activation as well as IL-17A and IL-21 cytokines negatively correlated with SARS-CoV-2 antibodies and effector functions, distinct from total and dust mite IgE. Allergen-specific IgE and lack of vaccination were associated with recent health care utilization. Reduced lung function (forced expiratory volume in 1 second ≤ 80%) was independently associated with (SARS-CoV-2) peptide-induced cytokines, including IL-31, whereas poor asthma control was associated with cockroach-specific cytokine responses.

Conclusion

Mechanisms underpinning atopic and nonatopic asthma may complicate the development of memory to SARS-CoV-2 infection or vaccination and lead to a higher risk of repeated infection in these children.

From Detection to Protection: Antibodies and Their Crucial Role in Diagnosing and Combatting SARS-CoV-2

Understanding the antibody response to SARS-CoV-2, the virus responsible for COVID-19, is crucial to comprehending disease progression and the significance of vaccine and therapeutic development. The emergence of highly contagious variants poses a significant challenge to humoral immunity, underscoring the necessity of grasping the intricacies of specific antibodies. This review emphasizes the pivotal role of antibodies in shaping immune responses and their implications for diagnosing, preventing, and treating SARS-CoV-2 infection. It delves into the kinetics and characteristics of the antibody response to SARS-CoV-2 and explores current antibody-based diagnostics, discussing their strengths, clinical utility, and limitations. Furthermore, we underscore the therapeutic potential of SARS-CoV-2-specific antibodies, discussing various antibody-based therapies such as monoclonal antibodies, polyclonal antibodies, anti-cytokines, convalescent plasma, and hyperimmunoglobulin-based therapies. Moreover, we offer insights into antibody responses to SARS-CoV-2 vaccines, emphasizing the significance of neutralizing antibodies in order to confer immunity to SARS-CoV-2, along with emerging variants of concern (VOCs) and circulating Omicron subvariants. We also highlight challenges in the field, such as the risks of antibody-dependent enhancement (ADE) for SARS-CoV-2 antibodies, and shed light on the challenges associated with the original antigenic sin (OAS) effect and long COVID. Overall, this review intends to provide valuable insights, which are crucial to advancing sensitive diagnostic tools, identifying efficient antibody-based therapeutics, and developing effective vaccines to combat the evolving threat of SARS-CoV-2 variants on a global scale.

SARS-CoV-2 booster vaccine dose significantly extends humoral immune response half-life beyond the primary series

SARS-CoV-2 lipid nanoparticle mRNA vaccines continue to be administered as the predominant prophylactic measure to reduce COVID-19 disease pathogenesis. Quantifying the kinetics of the secondary immune response from subsequent doses beyond the primary series and understanding how dose-dependent immune waning kinetics vary as a function of age, sex, and various comorbidities remains an important question. We study anti-spike IgG waning kinetics in 152 individuals who received an mRNA-based primary series (first two doses) and a subset of 137 individuals who then received an mRNA-based booster dose. We find the booster dose elicits a 71-84% increase in the median Anti-S half life over that of the primary series. We find the Anti-S half life for both primary series and booster doses decreases with age. However, we stress that although chronological age continues to be a good proxy for vaccine-induced humoral waning, immunosenescence is likely not the mechanism, rather, more likely the mechanism is related to the presence of noncommunicable diseases, which also accumulate with age, that affect immune regulation. We are able to independently reproduce recent observations that those with pre-existing asthma exhibit a stronger primary series humoral response to vaccination than compared to those that do not, and further, we find this result is sustained for the booster dose. Finally, via a single-variate Kruskal-Wallis test we find no difference between male and female humoral decay kinetics, however, a multivariate approach utilizing  Least Absolute Shrinkage and Selection Operator (LASSO) regression for feature selection reveals a statistically significant (p < 1 × 10 - 3 ), albeit small, bias in favour of longer-lasting humoral immunity amongst males.

Adaptive immune responses to two-dose COVID-19 vaccine series in healthy Canadian adults ≥ 50 years: a prospective, observational cohort study

To evaluate immune responses to COVID-19 vaccines in adults aged 50 years and older, spike protein (S)-specific antibody concentration, avidity, and function (via angiotensin-converting enzyme 2 (ACE2) inhibition surrogate neutralization and antibody dependent cellular phagocytosis (ADCP)), as well as S-specific T cells were quantified via activation induced marker (AIM) assay in response to two-dose series. Eighty-four adults were vaccinated with either: mRNA/mRNA (mRNA-1273 and/or BNT162b2); ChAdOx1-S/mRNA; or ChAdOx1-S/ChAdOx1-S. Anti-S IgG concentrations, ADCP scores and ACE2 inhibiting antibody concentrations were highest at one-month post-second dose and declined by four-months post-second dose for all groups. mRNA/mRNA and ChAdOx1-S/mRNA schedules had significantly higher antibody responses than ChAdOx1-S/ChAdOx1-S. CD8+ T-cell responses one-month post-second dose were associated with increased ACE2 surrogate neutralization. Antibody avidity (total relative avidity index) did not change between one-month and four-months post-second dose and did not significantly differ between groups by four-months post-second dose. In determining COVID-19 correlates of protection, a measure that considers both antibody concentration and avidity should be considered.

Study of the cellular and humoral immune responses to SARS-CoV-2 vaccination

Our understanding of cellular immunity in response to COVID-19 infection or vaccination is limited because of less commonly used techniques. We investigated both the cellular and humoral immune responses before and after the administration of a third dose of the SARS-CoV-2 vaccine among a group of healthcare workers. Cellular immunity was evaluated using the VIDAS interferon-gamma (IFNγ) RUO test, which enables automated measurement of IFNγ levels after stimulating peripheral blood lymphocytes. Booster doses significantly enhanced both cellular and humoral immunity. Concerning cellular response, the booster dose increased the percentage of positive IFNγ release assay (IGRA) results but no difference in IFNγ release was found. The cellular response was not associated with protection against SARS-CoV-2 infection. Interestingly, vaccinated and infected healthcare workers exhibited the highest levels of anti-spike and neutralizing antibodies. In conclusion, the IGRA is a simple method for measuring cellular immune responses after vaccination. However, its usefulness as a complement to the study of humoral responses is yet to be demonstrated in future research.

High vaccination coverage and infection rate result in a robust SARS-CoV-2-specific immunity in the majority of liver cirrhosis and transplant patients: A single-center cross-sectional study

BACKGROUND

In the third year of the SARS-CoV-2 pandemic, little is known about the vaccine- and infection-induced immune response in liver transplant recipients (LTR) and liver cirrhosis patients (LCP).

OBJECTIVE

This cross-sectional study assessed the vaccination coverage, infection rate, and the resulting humoral and cellular SARS-CoV-2-specific immune responses in a cohort of LTR and LCP at the University Medical Center Hamburg-Eppendorf, Germany between March and May 2023.

METHODS

Clinical and laboratory data from 244 consecutive patients (160 LTR and 84 LCP) were collected via chart review and a patient survey. Immune responses were determined via standard spike(S)- and nucleocapsid-protein serology and a spike-specific Interferon-gamma release assay (IGRA).

RESULTS

On average, LTR and LCP were vaccinated 3.7 and 3.3 times, respectively and 59.4% of patients received ≥4 vaccinations. Altogether, 68.1% (109/160) of LTR and 70.2% (59/84) of LCP experienced a SARS-CoV-2 infection. Most infections occurred during the Omicron wave in 2022 after an average of 3.0 vaccinations. Overall, the hospitalization rate was low (<6%) in both groups. An average of 4.3 antigen contacts by vaccination and/or infection resulted in a seroconversion rate of 98.4%. However, 17.5% (28/160) of LTR and 8.3% (7/84) of LCP demonstrated only low anti-S titers (<1000 AU/ml), and 24.6% (16/65) of LTR and 20.4% (10/59) of LCP had negative or low IGRA responses. Patients with hybrid immunity (vaccination plus infection) elicited significantly higher anti-S titers compared with uninfected patients with the same number of spike antigen contacts. A total of 22.2% of patients refused additional booster vaccinations.

CONCLUSION

By spring 2023, high vaccination coverage and infection rate have resulted in a robust, mostly hybrid, humoral and cellular immune response in most LTR and LCP. However, booster vaccinations with vaccines covering new variants seem advisable, especially in patients with low immune responses and risk factors for severe disease.

Comparative single-cell transcriptomic profile of hybrid immunity induced by adenovirus vector-based COVID-19 vaccines

In this study, antibody response and a single-cell RNA-seq analysis were conducted on peripheral blood mononuclear cells from five different groups: naïve subjects vaccinated with AZD1222 (AZ) or Ad5-nCoV (Cso), individuals previously infected and later vaccinated (hybrid) with AZD1222 (AZ-hb) or Ad5-nCoV (Cso-hb), and those who were infected and had recovered from COVID-19 (Inf). The results showed that AZ induced more robust neutralizing antibody responses than Cso. The single-cell RNA data revealed a high frequency of memory B cells in the Cso and Cso-hb. In contrast, AZ and AZ-hb groups exhibited the highest proportion of activated naïve B cells expressing CXCR4. Transcriptomic analysis of CD4+ and CD8+ T cells demonstrated a heterogeneous response following vaccination, hybrid immunity, or natural infection. However, a single dose of Ad5-nCoV was sufficient to strongly activate CD4+ T cells (naïve and memory) expressing ANX1 and FOS, similar to the hybrid response observed with AZ. An interesting finding was the robust activation of a subset of CD8+ T cells expressing GZMB, GZMH, and IFNG genes in the Cso-hb group. Our findings suggest that both vaccines effectively stimulated the cellular immune response; however, the Ad5-nCoV induced a more robust CD8+ T-cell response in previously infected individuals.

