Binding and Neutralization Antibody Titers After a Single Vaccine Dose in Health Care Workers Previously Infected With SARS-CoV-2

Safety and efficiency of COVID-19 vaccine in North Africa

Background In the absence of a specific treatment for COVID-19, preventive measures have been implemented to control this pandemic and vaccination is one of them. However, it is crucial to verify the safety and efficiency of every vaccine. The aim was to determinate the predictive factors of side effects and reinfection after COVID-19 vaccine. Methods A cross-sectional study was conducted in February 2022 among Tunisians infected with COVID-19 between March 2020 and February 2022, using an online self-administered questionnaire. We conducted univariate and multivariate analyses using binary stepwise logistic regression. Results A total of 1541 was selected from 1911 individuals. Comorbidities affected a quarter of the population (22.3%). Before the initial infection, 39.3% had received full vaccination, and 8.7% had received partial vaccination. By February 2022, the majority (82.9%) had received at least two vaccine doses. The reinfection rate was 30.6%. All vaccines prior to the first infection was identified as a protective factor against reinfection. Inactivated virus vaccinations were less likely to induce adverse effects. Conclusion ach vaccine has its own set of advantages and disadvantages: mRNA-based vaccines had a higher incidence of side effects but all vaccines provided better protection against reinfection.

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 (Day 0). SARS-CoV-2 anti-spike IgG levels were assessed before each vaccine dose, at Day 90, Day 180, 28 days after 3rd vaccination (Day 251), Day 365, and prior to 4th vaccination (Day 535). 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 Day 365, PCR+ after Day 365) on anti-spike IgG trajectories.

RESULTS

A total of 4,936 individuals were included, 47% developed hybrid-immunity. Anti-spike IgG increases were observed in all groups at Day 251, 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.

Effects of the timing of maternal SARS-CoV-2 infection and vaccination status on placental transfer of antibodies to neonates: A cross-sectional study

OBJECTIVES

To assess the effects of timing of maternal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and vaccination status on placental transfer of antibodies to neonates.

METHODS

In this cross-sectional study, chemiluminescence was employed to measure SARS-CoV-2 IgG antibody titers in paired maternal-infant samples from women infected during pregnancy who were vaccinated or unvaccinated. Generalized linear regression assessed factors affecting antibody transfer in infected pregnant women and neonatal titers.

RESULTS

The group with ≥90 days between infection and delivery showed a higher antibody transfer rate than the <90 days group (β= 0.33, 95%CI: 0.01-0.65). Neonatal IgG titers correlated significantly with maternal titers and with maternal infections more than 90 days before delivery. Among infected pregnant women, those who had received 2 or 3 doses of vaccine before pregnancy had higher neonatal antibody titers than those who were not vaccinated (β = 57.70, 95%CI: 31.33-84.07).

CONCLUSION

Neonates born to pregnant women who were vaccinated before infection showed higher antibody titers than neonates of pregnant women who were not vaccinated before infection. The transfer rate is higher in pregnant women with ≥90 days from infection to delivery than in those with <90 days. These findings highlight the importance of timely maternal vaccination to optimize maternal and infant immunity.

Hybrid immunity after BNT162b2 Covid-19 vaccine administration in children aged 5 to 11 years

BACKGROUND

The immune response to coronavirus disease 2019 (COVID-19) vaccination is stronger among adults with prior infection (hybrid immunity). It is important to understand if children demonstrate a similar response to better inform vaccination strategies. Our study investigated the humoral response after BNT162b2 COVID-19 vaccine doses in SARS-CoV-2 naïve and recovered children (5-11 years).