Factors associated with the worsening of COVID-19 symptoms among cohorts in community- or home-isolation care in southern Thailand

Introduction

This study aimed to investigate factors associated with time-to-referral due to worsening symptoms in patients with laboratory-confirmed COVID-19 in southern Thailand. While underlying diseases have been evaluated to assess COVID-19 severity, the influence of vaccinations and treatments is also crucial.

Methods

A cohort of 8,638 patients quarantined in home or community isolation with laboratory-confirmed COVID-19 was analyzed. Survival analysis and the Cox proportional hazard ratio were employed to assess factors influencing time-toreferral.

Results

Age ≥ 60 years, neurologic disorders, cardiovascular disease, and human immunodeficiency virus infection were identified as significant risk factors for severe COVID-19 referral. Patients who received full- or booster-dose vaccinations had a lower risk of experiencing severe symptoms compared to unvaccinated patients. Notably, individuals vaccinated during the Omicron-dominant period had a substantially lower time-to-referral than those unvaccinated during the Delta-dominant period. Moreover, patients vaccinated between 1 and 6 months prior to infection had a significantly lower risk of time-to-referral than the reference group.

Discussion

These findings demonstrate early intervention in high-risk COVID-19 patients and the importance of vaccination efficacy to reduce symptom severity. The study provides valuable insights for guiding future epidemic management strategies and optimising patient care during infectious disease outbreaks.

Interim safety and immunogenicity of COVID-19 omicron BA.1 variant-containing vaccine in children in the USA: an open-label non-randomised phase 3 trial

BACKGROUND

Variant-containing mRNA vaccines for COVID-19 to broaden protection against SARS-CoV-2 variants are recommended based on findings in adults. We report interim safety and immunogenicity of an omicron BA.1 variant-containing (mRNA-1273.214) primary vaccination series and booster dose in paediatric populations.

METHODS

This open-label, two-part, non-randomised phase 3 trial enrolled participants aged 6 months to 5 years at 24 US study sites. Eligible participants were generally healthy or had stable chronic conditions, without known SARS-CoV-2 infection in the previous 90 days. Individuals who were acutely ill or febrile 1 day before or at the screening visit or those who previously received other COVID-19 vaccines (except mRNA-1273 for part 2) were excluded. In part 1, SARS-CoV-2-vaccine-naive participants received two-dose mRNA-1273.214 (25 μg; omicron BA.1 and ancestral Wuhan-Hu-1 mRNA) primary series. In part 2, participants who previously completed the two-dose mRNA-1273 (25 μg) primary series in KidCOVE (NCT04796896) received a mRNA-1273.214 (10 μg) booster dose. Primary study outcomes were safety and reactogenicity of the mRNA-1273.214 primary series (part 1) or booster dose (part 2) as well as the inferred effectiveness of mRNA-1273.214 based on immune responses against ancestral SARS-CoV-2 (D614G) and omicron BA.1 variant at 28 days post-primary series (part 1) or post-booster dose (part 2). The safety set included participants who received at least one dose of the study vaccine; the immunogenicity set included those who provided immunogenicity samples. Interim safety and immunogenicity are summarised in this analysis as of the data cutoff date (Dec 5, 2022). This trial is registered with ClinicalTrials.gov, NCT05436834.

FINDINGS

Between June 21, 2022, and Dec 5, 2022, 179 participants received one or more doses of mRNA-1273.214 primary series (part 1) and 539 received a mRNA-1273.214 booster dose (part 2). The safety profile within 28 days after either dose of the mRNA-1273.214 primary series and the booster dose was consistent with that of the mRNA-1273 primary series in this age group, with no new safety concerns or vaccine-related serious adverse events observed. At 28 days after primary series dose 2 and the booster dose, both mRNA-1273.214 primary series (day 57, including all participants with or without evidence of prior SARS-CoV-2 infection at baseline) and booster (day 29, including participants without evidence of prior SARS-CoV-2 infection at baseline) elicited responses that were superior against omicron-BA.1 (geometric mean ratio part 1: 25·4 [95% CI 20·1-32·1] and part 2: 12·5 [11·0-14·3]) and non-inferior against D614G (part 1: 0·8 [0·7-1·0] and part 2: 3·1 [2·8-3·5]), compared with neutralising antibody responses induced by the mRNA-1273 primary series (in a historical comparator group).

INTERPRETATION

mRNA-1273.214 was immunogenic against BA.1 and D614G in children aged 6 months to 5 years, with a comparable safety profile to mRNA-1273, when given as a two-dose primary series or a booster dose. These results are aligned with the US Centers for Disease Control and Prevention recommendations for the use of variant-containing vaccines for continued protection against the emerging variants of SARS-CoV-2.

FUNDING

Moderna.

Neutralizing immunity against coronaviruses in Tanzanian health care workers

The ongoing vaccination efforts and exposure to endemic and emerging coronaviruses can shape the population's immunity against this group of viruses. In this study, we investigated neutralizing immunity against endemic and emerging coronaviruses in 200 Tanzanian frontline healthcare workers (HCWs). Despite low vaccination rates (19.5%), we found a high SARS-CoV-2 seroprevalence (94.0%), indicating high exposure in these HCWs. Next, we determined the neutralization capacity of antisera against human coronavirus NL63, and 229E, SARS-CoV-1, MERS-CoV and SARS-CoV-2 (including Omicron subvariants: BA.1, BQ.1.1 and XBB.1.5) using pseudovirus neutralization assay. We observed a broad range of neutralizing activity in HCWs, but no neutralization activity detected against MERS-CoV. We also observed a strong correlation between neutralizing antibody titers for SARS-CoV-2 and SARS-CoV-1, but not between other coronaviruses. Cross-neutralization titers against the newer Omicron subvariants, BQ.1.1 and XBB.1.5, was significantly reduced compared to BA.1 and BA.2 subvariants. On the other hand, the exposed vaccinated HCWs showed relatively higher median cross-neutralization titers against both the newer Omicron subvariants and SARS-CoV-1, but did not reach statistical significance. In summary, our findings suggest a broad range of neutralizing potency against coronaviruses in Tanzanian HCWs with detectable neutralizing immunity against SARS-CoV-1 resulting from SARS-CoV-2 exposure.

SARS-CoV-2 Vaccine-Elicited Immunity after B Cell Depletion in Multiple Sclerosis

The impact of B cell deficiency on the humoral and cellular responses to SARS-CoV2 mRNA vaccination remains a challenging and significant clinical management question. We evaluated vaccine-elicited serological and cellular responses in 1) healthy individuals who were pre-exposed to SARS-CoV-2 (n = 21), 2) healthy individuals who received a homologous booster (mRNA, n = 19; or Novavax, n = 19), and 3) persons with multiple sclerosis on B cell depletion therapy (MS-αCD20) receiving mRNA homologous boosting (n = 36). Pre-exposure increased humoral and CD4 T cellular responses in immunocompetent individuals. Novavax homologous boosting induced a significantly more robust serological response than mRNA boosting. MS-α CD20 had an intact IgA mucosal response and an enhanced CD8 T cell response to mRNA boosting compared with immunocompetent individuals. This enhanced cellular response was characterized by the expansion of only effector, not memory, T cells. The enhancement of CD8 T cells in the setting of B cell depletion suggests a regulatory mechanism between B and CD8 T cell vaccine responses.

Reported effectiveness of COVID-19 monovalent booster vaccines and hybrid immunity against mild and severe Omicron disease in adults: A systematic review and meta-regression analysis

Background

Waning of COVID-19 vaccine efficacy/effectiveness (VE) has been observed across settings and epidemiological contexts. We conducted a systematic review of COVID-19 VE studies and performed a meta-regression analysis to improve understanding of determinants of waning.

Methods

Systematic review of PubMed, medRxiv and the WHO-International Vaccine Access Center database summarizing VE studies on 31 December 2022. Studies were those presenting primary adult VE data from hybrid immunity or third/fourth mRNA COVID-19 monovalent vaccine doses [due to limited data with other vaccines] against Omicron, compared with unvaccinated individuals or individuals eligible for corresponding booster doses but who did not receive them. We used meta-regression models, adjusting for confounders, with weeks since vaccination as a restricted cubic spline, to estimate VE over time since vaccination.

Results

We identified 55 eligible studies reporting 269 VE estimates. Most estimates (180/269; 67 %) described effectiveness of third dose vaccination; with 48 (18 %) and 41 (15 %) describing hybrid immunity and fourth dose effectiveness, respectively, mostly (200; 74 %) derived from test-negative design studies. Most estimates (176/269; 65 %) reported VE compared with unvaccinated comparison groups. Estimated VE against mild outcomes declined following third dose vaccination from 62 % (95 % CI: 58 % - 66 %) after 4 weeks to 48 % (41 % - 55 %) after 20 weeks. Fourth dose VE against mild COVID-19 declined from 48 % (41 % - 56 %) after 4 weeks to 47 % (19 % - 65 %) after 20 weeks. VE for severe outcomes was higher and declined in the three-dose group from 90 % (87 % - 92 %) after 4 weeks to 70 % (65 - 74 %) after 20 weeks.

Conclusions

Time-since vaccination is an important determinant of booster dose VE, a finding which may support seasonal COVID-19 booster doses. Integration of VE and immunological parameters - and longer-term data including from other vaccine types - are needed to better-understand determinants of clinical protection.

Anti SARS-CoV-2 Monoclonal Antibodies in Pre-Exposure or Post-Exposure in No- or Weak Responder to Vaccine Kidney Transplant Recipients: Is One Strategy Better than Another?