METHODS

A multi-institutional, longitudinal, prospective cohort study was conducted. Children were enrolled in a case-ascertained antibody surveillance study in Ottawa, Ontario from September/2020-March/2021; at least one household member was severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) positive on RT-PCR. In November 2021, BNT162b2 COVID-19 vaccine was authorized for children aged 5-11 in Canada. Children enrolled in the surveillance study intending to receive two vaccine doses were invited to participate in this study from November 2021-April 2022. Main exposure was prior SARS-CoV-2 infection, defined by positive RT-PCR or SARS-CoV-2 anti-N IgG antibody presence. Primary outcome was spike IgG antibody levels measured following the first vaccine dose (2-3 weeks) and second vaccine dose (3-4 weeks).

RESULTS

Of the 153 eligible children, 75 participants (median age 8.9 IQR (7.4, 10.2) years; 38 (50.7 %) female; 59 (78.7 %) Caucasian) had complete follow-up. Fifty-four (72 %) children had prior SARS-COV-2 infection. Spike IgG antibody levels are significantly higher in SARS-CoV-2 recovered participants after receiving the first dose (p < 0.001) and the second (p = 0.01) compared to infection naïve children.

CONCLUSIONS AND RELEVANCE

SARS-CoV-2 recovered children (5-11 years) demonstrated higher antibody levels following first BNT162b2 vaccine dose compared with naïve children. Most reached antibody saturation two to three weeks after the first dose; a second dose didn't change the saturation level. A single vaccine dose in SARS-CoV-2 recovered children may be equivalent or superior to a 2-dose primary series in naïve children. Further research is needed on the durability and quality of a single vaccine dose in this population.

Host-microbe multiomic profiling reveals age-dependent immune dysregulation associated with COVID-19 immunopathology

Age is a major risk factor for severe coronavirus disease 2019 (COVID-19), yet the mechanisms behind this relationship have remained incompletely understood. To address this, we evaluated the impact of aging on host immune response in the blood and the upper airway, as well as the nasal microbiome in a prospective, multicenter cohort of 1031 vaccine-naïve patients hospitalized for COVID-19 between 18 and 96 years old. We performed mass cytometry, serum protein profiling, anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody assays, and blood and nasal transcriptomics. We found that older age correlated with increased SARS-CoV-2 viral abundance upon hospital admission, delayed viral clearance, and increased type I interferon gene expression in both the blood and upper airway. We also observed age-dependent up-regulation of innate immune signaling pathways and down-regulation of adaptive immune signaling pathways. Older adults had lower naïve T and B cell populations and higher monocyte populations. Over time, older adults demonstrated a sustained induction of pro-inflammatory genes and serum chemokines compared with younger individuals, suggesting an age-dependent impairment in inflammation resolution. Transcriptional and protein biomarkers of disease severity differed with age, with the oldest adults exhibiting greater expression of pro-inflammatory genes and proteins in severe disease. Together, our study finds that aging is associated with impaired viral clearance, dysregulated immune signaling, and persistent and potentially pathologic activation of pro-inflammatory genes and proteins.

Self-reported side effects of COVID-19 vaccines among the public

Background

The safety, side effects and efficacy profile of COVID-19 vaccines remain subjects of ongoing concern among the public in Malaysia. The aim of this study was to determine the types of adverse effects following immunisation with COVID-19 vaccines and the differences based on various types of COVID-19 vaccines to raise public awareness and reduce vaccine hesitancy among the public.

Methods

A total of 901 Malaysian adults (≥18 years) who received various COVID-19 vaccines were selected to participate in our cross-sectional study through an online survey between December 2021 and January 2022.

Results

A total of 814 (90.3%) of the participants reported ≥1 side effect following COVID-19 immunisation. Of these, the predominant symptoms were swelling at the injection site (n = 752, 83.5%), headache (n = 638, 70.8%), pain or soreness at the injection site (n = 628, 69.7%), fatigue or tiredness (n = 544, 60.4%), muscle weakness (n = 529, 58.7%) and diarrhea (n = 451, 50.1%). Recipients of the Pfizer-BioNTech (Comirnaty ®) vaccine reported the highest number of adverse effects (n = 355, 43.6%), followed by mixed COVID-19 vaccines (n = 254, 31.2%), the Oxford-AstraZeneca (ChAdOx1-®[recombinant]) vaccine (n = 113, 13.9%) and the Sinovac (CoronaVac®) vaccine (n = 90, 11.1%). The study showed that individuals who reported significantly more side effects were of elderly age, female gender and high educational level [P value < 0.05]. Mixed COVID-19 vaccine recipients also reported significantly more local and systemic symptoms after the first dose and third dose when compared with other single vaccine recipients.