Background: Kidney transplant recipients (KTRs) are likely to develop severe COVID-19 and are less well-protected by vaccines than immunocompetent subjects. Thus, the use of neutralizing anti-SARS-CoV-2 monoclonal antibodies (mAbs) to confer a passive immunity appears attractive in KTRs. Methods: This retrospective monocentric cohort study was conducted between 1 January 2022 and 30 September 2022. All KTRs with a weak antibody response one month after three doses of mRNA vaccine (anti spike IgG < 264 (BAU/mL)) have received tixagevimab-cilgavimab in pre-exposure (group 1), post-exposure (group 2) or no specific treatment (group 3). We compared COVID-19 symptomatic hospitalizations, including intensive care unit hospitalizations, oxygen therapy, and death, between the three groups. Results: A total of 418 KTRs had SARS-CoV-2 infection in 2022. During the study period, we included 112 KTRs in group 1, 40 KTRs in group 2, and 27 KTRs in group 3. The occurrence of intensive care unit hospitalization, oxygen therapy, and COVID-19 death was significantly increased in group 3 compared to group 1 or 2. In group 3, 5 KTRs (18.5%) were admitted to the intensive care unit, 7 KTRs (25.9%) needed oxygen therapy, and 3 KTRs (11.1%) died. Patients who received tixagevimab-cilgavimab pre- or post-exposure had similar outcomes. Conclusions: This retrospective real-life study supports the relative effectiveness of tixagevimab-cilgavimab on COVID-19 infection caused by Omicron, used as a pre- or post-exposure therapy. The continued evolution of Omicron variants has made tixagevimab-cilgavimab ineffective and reinforces the need for new therapeutic monoclonal antibodies for COVID-19 active on new variants.

A semi-quantitative visual lateral flow immunoassay for SARS-CoV-2 antibody detection for the follow-up of immune response to vaccination or recovery

The lateral flow immunoassay (LFIA) technique is largely employed for the point-of-care detection of antibodies especially for revealing the immune response in serum. Visual LFIAs usually provide the qualitative yes/no detection of antibodies, while quantification requires some equipment, making the assay more expensive and complicated. To achieve visual semi-quantification, the alignment of several lines (made of the same antigen) along a LFIA strip has been proposed. The numbering of the reacting lines has been used to correlate with the quantity of some biomarkers in serum. Here, we designed the first semiquantitative LFIA for detecting antibodies and applied it to classify the immune response to SARS-CoV-2 raised by vaccination or natural infection. We used a recombinant spike receptor-binding domain (RBD) as the specific capture reagent to draw two test lines. The detection reagent was selected among three possible ligands that are able to bind to anti-spike human antibodies: the same RBD, staphylococcal protein A, and anti-human immunoglobulin G antibodies. The most convenient detector, adsorbed on gold nanoparticles, was chosen based on the highest correlation with an antibody titre of 171 human sera, measured by a reference serological method, and was the RBD (Spearman's rho = 0.84). Incorporated into the semiquantitative LFIA, it confirmed the ability to discriminate high- and low-titre samples and to classify them into two classes (Dunn's test, P < 0.05). The proposed approach enabled the semiquantification of the immune response to SARS-CoV-2 by the unaided eye observation, thus overcoming the requirement of costly and complicated equipment, and represents a general strategy for the development of semiquantitative serological LFIAs.

Diverging Maternal and Cord Antibody Functions From SARS-CoV-2 Infection and Vaccination in Pregnancy

Maternal immunity impacts the infant, but how is unclear. To understand the implications of the immune exposures of vaccination and infection in pregnancy for neonatal immunity, we evaluated antibody functions in paired peripheral maternal and cord blood. We compared those who in pregnancy received mRNA coronavirus disease 2019 (COVID-19) vaccine, were infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and the combination. We found that vaccination enriched a subset of neutralizing activities and Fc effector functions that was driven by IgG1 and was minimally impacted by antibody glycosylation in maternal blood. In paired cord blood, maternal vaccination also enhanced IgG1. However, Fc effector functions compared to neutralizing activities were preferentially transferred. Moreover, changes in IgG posttranslational glycosylation contributed more to cord than peripheral maternal blood antibody functional potency. These differences were enhanced with the combination of vaccination and infection as compared to either alone. Thus, Fc effector functions and antibody glycosylation highlight underexplored maternal opportunities to safeguard newborns.

Perspectives on SARS-CoV-2 Cases in Zoological Institutions

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in a zoological institution were initially reported in March 2020. Since then, at least 94 peer-reviewed cases have been reported in zoos worldwide. Among the affected animals, nonhuman primates, carnivores, and artiodactyls appear to be most susceptible to infection, with the Felidae family accounting for the largest number of reported cases. Clinical symptoms tend to be mild across taxa; although, certain species exhibit increased susceptibility to disease. A variety of diagnostic tools are available, allowing for initial diagnostics and for the monitoring of infectious risk. Whilst supportive therapy proves sufficient in most cases, monoclonal antibody therapy has emerged as a promising additional treatment option. Effective transmission of SARS-CoV-2 in some species raises concerns over potential spillover and the formation of reservoirs. The occurrence of SARS-CoV-2 in a variety of animal species may contribute to the emergence of variants of concern due to altered viral evolutionary constraints. Consequently, this review emphasizes the need for effective biosecurity measures and surveillance strategies to prevent and control SARS-CoV-2 infections in zoological institutions.

Enhancing Immunological Memory: Unveiling Booster Doses to Bolster Vaccine Efficacy Against Evolving SARS-CoV-2 Mutant Variants

A growing number of re-infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in previously immunized individuals has sparked discussions about the potential need for a booster vaccine dosage to counteract declining antibody levels and new strains. The protective immunity produced by vaccinations, and past illnesses relies on immunological memory. CD4 + T cells, CD8 + T cells, B cells, and long-lasting antibody responses are all components of the adaptive immune system that can generate and maintain this immunological memory. Since novel mutant variants have emerged one after the other, the world has been hit by repeated waves. Various vaccine formulations against SARS-CoV-2 have been administered across the globe. Thus, estimating the efficacy of those vaccines against gradually developed mutant stains is the essential parameter regarding the fate of those vaccine formulations and the necessity of booster doses and their frequency. In this review, focus has also been given to how vaccination stacks up against moderate and severe acute infections in terms of the longevity of the immune cells, neutralizing antibody responses, etc. However, hybrid immunity shows a greater accuracy of re-infection of variants of concern (VOCs) of SARS-CoV-2 than infection and immunization. The review conveys knowledge of detailed information about several marketed vaccines and the status of their efficacy against specific mutant strains of SARS-CoV-2. Furthermore, this review discusses the status of immunological memory after infection, mixed infection, and vaccination.

Immune response to SARS-CoV-2 variants after immunization with different vaccines in Mexico

There is limited information on the antibody responses against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in subjects from developing countries with populations having a high incidence of co-morbidities. Here, we analysed the immunogenicity of homologous schemes using the ChAdOx1-S, Sputnik V, or BNT162b2 vaccines and the effect of a booster dose with ChAdOx1-S in middle-aged adults who were seropositive or seronegative to the SARS-CoV-2 spike protein before vaccination. The study was conducted post-vaccination with a follow-up of 4 months for antibody titre using enzyme-linked immunosorbent assay (ELISA) and pseudovirus (PV) neutralization assays (PNAs). All three vaccines elicited a superior IgG anti-receptor-binding domain (RBD) and neutralization response against the Alpha and Delta variants when administered to individuals with a previous infection by SARS-CoV-2. The booster dose spiked the neutralization activity among individuals with and without a prior SARS-CoV-2 infection. The ChAdOx1-S vaccine induced weaker antibody responses in infection-naive subjects. A follow-up of 4 months post-vaccination showed a drop in antibody titre, with about 20% of the infection-naive and 100% of SARS-CoV-2 pre-exposed participants with detectable neutralization capacity against Alpha pseudovirus (Alpha-PV) and Delta PV (Delta-PV). Our observations support the use of different vaccines in a country with high seroprevalence at the vaccination time.

Longitudinal Qualitative and Quantitative Evaluation of SARS-CoV-2 Antibodies in Immunized Health Care Workers

CONTEXT.—

Many studies have depended on qualitative antibody assays to investigate questions related to COVID-19 infection, vaccination, and treatment.

OBJECTIVE.—

To evaluate immunoglobulin G (IgG) levels in vaccinated individuals over time and characterize limitations of qualitative and quantitative antibody assays.

DESIGN.—

Longitudinal serum samples (n = 339) were collected from 72 health care workers vaccinated against COVID-19. SARS-CoV-2 IgG levels before, during, and after vaccination were measured by using a qualitative anti-spike protein IgG assay and a quantitative anti-S1 IgG assay. Assay results were compared to understand antibody dynamics related to vaccination.

RESULTS.—

Qualitative testing demonstrated 100% seroconversion after the first vaccine dose, peak IgG levels after the second vaccine dose, and a progressive 50% decline during the next 8 months. Quantitative testing demonstrated that IgG levels during and after vaccination were above the analytical measurement range.

CONCLUSIONS.—

Qualitative testing demonstrates expected changes in SARS-CoV-2 IgG levels related to sequential vaccine doses and time since antigen exposure. However, proportional changes in the associated numerical signals are very likely inaccurate. Adoption of standardized quantitative SARS-CoV-2 antibody testing with a broad analytical measurement range is essential to determine a correlate of protection from COVID-19 that can be scaled for widespread use.

B-cell and antibody responses to SARS-CoV-2: infection, vaccination, and hybrid immunity

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2019 prompted scientific, medical, and biotech communities to investigate infection- and vaccine-induced immune responses in the context of this pathogen. B-cell and antibody responses are at the center of these investigations, as neutralizing antibodies (nAbs) are an important correlate of protection (COP) from infection and the primary target of SARS-CoV-2 vaccine modalities. In addition to absolute levels, nAb longevity, neutralization breadth, immunoglobulin isotype and subtype composition, and presence at mucosal sites have become important topics for scientists and health policy makers. The recent pandemic was and still is a unique setting in which to study de novo and memory B-cell (MBC) and antibody responses in the dynamic interplay of infection- and vaccine-induced immunity. It also provided an opportunity to explore new vaccine platforms, such as mRNA or adenoviral vector vaccines, in unprecedented cohort sizes. Combined with the technological advances of recent years, this situation has provided detailed mechanistic insights into the development of B-cell and antibody responses but also revealed some unexpected findings. In this review, we summarize the key findings of the last 2.5 years regarding infection- and vaccine-induced B-cell immunity, which we believe are of significant value not only in the context of SARS-CoV-2 but also for future vaccination approaches in endemic and pandemic settings.