Conclusion

This study demonstrated the types of self-reported adverse effects following immunisation with single and mixed COVID-19 vaccines. These findings may provide the side effects of different COVID-19 vaccines with the hope of educating the public on the safety profiles of these vaccines and reducing vaccine hesitancy among the public.

Performance of Three Anti-SARS-CoV-2 Anti-S and One Anti-N Immunoassays for the Monitoring of Immune Status and Vaccine Response

This study aimed to evaluate and compare the performance of three anti-S and one anti-N assays that were available to the project in detecting antibody levels after three commonly used SARS-CoV-2 vaccines (Pfizer, Moderna, and Johnson & Johnson). It also aimed to assess the association of age, sex, race, ethnicity, vaccine timing, and vaccine side effects on antibody levels in a cohort of 827 individuals. In September 2021, 698 vaccinated individuals donated blood samples as part of the Association for Diagnostics & Laboratory Medicine (ADLM) COVID-19 Immunity Study. These individuals also participated in a comprehensive survey covering demographic information, vaccination status, and associated side effects. Additionally, 305 age- and gender-matched samples were obtained from the ADLM 2015 sample bank as pre-COVID-19-negative samples. All these samples underwent antibody level analysis using three anti-S assays, namely Beckman Access SARS-CoV-2 IgG (Beckman assay), Ortho Clinical Diagnostics VITROS Anti-SARS-CoV-2 IgG (Ortho assay), Siemens ADVIA Centaur SARS-CoV-2 IgG (Siemens assay), and one anti-N antibody assay: Bio-Rad Platelia SARS-CoV-2 Total Ab assay (BioRad assay). A total of 827 samples (580 COVID-19 samples and 247 pre-COVID-19 samples) received results for all four assays and underwent further analysis. Beckman, Ortho, and Siemens anti-S assays showed an overall sensitivity of 99.5%, 97.6%, and 96.9%, and specificity of 90%, 100%, and 99.6%, respectively. All three assays indicated 100% sensitivity for individuals who received the Moderna vaccine and boosters, and over 99% sensitivity for the Pfizer vaccine. Sensitivities varied from 70.4% (Siemens), 81.5% (Ortho), and 96.3% (Beckman) for individuals who received the Johnson & Johnson vaccine. BioRad anti-N assays demonstrated 46.2% sensitivity and 99.25% specificity based on results from individuals with self-reported infection. The highest median anti-S antibody levels were measured in individuals who received the Moderna vaccine, followed by Pfizer and then Johnson & Johnson vaccines. Higher anti-S antibody levels were significantly associated with younger age and closer proximity to the last vaccine dose but were not associated with gender, race, or ethnicity. Participants with higher anti-S levels experienced significantly more side effects as well as more severe side effects (e.g., muscle pain, chills, fever, and moderate limitations) (p < 0.05). Anti-N antibody levels only indicated a significant correlation with headache. This study indicated performance variations among different anti-S assays, both among themselves and when analyzing individuals with different SARS-CoV-2 vaccines. Caution should be exercised when conducting large-scale studies to ensure that the same platform and/or assays are used for the most effective interpretation of the data.