Marine natural products and human immunity: novel biomedical resources for anti-infection of SARS-CoV-2 and related cardiovascular disease

Marine natural products (MNPs) and marine organisms include sea urchin, sea squirts or ascidians, sea cucumbers, sea snake, sponge, soft coral, marine algae, and microalgae. As vital biomedical resources for the discovery of marine drugs, bioactive molecules, and agents, these MNPs have bioactive potentials of antioxidant, anti-infection, anti-inflammatory, anticoagulant, anti-diabetic effects, cancer treatment, and improvement of human immunity. This article reviews the role of MNPs on anti-infection of coronavirus, SARS-CoV-2 and its major variants (such as Delta and Omicron) as well as tuberculosis, H. Pylori, and HIV infection, and as promising biomedical resources for infection related cardiovascular disease (irCVD), diabetes, and cancer. The anti-inflammatory mechanisms of current MNPs against SARS-CoV-2 infection are also discussed. Since the use of other chemical agents for COVID-19 treatment are associated with some adverse effects in cardiovascular system, MNPs have more therapeutic advantages. Herein, it's time to protect this ecosystem for better sustainable development in the new era of ocean economy. As huge, novel and promising biomedical resources for anti-infection of SARS-CoV-2 and irCVD, the novel potential mechanisms of MNPs may be through multiple targets and pathways regulating human immunity and inhibiting inflammation. In conclusion, MNPs are worthy of translational research for further clinical application.

Application of elastic net regression for modeling COVID-19 sociodemographic risk factors

OBJECTIVES

COVID-19 has been at the forefront of global concern since its emergence in December of 2019. Determining the social factors that drive case incidence is paramount to mitigating disease spread. We gathered data from the Social Vulnerability Index (SVI) along with Democratic voting percentage to attempt to understand which county-level sociodemographic metrics had a significant correlation with case rate for COVID-19.

METHODS

We used elastic net regression due to issues with variable collinearity and model overfitting. Our modelling framework included using the ten Health and Human Services regions as submodels for the two time periods 22 March 2020 to 15 June 2021 (prior to the Delta time period) and 15 June 2021 to 1 November 2021 (the Delta time period).

RESULTS

Statistically, elastic net improved prediction when compared to multiple regression, as almost every HHS model consistently had a lower root mean square error (RMSE) and satisfactory R2 coefficients. These analyses show that the percentage of minorities, disabled individuals, individuals living in group quarters, and individuals who voted Democratic correlated significantly with COVID-19 attack rate as determined by Variable Importance Plots (VIPs).

CONCLUSIONS

The percentage of minorities per county correlated positively with cases in the earlier time period and negatively in the later time period, which complements previous research. In contrast, higher percentages of disabled individuals per county correlated negatively in the earlier time period. Counties with an above average percentage of group quarters experienced a high attack rate early which then diminished in significance after the primary vaccine rollout. Higher Democratic voting consistently correlated negatively with cases, coinciding with previous findings regarding a partisan divide in COVID-19 cases at the county level. Our findings can assist regional policymakers in distributing resources to more vulnerable counties in future pandemics based on SVI.

Humoral immune response in people living with HIV after administration of SARS-CoV-2 vaccine CoronaVac or BNT162b2 or CoronaVac/BNT162b2 booster sequence: A cross-sectional study

BACKGROUND

The evidence of SARS-CoV-2 vaccine effectiveness in people living with HIV (PLWH) is limited. This study evaluated the humoral immune response to CoronaVac™ (virus inactivated) and BNT162b2 (mRNA- based) vaccines in PLWH and HIV-negative controls, with and without a booster sequence.

METHODS

We conducted a cross-sectional study on PLWH and HIV-negative controls who received CoronaVac or BNT162b2, with a subgroup receiving a CoronaVac/BNT162b2 booster. Blood samples were collected 4-6 months after primary vaccination and tested for anti-SARS-CoV-2 protein S (aSAb) and neutralizing antibodies (NtAb) using validated assays. Immune response was evaluated by age, sex, previous COVID-19 history, and CD4 + cell count.

FINDINGS

One hundred and eighty nine participants were enrolled with 161 (85%) being PLWH. Among participants without previous known COVID-19, median aSAb levels were significantly lower in PLWH who received CoronaVac compared to BNT162b2 (32 U/mL vs. 587 U/mL, p < 0.001), with similar results in HIV-negative controls. NtAb presence was also significantly lower after CoronaVac compared to BNT162b2 (30% vs. 93%, p < 0.001). The booster sequence group showed a significant increase in aSAb titers in both PLWH and HIV-negative controls (from 33 U/ml to 2500 U/ml, p < 0.001), and NtAb positivity increased from 20% to 95 % in PLWH, and 27% to 100% in HIV-negative controls. Prior COVID-19 led to significantly higher post-vaccine antibody titers particularly in the BNT162b2 group. PLWH with CD4 + count < 200 cells/mL showed a weaker immune response to both vaccines.

INTERPRETATION

CoronaVac resulted in a weaker immune response in both PLWH and HIV-negative controls compared to BNT162b2, particularly in immunosuppressed PLWH without prior COVID-19. Hybrid immunity and heterologous booster vaccination increased antibody levels.

FUNDING

Local funding.

Stronger and durable SARS-CoV-2 immune response to mRNA vaccines in 5-11 years old children with prior COVID-19

BACKGROUND AND OBJECTIVES

mRNA vaccines elicit a durable humoral response to SARS-CoV-2 in adults, whereas evidence in children is scarce. This study aimed to assess the early and long-term immune response to the mRNA vaccine in children with or without previous SARS-CoV-2 infection.

METHODS

In a multicentre prospective observational study, we profiled the immune response to the Pfizer BioNTech (BNT162b2) vaccine in 5-11-year-old children attending the University Pediatric Hospital of Padua and Bambino-Gesù Hospital in Rome (Italy) from December-2021 to February-2023. Blood samples were collected pre-, 1-, and 6-months after vaccination. Neutralizing antibodies (NAbs) and anti-spike-receptor-binding-domain (anti-S-RBD) IgG titers were analyzed through Plaque Reduction Neutralization Test (PRNT) and chemiluminescent immune-enzymatic assay (CLIA), respectively. Immune cell phenotypes were analyzed by flow cytometry.

RESULTS

Sixty children (26 [43 %] female, median age = 8 years [IQR = 7-10.7]) were enrolled in the study, including 46 children with a laboratory-confirmed previous COVID-19 (SARS-CoV-2-recovered) and 14 SARS-CoV-2-naïve participants defined as the absence of antigen-specific antibodies before vaccination. SARS-CoV-2-recovered participants recorded higher anti-S-RBD IgG and Wild-type and Omicron BA.2 NAbs titers than SARS-CoV-2-naïve participants at both 1- and 6-months after vaccination. Antibody titers correlated with T (Tregs) and B (Bregs) regulatory cell frequencies in SARS-CoV-2-recovered children. Both SARS-CoV-2-recovered and SARS-CoV-2-naïve participants decreased antibody titers by approximately 100 to 250 % from 1 to 6 months. While children with immunocompromising underlying conditions developed immune responses comparable to those of healthy children, solid organ transplant recipients exhibited lower levels of NAbs and anti-S-RBD IgG titers, as well as reduced frequencies of Tregs and Bregs.

CONCLUSIONS

mRNA vaccination triggered a higher production of specific anti-SARS-CoV-2 antibodies along with increased levels of regulatory cells in children with previous SARS-CoV-2 infection up to the following 6 months. These findings provide insights into boosting pre-existing immunity.

Effectiveness of BNT162b2 mRNA vaccine third doses and previous infection in protecting against SARS-CoV-2 infections during the Delta and Omicron variant waves; the UK SIREN cohort study September 2021 to February 2022

Third doses of COVID-19 vaccines were widely deployed following the primary vaccine course waning and the emergence of the Omicron-variant. We investigated protection from third-dose vaccines and previous infection against SARS-CoV-2 infection during Delta-variant and Omicron-variant (BA.1 & BA.2) waves in our frequently PCR-tested cohort of healthcare-workers. Relative effectiveness of BNT162b2 third doses and infection-acquired immunity was assessed by comparing the time to PCR-confirmed infection in boosted participants with those with waned dose-2 protection (≥254 days after dose-2), by primary series vaccination type. Follow-up time was divided by dominant circulating variant: Delta 07 September 2021 to 30 November 2021, Omicron 13 December 2021t o 28 February 2022. We used a Cox regression model with adjustment/stratification for demographic characteristics and staff-type. We explored protection associated with vaccination, infection and both. We included 19,614 participants, 29% previously infected. There were 278 primary infections (4 per 10,000 person-days of follow-up) and 85 reinfections (0.8/10,000 person-days) during the Delta period and 2467 primary infections (43/10,000 person-days) and 881 reinfections (33/10,000) during the Omicron period. Relative Vaccine Effectiveness (VE) 0-2 months post-3rd dose (3rd dose) (3-doses BNT162b2) in the previously uninfected cohort against Delta infections was 63% (95% Confidence Interval (CI) 40%-77%) and was lower (35%) against Omicron infection (95% CI 21%-47%). The relative VE of 3rd dose (heterologous BNT162b2) was greater for primary course ChAdOX1 recipients, with VE 0-2 months post-3rd dose over ≥68% higher for both variants. Third-dose protection waned rapidly against Omicron, with no significant difference between two and three BNT162b2 doses observed after 4-months. Previous infection continued to provide additional protection against Omicron (67% (CI 56%-75%) 3-6 months post-infection), but this waned to about 25% after 9-months, approximately three times lower than against Delta. Infection rates surged with Omicron emergence. Third doses of BNT162b2 vaccine provided short-term protection, with rapid waning against Omicron infections. Protection associated with infections incurred before Omicron was markedly diminished against the Omicron wave. Our findings demonstrate the complexity of an evolving pandemic with the potential emergence of immune-escape variants and the importance of continued monitoring.