Microfluidic-assisted single-cell RNA sequencing facilitates the development of neutralizing monoclonal antibodies against SARS-CoV-2

As a class of antibodies that specifically bind to a virus and block its entry, neutralizing monoclonal antibodies (neutralizing mAbs) have been recognized as a top choice for combating COVID-19 due to their high specificity and efficacy in treating serious infections. Although conventional approaches for neutralizing mAb development have been optimized for decades, there is an urgent need for workflows with higher efficiency due to time-sensitive concerns, including the high mutation rate of SARS-CoV-2. One promising approach is the identification of neutralizing mAb candidates via single-cell RNA sequencing (RNA-seq), as each B cell has a unique transcript sequence corresponding to its secreted antibody. The state-of-the-art high-throughput single-cell sequencing technologies, which have been greatly facilitated by advances in microfluidics, have greatly accelerated the process of neutralizing mAb development. Here, we provide an overview of the general procedures for high-throughput single-cell RNA-seq enabled by breakthroughs in droplet microfluidics, introduce revolutionary approaches that combine single-cell RNA-seq to facilitate the development of neutralizing mAbs against SARS-CoV-2, and outline future steps that need to be taken to further improve development strategies for effective treatments against infectious diseases.

Host-Microbe Multiomic Profiling Reveals Age-Dependent COVID-19 Immunopathology

Age is a major risk factor for severe coronavirus disease-2019 (COVID-19), yet the mechanisms responsible for this relationship have remained incompletely understood. To address this, we evaluated the impact of aging on host and viral dynamics in a prospective, multicenter cohort of 1,031 patients hospitalized for COVID-19, ranging from 18 to 96 years of age. We performed blood transcriptomics and nasal metatranscriptomics, and measured peripheral blood immune cell populations, inflammatory protein expression, anti-SARS-CoV-2 antibodies, and anti-interferon (IFN) autoantibodies. We found that older age correlated with an increased SARS-CoV-2 viral load at the time of admission, and with delayed viral clearance over 28 days. This contributed to an age-dependent increase in type I IFN gene expression in both the respiratory tract and blood. We also observed age-dependent transcriptional increases in peripheral blood IFN-γ, neutrophil degranulation, and Toll like receptor (TLR) signaling pathways, and decreases in T cell receptor (TCR) and B cell receptor signaling pathways. Over time, older adults exhibited a remarkably sustained induction of proinflammatory genes (e.g., CXCL6) and serum chemokines (e.g., CXCL9) compared to younger individuals, highlighting a striking age-dependent impairment in inflammation resolution. Augmented inflammatory signaling also involved the upper airway, where aging was associated with upregulation of TLR, IL17, type I IFN and IL1 pathways, and downregulation TCR and PD-1 signaling pathways. Metatranscriptomics revealed that the oldest adults exhibited disproportionate reactivation of herpes simplex virus and cytomegalovirus in the upper airway following hospitalization. Mass cytometry demonstrated that aging correlated with reduced naïve T and B cell populations, and increased monocytes and exhausted natural killer cells. Transcriptional and protein biomarkers of disease severity markedly differed with age, with the oldest adults exhibiting greater expression of TLR and inflammasome signaling genes, as well as proinflammatory proteins (e.g., IL6, CXCL8), in severe COVID-19 compared to mild/moderate disease. Anti-IFN autoantibody prevalence correlated with both age and disease severity. Taken together, this work profiles both host and microbe in the blood and airway to provide fresh insights into aging-related immune changes in a large cohort of vaccine-naïve COVID-19 patients. We observed age-dependent immune dysregulation at the transcriptional, protein and cellular levels, manifesting in an imbalance of inflammatory responses over the course of hospitalization, and suggesting potential new therapeutic targets.

Long-Term Dynamic Changes in Hybrid Immunity over Six Months after Inactivated and Adenoviral Vector Vaccination in Individuals with Previous SARS-CoV-2 Infection

Numerous studies have largely focused on short-term immunogenicity in recovered individuals post mRNA vaccination. However, understanding the long-term durability, particularly in inactivated and adenoviral vectored vaccines, remains limited. We evaluated antibody responses, omicron variant neutralization, and IFN-γ responses in 119 previously infected individuals vaccinated with CoronaVac or ChAdOx1 up to six months post-vaccination. Both vaccines elicited robust immune responses in recovered individuals, surpassing those who were infection-naïve, and these persisted above pre-vaccination levels for six months. However, antibody levels declined over time (geometric mean ratio (GMR) = 0.52 for both vaccines). Notably, neutralizing activities against omicron declined faster in ChAdOx1 (GMR = 0.6) compared to CoronaVac recipients (GMR = 1.03). While the first dose of ChAdOx1 adequately induced immune responses in recovered individuals, a second dose demonstrated advantages in omicron variant neutralization and slower decline. Although both vaccines induced T cell responses, the median IFN-γ level at six months returned to pre-vaccination levels. However, more individuals exhibited reactive T cell responses. Extending the interval (13-15 months) between infection and vaccination could enhance antibody levels and broaden neutralization. Together, these findings demonstrate a robust humoral and cellular response that was sustained for at least six months after vaccination, thus guiding optimal vaccination strategies based on prior infection and vaccine platforms.

Magnitude and Durability of the Antibody Response to mRNA-Based Vaccination Among SARS-CoV-2 Seronegative and Seropositive Health Care Personnel

Few studies have described changes in SARS-CoV-2 antibody levels in response to infection and vaccination at frequent intervals and over extended follow-up periods. The purpose of this study was to assess changes in SARS-CoV-2-specific antibody responses among a prospective cohort of health care personnel over 18 months with up to 22 samples per person. Antibody levels and live virus neutralization were measured before and after mRNA-based vaccination with results stratified by (1) SARS-CoV-2 infection status prior to initial vaccination and (2) SARS-CoV-2 infection at any point during follow-up. We found that the antibody response to the first dose was almost 2-fold higher in individuals who were seropositive prior to vaccination, although neutralization titers were more variable. The antibody response induced by vaccination appeared to wane over time but generally persisted for 8 to 9 months, and those who were infected at any point during the study had slightly higher antibody levels over time vs those who remained uninfected. These findings underscore the need to account for SARS-CoV-2 natural infection as a modifier of vaccine responses, and they highlight the importance of frequent testing of longitudinal antibody titers over time. Together, our results provide a clearer understanding of the trajectories of antibody response among vaccinated individuals with and without prior SARS-CoV-2 infection.

The Healthcare Study Examines the Humoral Anti-S1 Antibody Response Following mRNA Vaccination, Comparing Individuals with and without Prior SARS-CoV-2 Infection

Vaccines targeting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been pivotal in curtailing the spread of infection. Health care workers, as frontline responders, were among the first to receive vaccination to mitigate coronavirus disease in 2019 (COVID-19) transmission. This study aimed to assess the humoral response elicited by mRNA vaccines, specifically measuring antibodies against the spike S1 protein, a marker of immune response. A cohort of 649 health care workers received three doses of mRNA vaccine, with antibody levels evaluated before and after each dose within a 2- to 3-week interval. Participants were stratified into groups based on prior exposure to the virus: those without prior contact (440 individuals) and those with a history of infection (209 individuals). Among the latter, cases of SARS-CoV-2 infection ranged from asymptomatic (92 individuals) to mild symptomatic (117 individuals). Participants with a history of infection exhibited elevated levels of IgG antibodies against the S1 protein prior to vaccination. Notably, both immunoglobulin IgA class (IgA) and immunoglobulin IgG class (IgG) antibody responses increased significantly post-vaccination, peaking after the second dose for IgG and after the third dose for IgA. Interestingly, the immune response to the vaccine did not vary significantly based on the symptomatic or asymptomatic nature of prior infection. Furthermore, the study findings indicate that completion of the vaccination regimen led to sustained antibody production lasting between 6 months and 9 months. This study underscores the robust and enduring humoral response elicited by mRNA vaccines, particularly among health care workers, irrespective of prior SARS-CoV-2 exposure.