Cytokine-responsive T- and NK-cells portray SARS-CoV-2 vaccine-responders and infection in multiple myeloma patients

Patients with multiple myeloma (MM) routinely receive mRNA-based vaccines to reduce COVID-19-related mortality. However, whether disease- and therapy-related alterations in immune cells and cytokine-responsiveness contribute to the observed heterogeneous vaccination responses is unclear. Thus, we analyzed peripheral blood mononuclear cells from patients with MM during and after SARS-CoV-2 vaccination and breakthrough infection (BTI) using combined whole-transcriptome and surface proteome single-cell profiling with functional serological and T-cell validation in 58 MM patients. Our results demonstrate that vaccine-responders showed a significant overrepresentation of cytotoxic CD4+ T- and mature CD38+ NK-cells expressing FAS+/TIM3+ with a robust cytokine-responsiveness, such as type-I-interferon-, IL-12- and TNF-α-mediated signaling. Patients with MM experiencing BTI developed strong serological and cellular responses and exhibited similar cytokine-responsive immune cell patterns as vaccine-responders. This study can expand our understanding of molecular and cellular patterns associated with immunization responses and may benefit the design of improved vaccination strategies in immunocompromised patients.

Applications of SARS-CoV-2 serological testing: impact of test performance, sample matrices, and patient characteristics

Laboratory testing has been a key tool in managing the SARS-CoV-2 global pandemic. While rapid antigen and PCR testing has proven useful for diagnosing acute SARS-CoV-2 infections, additional testing methods are required to understand the long-term impact of SARS-CoV-2 infections on immune response. Serological testing, a well-documented laboratory practice, measures the presence of antibodies in a sample to uncover information about host immunity. Although proposed applications of serological testing for clinical use have previously been limited, current research into SARS-CoV-2 has shown growing utility for serological methods in these settings. To name a few, serological testing has been used to identify patients with past infections and long-term active disease and to monitor vaccine efficacy. Test utility and result interpretation, however, are often complicated by factors that include poor test sensitivity early in infection, lack of immune response in some individuals, overlying infection and vaccination responses, lack of standardization of antibody titers/levels between instruments, unknown titers that confer immune protection, and large between-individual biological variation following infection or vaccination. Thus, the three major components of this review will examine (1) factors that affect serological test utility: test performance, testing matrices, seroprevalence concerns and viral variants, (2) patient factors that affect serological response: timing of sampling, age, sex, body mass index, immunosuppression and vaccination, and (3) informative applications of serological testing: identifying past infection, immune surveillance to guide health practices, and examination of protective immunity. SARS-CoV-2 serological testing should be beneficial for clinical care if it is implemented appropriately. However, as with other laboratory developed tests, use of SARS-CoV-2 serology as a testing modality warrants careful consideration of testing limitations and evaluation of its clinical utility.

Saponin Nanoparticle Adjuvants Incorporating Toll-Like Receptor Agonists Improve Vaccine Immunomodulation

Over the past few decades, the development of potent and safe immune-activating adjuvant technologies has become the heart of intensive research in the constant fight against highly mutative and immune evasive viruses such as influenza, SARS-CoV-2, and HIV. Herein, we developed a highly modular saponin-based nanoparticle platform incorporating toll-like receptor agonists (TLRas) including TLR1/2a, TLR4a, TLR7/8a adjuvants and their mixtures. These various TLRa-SNP adjuvant constructs induce unique acute cytokine and immune-signaling profiles, leading to specific Th-responses that could be of interest depending on the target disease for prevention. In a murine vaccine study, the adjuvants greatly improved the potency, durability, breadth, and neutralization of both COVID-19 and HIV vaccine candidates, suggesting the potential broad application of these adjuvant constructs to a range of different antigens. Overall, this work demonstrates a modular TLRa-SNP adjuvant platform which could improve the design of vaccines for and dramatically impact modern vaccine development.

Humoral Immune Responses following COVID-19 Vaccinations among Adults in Tanzania

COVID-19 vaccination remains to be the most important intervention in the fight against the pandemic. The immunity among the vaccinated population and its durability can significantly vary due to various factors. This study investigated the humoral immune responses among individuals who received any of the COVID-19 vaccines approved for use in Tanzania. A total of 1048 randomly selected adults who received COVID-19 vaccines at different time points were enrolled and humoral immune responses (IR) were tested at baseline and three months later (960, 91.6%). The level of SARS-CoV-2 anti-spike/receptor binding domain (RBD) IgG, anti-nucleocapsid IgG, and IgM antibodies were determined using a commercially available chemiluminescent microparticle immunoassay. Descriptive data analysis was performed using STATA version 18 and R. At baseline, serum IgG against anti-spike/RBD was detected in 1010/1048 (96.4%) participants (95%CI: 94.9-97.5) and 98.3% (95%CI: 97.3-99) three months later. The IgG against the SARS-CoV-2 nucleocapsid proteins were detected in 40.8% and 45.3% of participants at baseline and follow-up, respectively. The proportion of seroconverters following vaccination and mean titers of anti-spike/RBD antibodies were significantly more among those who had past SARS-CoV-2 infection than in those with no evidence of past infection, (p < 0.001). Only 0.5% of those who had detectable anti-spike/RBD antibodies at baseline were negative after three months of follow-up and 1.5% had breakthrough infections. The majority of participants (99.5%) had detectable anti-spike/RBD antibodies beyond 6 months post-vaccination. The proportion of Tanzanians who mounted humoral IR following COVID-19 vaccination was very high. Seroconversions, as well as the mean titers and durability of humoral IR, were significantly enhanced by exposure to natural SARS-CoV-2 infection. In view of the limited availability of COVID-19 vaccines as well as challenges to completing subsequent doses, booster doses could only be suggested to high-risk groups.

Impact of SARS-CoV-2 Infection on Humoral and Cellular Immunity in a Cohort of Vaccinated Solid Organ Transplant Recipients

The aim of the present study was to determine humoral and T-cell responses after four doses of mRNA-1273 vaccine in solid organ transplant (SOT) recipients, and to study predictors of immunogenicity, including the role of previous SARS-CoV-2 infection in immunity. Secondarily, safety was also assessed. Liver, heart, and kidney transplant recipients eligible for SARS-CoV-2 vaccination from three different institutions in Barcelona, Spain were included. IgM/IgG antibodies and T cell ELISpot against the S protein four weeks after receiving four consecutive booster doses of the vaccine were analyzed. One hundred and forty-three SOT recipients were included (41% liver, 38% heart, and 21% kidney). The median time from transplantation to vaccination was 6.6 years (SD 7.4). In total, 93% of the patients developed SARS-CoV-2 IgM/IgG antibodies and 94% S-ELISpot positivity. In total, 97% of recipients developed either humoral or cellular response (100% of liver recipients, 95% of heart recipients, and 88% of kidney recipients). Hypogammaglobulinemia was associated with the absence of SARS-CoV-2 IgG/IgM antibodies and S-ELISpot reactivity after vaccination, whereas past symptomatic SARS-CoV-2 infection was associated with SARS-CoV-2 IgG/IgM antibodies and S-ELISpot reactivity. Local and systemic side effects were generally mild or moderate, and no recipients experienced the development of de novo DSA or graft dysfunction following vaccination.

Diverging humoral and cellular immune responses due to Omicron-a national study from the Faroe Islands

IMPORTANCE

The immunity following infection and vaccination with the SARS-CoV-2 Omicron variant is poorly understood. We investigated immunity assessed with antibody and T-cell responses under different scenarios in vaccinated and unvaccinated individuals with and without Omicron infection. We found that the humoral response was higher among vaccinated-naïve than unvaccinated convalescent. Unvaccinated with and without infection had comparable low humoral responses, whereas vaccinated with a second or third dose, independent of infection status, had increasingly higher levels. Only a minor fraction of unvaccinated individuals had detectable humoral responses following Omicron infection, while almost all had positive T-cell responses. In conclusion, primary Omicron infection mounts a low humoral immune response, enhanced by prior vaccination. Omicron infection induced a robust T-cell response in both unvaccinated and vaccinated, demonstrating that immune evasion of primary Omicron infection affects humoral immunity more than T-cell immunity.

Neutralization against Omicron subvariants after BA.5/BF.7 breakthrough infection weakened as virus evolution and aging despite repeated prototype-based vaccination1

BACKGROUND

Omicron had swept the mainland China between December 2022 and January 2023, while SARS-CoV-2 still continued to evolve. To fully prepare for the next wave, it's urgent to evaluate the humoral immune response post BA.5/BF.7 breakthrough infection against predominant sub-lineages among existing vaccination strategies and the elders.

METHOD

This study enrolled a longitudinal young-adult cohort from 2/3-dose vaccination to 1 month after breakthrough infection, and an elder cohort at 1 month after breakthrough infection. Seral samples were collected and tested for humoral immune response to SARS-CoV-2 subvariants including WT, BA.2, BA.5, BF.7, BQ.1.1, CH.1.1, XBB.1.5.