Anti-S Antibodies Against SARS-CoV-2 Infection Among Four Types of Vaccines in Malaysia

Monitoring SARS-CoV-2 antibody levels can provide insights into a person's immunity to COVID-19 and inform decisions about vaccination and public health measures. Anti-S may be useful as an indicator of an effective immune response. Thus, we conducted this study that aimed to determine the immune response of anti-S antibodies against SARS-CoV-2 for all the vaccine types over time among adult recipients in Malaysia and to determine the associated factors. This study was a cohort that recruited 2513 respondents aged 18 years and above from June to December 2021. Each participant was followed-up for 1-year period from the initial vaccine dose (baseline). We found that the anti-S antibody generally increased for all vaccine types and peaked at two weeks after the second dose vaccination, with Pfizer recipients having the highest median of 100 (100.00-100.00). During the third-month follow-up, the seropositivity of anti-S antibody and the median level decreased for all vaccines. We found that type of vaccines, comorbid status, infection, and booster status were significantly associated with the anti-S antibody level after one year.

What can neutralizing antibodies tell us about the quality of immunity in COVID-19 convalescents and vaccinees?

During the SARS-CoV-2 pandemic, the lack of standardized measurements of the immune response after vaccination or recovery from COVID-19 resulted in incomparable results and hindered correlation establishment. Prioritizing reliable and standardized methods to monitor pathogen-specific immunity is crucial, not only during the COVID-19 pandemic but also for future outbreaks. During our study of the humoral immune response, we used a SARS-CoV-2 wild-type neutralization assay, ensuring the measurement of the immune response directed to all SARS-CoV-2 antigens in their proper conformation. A head-to-head comparison of the neutralizing antibody (NAb) responses elicited by four vaccines used in Europe during 2021 (BNT162b2, mRNA-1273, ChAdOx nCoV-19, and Ad26.COV2.S) and their comparison to NAb responses in convalescents showed that while the amount was comparable, NAbs induced by natural infection were of higher quality. Namely, NAbs produced by disease were better activators of the complement system than NAbs induced by vaccination. Furthermore, the contribution of spike protein-specific IgGs to the SARS-CoV-2 neutralization was lower in convalescents compared to vaccinees, indicating that those who recovered from COVID-19 were armed with antibodies of additional specificities and/or classes that contributed to virus neutralization. These findings suggest that a higher stringency of public policy measures targeting individuals who have recovered from COVID-19, in comparison to those who have been vaccinated, may not have been fully justified.

Immune responses of lung transplant recipients against SARS-CoV-2 and common respiratory coronaviruses: Evidence for pre-existing cross-reactive immunity

Humoral and cellular immune responses to SARS-CoV-2 and other coronaviruses in lung transplant recipients are unknown. We measured antibodies and T cell responses against the SARS-CoV-2 spike S2 and nucleocapsid antigens and spike antigens from common respiratory coronaviruses (229E, NL63, OC43, and HKU1) after vaccination or infection of LTxRs. 148 LTxRs from single center were included in this study: 98 after vaccination and 50 following SARS-CoV-2 infection. Antibodies were quantified by enzyme-linked immunosorbent assay. The frequency of T cells secreting IL2, IL4, IL10, IL17, TNFα, and IFNγ were enumerated by enzyme-linked immunospot assay. Our results have shown the development of antibodies to SARS-CoV-2 spike protein in infected LTxRs (39/50) and vaccinated LTxRs (52/98). Vaccinated LTxRs had higher number of T cells producing TNFα but less cells producing IFNγ than infected LTxRs in response to the nucleocapsid antigen and other coronavirus spike antigens. We didn't find correlation between the development of antibodies and cellular immune responses against the SARS-CoV-2 spike protein after vaccination. Instead, LTxRs have pre-existing cellular immunity to common respiratory coronaviruses, leading to cross-reactive immunity against SARS-CoV-2 which likely will provide protection against SARS-Cov-2 infection.