RESULTS

BA.5/BF.7 breakthrough infection induced higher neutralization activity than solely vaccination in all SARS-CoV-2 strains, while the latest Omicron subvariants, BQ.1.1, CH.1.1, XBB.1.5, exhibited the strongest neutralization evasion ability. There was a negative correlation between age and humoral immune response in WT, BA.5, BQ.1.1, and XBB.1.5. Compared to non-vaccination groups, breakthrough infection in two-dose vaccination groups had significantly higher neutralizing antibody against WT, BA.2, BA.5, BF.7 but not to BQ.1.1, CH.1.1, XBB.1.5 while booster dose against the prototype prior-breakthrough would not further significantly enhance individual's humoral responses against the latest Omicron subvariants.

CONCLUSIONS

Newer variants manifest increasing immune evasion from neutralization and repeated prototype-based booster vaccines may not further enhance neutralizing antibody against emerging new variants. Older adults have lower levels of neutralizing antibody. Future vaccination strategies should aim to enhance effective neutralization to contemporary variants.

The Persistence of Specific Immunoglobulin A Against SARS-CoV-2 in Human Milk After Maternal COVID-19 Vaccination

Objectives: To investigate SARS-CoV-2 specific immunoglobulin A (sIgA) in breast milk of Thai mothers post COVID-19 vaccination and/or SARS-CoV-2 infection, and to compare the sIgA among lactating mothers with varying COVID-19 vaccination regimes. Materials and Methods: A longitudinal study was conducted in lactating mothers receiving ≥2 doses of COVID-19 vaccine or confirming SARS-CoV-2-positive test as a part of an infant feeding survey. Vaccination and infection details were collected through questionnaires and interviews. Self-collected breast milk samples (30 mL) at 1, 3, and 6 months postvaccination or infection were analyzed for sIgA through enzyme-linked immunosorbent assay (ELISA). Results: Eighty-eight lactating mothers (152 milk samples), average age of 30.7 ± 6.2 years, were recruited. Fifty-five percent of milk samples were from lactating mothers with both SARS-CoV-2 infection and vaccination (hybrid immunity); 40% were from those with vaccination alone (COVID naïve). Sixty percent of lactating mothers received mixed types of vaccines. Median sIgA ratio in breast milk was 2.67 (0.82-7.85). Breast milk sIgA at 1, 3, and 6 months were higher in mothers with hybrid immunity than in COVID naïve (geometric mean [95% confidence interval]: 3.30 [2.06-5.29] versus 1.04 [0.52-2.04], 3.39 [2.24-5.13] versus 1.26 [0.77-2.06], 4.29 [3.04-6.06] versus 1.33 [0.74-2.42], respectively). No significant differences were observed among various vaccination regimes. Conclusion: sIgA against SARS-CoV-2 was detected in breast milk for up to 6 months after immunization together with infection at a greater level than after immunization or infection alone. This immunity could be transferred and protective against SARS-CoV-2 infection. Discontinuation of breastfeeding among mothers who received COVID vaccination or experienced infection should be discouraged. Clinical Trial Registration number: TCTR20220215012.

Humoral and cellular immunity against diverse SARS-CoV-2 variants

Since the outbreak of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in late 2019, the virus has rapidly spread worldwide. This has led to an unprecedented global pandemic, marked by millions of COVID-19 cases and a significant number of fatalities. Over a relatively short period, several different vaccine platforms are developed and deployed for use globally to curb the pandemic. However, the genome of SARS-CoV-2 continuously undergoes mutation and/or recombination, resulting in the emergence of several variants of concern (VOC). These VOCs can elevate viral transmission and evade the neutralizing antibodies induced by vaccines, leading to reinfections. Understanding the impact of the SARS-CoV-2 genomic mutation on viral pathogenesis and immune escape is crucial for assessing the threat of new variants to public health. This review focuses on the emergence and pathogenesis of VOC, with particular emphasis on their evasion of neutralizing antibodies. Furthermore, the memory B cell, CD4+, and CD8+ T cell memory induced by different COVID-19 vaccines or infections are discussed, along with how these cells recognize VOC. This review summarizes the current knowledge on adaptive immunology regarding SARS-CoV-2 infection and vaccines. Such knowledge may also be applied to vaccine design for other pathogens.

Antibodies to SARS-CoV2 induced by vaccination and infection correlate with protection against the infection

The COVID-19 pandemic remained worldwide for almost three years, but little is known about the dynamics of humoral immune response to the third dose over time and its protection from infection. Our aim was to assess the humoral immune response after the third dose of the different vaccines administered to SARS-CoV-2 naive and previously infected individuals, and its correlation with protection in an academic community. For each person studied (185), three blood samples were taken between December 2021 and July 2022, one month apart. Anti-S antibodies were quantified by ELISA, while anti-N antibody levels were determined by ECLIA. Most of the participants had received two doses of viral vector-based, mRNA-based and virus-inactivated vaccines. Although anti-N antibody levels revealed that 80% of the individuals had been exposed to the virus before or during the study, only 42% reported having been diagnosed. When anti-S IgG levels were measured 3-5 months after the second dose of any vaccine, they were higher in those previously infected individuals. The same results were observed for anti-N IgG levels in those who received 2 doses of the virus-inactivated vaccine. When analyzing the dynamics of anti-S antibodies we observed that, although positive IgG antibody levels were detected 5-6 months after the second dose administration, those observed 30-60 days after the third dose were significantly higher and remained so for at least 8 months. Higher levels of anti-S IgG antibodies at the first sampling were associated with a lower incidence of subsequent infection. The same association was seen in people who received the booster compared with those who received two doses. This study provides further evidence that anti-S IgG antibodies remained at high levels over time, and both anti-S levels and the third dose of anti-SARS-CoV-2 vaccine correlate with protection against the infection. It also shows that infection acts as a booster of immunization, increasing levels of both anti-N and anti-S IgG.

Enhanced SARS-CoV-2 humoral immunity following breakthrough infection builds upon the preexisting memory B cell pool

The human immune response must continuously adapt to newly emerging SARS-CoV-2 variants. To investigate how B cells respond to repeated SARS-CoV-2 antigen exposure by Wu01 booster vaccination and Omicron breakthrough infection, we performed a molecular longitudinal analysis of the memory B cell pool. We demonstrate that a subsequent breakthrough infection substantially increases the frequency of B cells encoding SARS-CoV-2-neutralizing antibodies. However, this is not primarily attributable to maturation, but to selection of preexisting B cell clones. Moreover, broadly reactive memory B cells arose early and even neutralized highly mutated variants like XBB.1.5 that the individuals had not encountered. Together, our data show that SARS-CoV-2 immunity is largely imprinted on Wu01 over the course of multiple antigen contacts but can respond to new variants through preexisting diversity.

Population immunity predicts evolutionary trajectories of SARS-CoV-2

The large-scale evolution of the SARS-CoV-2 virus has been marked by rapid turnover of genetic clades. New variants show intrinsic changes, notably increased transmissibility, and antigenic changes that reduce cross-immunity induced by previous infections or vaccinations. How this functional variation shapes global evolution has remained unclear. Here, we establish a predictive fitness model for SARS-CoV-2 that integrates antigenic and intrinsic selection. The model is informed by tracking of time-resolved sequence data, epidemiological records, and cross-neutralization data of viral variants. Our inference shows that immune pressure, including contributions of vaccinations and previous infections, has become the dominant force driving the recent evolution of SARS-CoV-2. The fitness model can serve continued surveillance in two ways. First, it successfully predicts the short-term evolution of circulating strains and flags emerging variants likely to displace the previously predominant variant. Second, it predicts likely antigenic profiles of successful escape variants prior to their emergence.

SARS-CoV-2 specific immune responses in overweight and obese COVID-19 patients

Obesity is a known risk factor for severe respiratory tract infections. In this prospective study, we assessed the impact of being obese or overweight on longitudinal SARS-CoV-2 humoral and cellular responses up to 18 months after infection. 274 patients provided blood samples at regular time intervals up to 18 months including obese (BMI ≥30, n=32), overweight (BMI 25-29.9, n=103) and normal body weight (BMI 18.5-24.9, n=134) SARS-CoV-2 patients. We determined SARS-CoV-2 spike-specific IgG, IgA, IgM levels by ELISA and neutralising antibody titres by neutralisation assay. RBD- and spike-specific memory B cells were investigated by ELISpot, spike- and non-spike-specific IFN-γ, IL-2 and IFN-γ/IL-2 secreting T cells by FluoroSpot and T cell receptor (TCR) sequencing was performed. Higher BMI correlated with increased COVID-19 severity. Humoral and cellular responses were stronger in overweight and obese patients than normal weight patients and associated with higher spike-specific IgG binding titres relative to neutralising antibody titres. Linear regression models demonstrated that BMI, age and COVID-19 severity correlated independently with higher SARS-CoV-2 immune responses. We found an increased proportion of unique SARS-CoV-2 specific T cell clonotypes after infection in overweight and obese patients. COVID-19 vaccination boosted humoral and cellular responses irrespective of BMI, although stronger immune boosting was observed in normal weight patients. Overall, our results highlight more severe disease and an over-reactivity of the immune system in overweight and obese patients after SARS-CoV-2 infection, underscoring the importance of recognizing overweight/obese individuals as a risk group for prioritisation for COVID-19 vaccination.

Estimated Effectiveness of Coadministration of the BNT162b2 BA.4/5 COVID-19 Vaccine With Influenza Vaccine

Importance

No data comparing the estimated effectiveness of coadministering COVID-19 vaccines with seasonal influenza vaccine (SIV) in the community setting exist.

Objective

To examine the comparative effectiveness associated with coadministering the BNT162b2 BA.4/5 bivalent mRNA COVID-19 vaccine (BNT162b2-biv [Pfizer BioNTech]) and SIV vs giving each vaccine alone.

Design, Setting, and Participants

A retrospective comparative effectiveness study evaluated US adults aged 18 years or older enrolled in commercial health insurance or Medicare Advantage plans and vaccinated with BNT162b2-biv only, SIV only, or both on the same day between August 31, 2022, and January 30, 2023. Individuals with monovalent or another brand of mRNA bivalent COVID-19 vaccine were excluded.

Exposure

Same-day coadministration of BNT162b2-biv and SIV; receipt of BNT162b2-biv only (for COVID-19-related outcomes) or SIV only (for influenza-related outcomes) were the comparator groups. For adults aged 65 years or older, only enhanced SIVs were included.

Main Outcomes and Measures

COVID-19-related and influenza-related hospitalization, emergency department (ED) or urgent care (UC) encounters, and outpatient visits.

Results

Overall, 3 442 996 individuals (57.0% female; mean [SD] age, 65 [16.7] years) were included. A total of 627 735 individuals had BNT162b2-biv and SIV vaccine coadministered, 369 423 had BNT162b2-biv alone, and 2 445 838 had SIV alone. Among those aged 65 years or older (n = 2 210 493; mean [SD] age, 75 [6.7] years; 57.9% female), the coadministration group had a similar incidence of COVID-19-related hospitalization (adjusted hazard ratio [AHR], 1.04; 95% CI, 0.87-1.24) and slightly higher incidence of emergency department or urgent care encounters (AHR, 1.12; 95% CI, 1.02-1.23) and outpatient visits (AHR, 1.06; 95% CI, 1.01-1.11) compared with the BNT162b2-biv-only group. Among individuals aged 18 to 64 years (n = 1 232 503; mean [SD] age, 47 [13.1] years; 55.4% female), the incidence of COVID-19-related outcomes was slightly higher among those who received both vaccines vs BNT162b2-biv alone (AHR point estimate range, 1.14-1.57); however, fewer events overall in this age group resulted in wider CIs. Overall, compared with those who received SIV alone, the coadministration group had a slightly lower incidence of most influenza-related end points (AHR point estimates 0.83-0.93 for those aged ≥65 years vs 0.76-1.08 for those aged 18-64 years). Negative control outcomes suggested residual bias and calibration of COVID-19-related and influenza-related outcomes with negative controls moved all estimates closer to the null, with most CIs crossing 1.00.

Conclusions and Relevance

In this study, coadministration of BNT162b2-biv and SIV was associated with generally similar effectiveness in the community setting against COVID-19-related and SIV-related outcomes compared with giving each vaccine alone and may help improve uptake of both vaccines.

Respiratory mucosal immune memory to SARS-CoV-2 after infection and vaccination

Respiratory mucosal immunity induced by vaccination is vital for protection from coronavirus infection in animal models. In humans, the capacity of peripheral vaccination to generate sustained immunity in the lung mucosa, and how this is influenced by prior SARS-CoV-2 infection, is unknown. Here we show using bronchoalveolar lavage samples that donors with history of both infection and vaccination have more airway mucosal SARS-CoV-2 antibodies and memory B cells than those only vaccinated. Infection also induces populations of airway spike-specific memory CD4+ and CD8+ T cells that are not expanded by vaccination alone. Airway mucosal T cells induced by infection have a distinct hierarchy of antigen specificity compared to the periphery. Spike-specific T cells persist in the lung mucosa for 7 months after the last immunising event. Thus, peripheral vaccination alone does not appear to induce durable lung mucosal immunity against SARS-CoV-2, supporting an argument for the need for vaccines targeting the airways.

Third COVID-19 vaccine dose boosts antibody function in Rwandans with high HIV viral load

SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) causing COVID-19 (coronavirus disease 2019) poses a greater health risk to immunocompromized individuals including people living with HIV (PLWH). However, most studies on PLWH have been conducted in higher-income countries. We investigated the post-vaccination antibody responses of PLWH in Rwanda by collecting peripheral blood from participants after receiving a second or third COVID-19 vaccine. Virus-binding antibodies as well as antibody neutralization ability against all major SARS-CoV-2 variants of concern were analyzed. We found that people with high HIV viral loads and two COVID-19 vaccine doses had lower levels of binding antibodies that were less virus neutralizing and less cross-reactive compared to control groups. A third vaccination increased neutralizing antibody titers. Our data suggest that people with high HIV viral loads require a third dose of vaccine to neutralize SARS-CoV-2 virus and new variants as they emerge.

Twenty-Month Monitoring of Humoral Immune Response to BNT162b2 Vaccine: Antibody Kinetics, Breakthrough Infections, and Adverse Effects

BACKGROUND

Vaccination is one of the most effective life-saving medical interventions, and the introduction of SARS-CoV-2 vaccines was intended to prevent the serious implications of COVID-19. The objectives of the study were (i) to observe the humoral immune response to the BNT162b2 vaccine and SARS-CoV-2 infection (mainly breakthrough infections), (ii) to demonstrate the persistence of anti-SARS-CoV-2 antibodies over time in relation to the number of received vaccine doses and the course of infection, and (iii) to determine the adverse effects after primary vaccine doses.

METHODS

To assess the humoral response, IgG and IgA anti-S1 antibodies were quantified by ELISA assays. In total, the tests were carried out seven times in almost two years.

RESULTS

We demonstrated strong immunogenicity (compared to levels before primary vaccination, 150- and 20-fold increases in IgG and IgA, respectively) of the BNT162b2 vaccine. Over time, we observed a systematic decline in antibody levels, which may have contributed to breakthrough infections. Although they caused seroconversion similar to the booster, antibody levels in such patients fell more rapidly than after re-vaccination. On the other hand, in individuals who did not receive booster(s) and who did not present breakthrough infection, anti-SARS-CoV-2 antibodies returned to pre-vaccination levels after 20 months. The most commonly recognized adverse effects were injection site redness and swelling.

CONCLUSION

Vaccination is highly effective in preventing the most severe outcomes of COVID-19 and should be performed regardless of prior infection. Booster doses significantly enhance anti-SARS-CoV-2 antibody levels and, in contrast to those obtained by breakthrough infection, they remain longer.

Differential Severe Acute Respiratory Syndrome Coronavirus 2-Specific Humoral Response in Inactivated Virus-Vaccinated, Convalescent, and Breakthrough-Infected Subjects

BACKGROUND

We sought to identify potential antigens for discerning between humoral responses elicited after vaccination with CoronaVac (a severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2] inactivated vaccine), natural infection, or breakthrough infection.

METHODS

Serum samples obtained from volunteers immunized with CoronaVac (2 and 3 doses), breakthrough case patients, and from convalescent individuals were analyzed to determine the immunoglobulin (Ig) G responses against 3 structural and 8 nonstructural SARS-CoV-2 antigens.

RESULTS

Immunization with CoronaVac induced higher levels of antibodies against the viral membrane (M) protein compared with convalescent subjects both after primary vaccination and after a booster dose. Individuals receiving a booster dose displayed equivalent levels of IgG antibodies against the nucleocapsid (N) protein, similar to convalescent subjects. Breakthrough case patients produced the highest antibody levels against the N and M proteins. Antibodies against nonstructural viral proteins were present in >50% of the convalescent subjects.

CONCLUSIONS

Vaccinated individuals elicited a different humoral response compared to convalescent subjects. The analysis of particular SARS-CoV-2 antigens could be used as biomarkers for determining infection in subjects previously vaccinated with CoronaVac.

Prior vaccination promotes early activation of memory T cells and enhances immune responses during SARS-CoV-2 breakthrough infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection of vaccinated individuals is increasingly common but rarely results in severe disease, likely due to the enhanced potency and accelerated kinetics of memory immune responses. However, there have been few opportunities to rigorously study early recall responses during human viral infection. To better understand human immune memory and identify potential mediators of lasting vaccine efficacy, we used high-dimensional flow cytometry and SARS-CoV-2 antigen probes to examine immune responses in longitudinal samples from vaccinated individuals infected during the Omicron wave. These studies revealed heightened spike-specific responses during infection of vaccinated compared to unvaccinated individuals. Spike-specific cluster of differentiation (CD)4 T cells and plasmablasts expanded and CD8 T cells were robustly activated during the first week. In contrast, memory B cell activation, neutralizing antibody production and primary responses to nonspike antigens occurred during the second week. Collectively, these data demonstrate the functionality of vaccine-primed immune memory and highlight memory T cells as rapid responders during SARS-CoV-2 infection.

Omicron variant neutralizing antibodies following BNT162b2 BA.4/5 versus mRNA-1273 BA.1 bivalent vaccination in patients with end-stage kidney disease

Neutralization of Omicron subvariants by different bivalent vaccines has not been well evaluated. This study characterizes neutralization against Omicron subvariants in 98 individuals on dialysis or with a kidney transplant receiving the BNT162b2 (BA.4/BA.5) or mRNA-1273 (BA.1) bivalent COVID-19 vaccine. Neutralization against Omicron BA.1, BA.5, BQ.1.1, and XBB.1.5 increased by 8-fold one month following bivalent vaccination. In comparison to wild-type (D614G), neutralizing antibodies against Omicron-specific variants were 7.3-fold lower against BA.1, 8.3-fold lower against BA.5, 45.8-fold lower against BQ.1.1, and 48.2-fold lower against XBB.1.5. Viral neutralization was not significantly different by bivalent vaccine type for wild-type (D614G) (P = 0.48), BA.1 (P = 0.21), BA.5 (P = 0.07), BQ.1.1 (P = 0.10), nor XBB.1.5 (P = 0.10). Hybrid immunity conferred higher neutralizing antibodies against all Omicron subvariants. This study provides evidence that BNT162b2 (BA.4/BA.5) and mRNA-1273 (BA.1) induce similar neutralization against Omicron subvariants, even when antigenically divergent from the circulating variant.

Neutralizing Activity of SARS-CoV-2 Antibodies in Patients with COVID-19 and Vaccinated Individuals

BACKGROUND

Serological diagnosis of COVID-19 is complex due to the emergence of different SARS-CoV-2 variants.

METHODS

164 serum samples from (I) patients who recovered from COVID-19 (n = 62) as well as (II) vaccinated individuals (n = 52) and (III) vaccinated individuals who were infected with different SARS-CoV-2 variants after vaccination (n = 50) were included. All samples were tested using EIA (binding antibodies) and a virus neutralization test (VNT) using the Wuhan strain (NT antibodies). Group III was further tested with a VNT using the Alpha/Delta/Omicron strains.

RESULTS

The highest antibody index (AI) was observed in vaccinated individuals infected with COVID-19 (median AI = 50, IQR = 27-71) and the lowest in vaccinated individuals (median AI = 19, IQR = 8-48). Similarly, NT antibody titer was highest in vaccinated individuals infected with COVID-19 (median 128; IQR = 32-256) compared to vaccinated individuals (median 32, IQR = 4-128) and patients with COVID-19 (median 32, IQR = 8-64). The correlation between AI and NT titer was strongly positive in vaccinated individuals and moderately positive in patients with COVID-19. No significant correlation was observed in vaccinated individuals infected with COVID-19. In patients infected with Alpha and Delta, the lowest VNT positivity rate was for the Omicron variant (85.0%/83.3%). Patients infected with the Alpha variant showed the lowest NT titer for the Omicron variant (median titer 32) compared to the Wuhan/Delta variants (64/128). Patients infected with the Delta variant had the lowest NT titer to the Omicron variant (median 32), compared to the Wuhan/Alpha variants (64/128). Patients infected with the Omicron variant showed similar titers to the Delta/Wuhan variants (128) and higher to the Alpha variant (256).

CONCLUSIONS

The cross-immunity to SARS-CoV-2 is lowest for the Omicron variant compared to the Alpha/Delta variants.

Association between SARS-CoV-2 Symptoms, Ct Values, and Serological Response in Vaccinated and Unvaccinated Healthcare Personnel

BACKGROUND

SARS-CoV-2 vaccines are effective at reducing symptomatic and asymptomatic COVID-19. Limited studies have compared symptoms, threshold cycle (Ct) values from reverse transcription (RT)-PCR testing, and serological testing results between previously vaccinated vs unvaccinated populations with SARS-CoV-2 infection.

METHODS

Healthcare personnel (HCP) with a positive SARS-CoV-2 RT-PCR test within the previous 14 to 28 days completed surveys including questions about demographics, medical conditions, social factors, and symptoms of COVID-19. Ct values were observed, and serological testing was performed for anti-nucleocapsid (anti-N) and anti-Spike (anti-S) antibodies at enrollment and 40 to 90 days later. Serological results were compared to HCP with no known SARS-CoV-2 infection and negative anti-N testing.

RESULTS

There were 104 unvaccinated/not fully vaccinated and 77 vaccinated HCP with 2 doses of an mRNA vaccine at time of infection. No differences in type or duration of symptoms were reported (P = 0.45). The median (interquartile range [IQR]) Ct was 21.4 (17.6-24.6) and 21.5 (18.1-24.6) for the unvaccinated and vaccinated HCP, respectively. Higher anti-N IgG was observed in unvaccinated HCP (5.08 S/CO, 3.08-6.92) than vaccinated (3.61 signal to cutoff ratio [S/CO], 2.16-5.05). Anti-S IgG was highest among vaccinated HCP with infection (34 285 aribitrary units [AU]/mL, 17 672-61 775), followed by vaccinated HCP with no prior infection (1452 AU/mL, 791-2943), then unvaccinated HCP with infection (829 AU/mL, 290-1555). Anti-S IgG decreased 1.56% (0.9%-1.79%) per day in unvaccinated and 0.38% (0.03%-0.94%) in vaccinated HCP.

CONCLUSIONS

Vaccinated HCP infected with SARS-CoV-2 reported comparable symptoms and had similar Ct values relative to unvaccinated. However, vaccinated HCP had increased and prolonged anti-S and decreased anti-N response relative to unvaccinated.

Comparative antibody and cell-mediated immune responses, reactogenicity, and efficacy of homologous and heterologous boosting with CoronaVac and BNT162b2 (Cobovax): an open-label, randomised trial

BACKGROUND

Few trials have compared homologous and heterologous third doses of COVID-19 vaccination with inactivated vaccines and mRNA vaccines. The aim of this study was to assess immune responses, safety, and efficacy against SARS-CoV-2 infection following homologous or heterologous third-dose COVID-19 vaccination with either one dose of CoronaVac (Sinovac Biotech; inactivated vaccine) or BNT162b2 (Fosun Pharma-BioNTech; mRNA vaccine).

METHODS

This is an ongoing, randomised, allocation-concealed, open-label, comparator-controlled trial in adults aged 18 years or older enrolled from the community in Hong Kong, who had received two doses of CoronaVac or BNT162b2 at least 6 months earlier. Participants were randomly assigned, using a computer-generated sequence, in a 1:1 ratio with allocation concealment to receive a (third) dose of CoronaVac or BNT162b2 (ancestral virus strain), stratified by types of previous COVID-19 vaccination (homologous two doses of CoronaVac or BNT162b2). Participants were unmasked to group allocation after vaccination. The primary endpoint was serum neutralising antibodies against the ancestral virus at day 28 after vaccination in each group, measured as plaque reduction neutralisation test (PRNT50) geometric mean titre (GMT). Surrogate virus neutralisation test (sVNT) mean inhibition percentage and PRNT50 titres against omicron BA.1 and BA.2 subvariants were also measured. Secondary endpoints included geometric mean fold rise (GMFR) in antibody titres; incidence of solicited local and systemic adverse events; IFNγ+ CD4+ and IFNγ+ CD8+ T-cell responses at days 7 and 28; and incidence of COVID-19. Within-group comparisons of boost in immunogenicity from baseline and between-group comparisons were done according to intervention received (ie, per protocol) by paired and unpaired t test, respectively, and cumulative incidence of infection was compared using Kaplan-Meier curves and a proportional hazards model to estimate hazard ratio. The trial is registered with ClinicalTrials.gov, NCT05057169.

FINDINGS

We enrolled participants from Nov 12, 2021, to Jan 27, 2022. We vaccinated 219 participants who previously received two doses of CoronaVac, including 101 randomly assigned to receive CoronaVac (CC-C) and 118 randomly assigned to receive BNT162b2 (CC-B) as their third dose; and 232 participants who previously received two doses of BNT162b2, including 118 randomly assigned to receive CoronaVac (BB-C) and 114 randomly assigned to receive BNT162b2 (BB-B) as their third dose. The PRNT50 GMTs on day 28 against ancestral virus were 109, 905, 92, and 816; against omicron BA.1 were 9, 75, 8, and 86; and against omicron BA.2 were 6, 80, 6, and 67 in the CC-C, CC-B, BB-C, and BB-B groups, respectively. Mean sVNT inhibition percentages on day 28 against ancestral virus were 83%, 96%, 87%, and 96%; against omicron BA.1 were 15%, 58%, 19%, and 69%; and against omicron BA.2 were 43%, 85%, 50%, and 90%, in the CC-C, CC-B, BB-C, and BB-B groups, respectively. Participants who had previously received two doses of CoronaVac and a BNT162b2 third dose had a GMFR of 12 (p<0·0001) compared with those who received a CoronaVac third dose; similarly, those who had received two doses of BNT162b2 and a BNT162b2 third dose had a GMFR of 8 (p<0·0001). No differences in CD4+ and CD8+ T-cell responses were observed between groups. We did not identify any vaccination-related hospitalisation within 1 month after vaccination. We identified 58 infections when omicron BA.2 was predominantly circulating, with cumulative incidence of 15·3% and 15·4% in the CC-C and CC-B groups, respectively (p=0·93), and 16·7% and 14·0% in the BB-C and BB-B groups, respectively (p=0·56).

INTERPRETATION

Similar levels of incidence of, presumably, omicron BA.2 infections were observed in each group despite very weak antibody responses to BA.2 in the recipients of a CoronaVac third dose. Further research is warranted to identify appropriate correlates of protection for inactivated COVID-19 vaccines.

FUNDING

Health and Medical Research Fund, Hong Kong.

TRANSLATION

For the Chinese translation of the abstract see Supplementary Materials section.

Seroprevalence and indexes of IgG antibodies for SARS-CoV-2 infection among People Living With HIV, tuberculosis patients and healthcare workers, in Salvador, Brazil

INTRODUCTION

COVID-19 can trigger different clinical presentations in distinct population groups, some of which are considered at higher risk of SARS-CoV-2 infection. Little is known about the susceptibility of certain populations to the infection.

OBJECTIVES

We aimed to determine the prevalence of COVID-19 among People Living With HIV/AIDS (PLWH) attending a tertiary public hospital in Salvador, Brazil, patients with active pulmonary tuberculosis and Hospital's Healthcare Workers (HCW), and to compare their SARS-CoV-2 antibody levels.

METHODS

In this observational study we included 2294 participants from June 9, 2020 to August 10, 2021. IgG SARS-CoV-2 antibodies from all participants (275 PLWH, 42 with active tuberculosis and 1977 healthcare workers) were measured. Prevalence of COVID-19 and antibodies indexes were compared across groups.

RESULTS

We detected a higher prevalence of COVID-19 in patients with active tuberculosis (42.9%) than in PLWH (22.5%) or HCW (11.7%). Previously vaccinated participants with a COVID-19 history had median higher IgG antibody indexes (8.2; IQR: 5.5‒10) than those vaccinated who did not have COVID-19 until the time of this study (4.1; IQR: 1.6‒6.2, p < 0.001).

CONCLUSION

Prevalence of previous SARS-CoV-2 infection was higher among tuberculosis patients than that found in HCW and PLWH, but antibodies levels were similar across groups.