Comparison of Antibody Responses After CoronaVac and BNT162b2 Vaccines in Healthcare Workers

Since the initial outbreak in late December 2019, the coronavirus disease 2019 (COVID-19) pandemic has become a significant healthcare issue worldwide. Despite patients getting the total recommended doses of the COVID-19 vaccine, it is still unable to stop the spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Our study aimed to evaluate the antibody response in the 3rd month after two doses of the CoronaVac vaccine and after a single dose of the BNT162b2 vaccine. One hundred thirty-five people from Tarsus State Hospital health workers were included in the study. We collected serum samples from healthcare workers 3 months post-vaccination, and the Anti-SARS-CoV-2 Quanti-Vac ELISA IgG kit coated with recombinant S1 antigen was used to test for SARS-CoV-2 antibodies. Antibody levels of BNT162b2 (last vaccine) patients are significantly higher than CoronaVac ones (p < 0.05). It was determined that those who do not have a concomitant disease and those who do not smoke have higher antibody levels after CoronaVac than the others (p < 0.05). It was determined that 53.1% of 32 patients with pain, swelling, redness at the vaccination site after CoronaVac did not have pain/swelling/redness at the vaccination site after BNT162b2 (p < 0.05). Headache was also more common after CoronaVac compared to the BNT162b2 vaccine (p < 0.05). In conclusion, IgG seropositivity was lower after CoronaVac than BNT162b2, and the antibody level for CoronaVac recipients has decreased over time since vaccination, but not for BNT162b2 recipients.

Infection pre-Ad26.COV2.S-vaccination primes greater class switching and reduced CXCR5 expression by SARS-CoV-2-specific memory B cells

Neutralizing antibodies strongly correlate with protection for COVID-19 vaccines, but the corresponding memory B cells that form to protect against future infection are relatively understudied. Here we examine the effect of prior SARS-CoV-2 infection on the magnitude and phenotype of the memory B cell response to single dose Johnson and Johnson (Ad26.COV2.S) vaccination in South African health care workers. Participants were either naïve to SARS-CoV-2 or had been infected before vaccination. SARS-CoV-2-specific memory B-cells expand in response to Ad26.COV2.S and are maintained for the study duration (84 days) in all individuals. However, prior infection is associated with a greater frequency of these cells, a significant reduction in expression of the germinal center chemokine receptor CXCR5, and increased class switching. These B cell features correlated with neutralization and antibody-dependent cytotoxicity (ADCC) activity, and with the frequency of SARS-CoV-2 specific circulating T follicular helper cells (cTfh). Vaccination-induced effective neutralization of the D614G variant in both infected and naïve participants but boosted neutralizing antibodies against the Beta and Omicron variants only in participants with prior infection. In addition, the SARS-CoV-2 specific CD8+ T cell response correlated with increased memory B cell expression of the lung-homing receptor CXCR3, which was sustained in the previously infected group. Finally, although vaccination achieved equivalent B cell activation regardless of infection history, it was negatively impacted by age. These data show that phenotyping the response to vaccination can provide insight into the impact of prior infection on memory B cell homing, CSM, cTfh, and neutralization activity. These data can provide early signals to inform studies of vaccine boosting, durability, and co-morbidities.

Antibody Response against Severe Acute Respiratory Syndrome Coronavirus 2 Messenger Ribonucleic Acid Vaccines in Infected Individuals: A Systematic Review

Individuals with a history of coronavirus disease 2019 (COVID-19) exhibit memory immunity acquired during natural infection. However, a decline in immunity after infection renders these individuals vulnerable to re-infection, in addition to a higher risk of infection with new variants. This systematic review examined related studies to elucidate the antibody response in these infected individuals after messenger ribonucleic acid (mRNA) vaccination. Hence, the focus of this review was to ascertain differences in the concentration of binding and neutralising antibodies of previously infected individuals in comparison to those of infection-naïve individuals after administration of two doses of mRNA vaccination through available case-control and cohort studies. Positive reverse transcriptase-polymerase chain reaction (RT-PCR) test or detectable anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies at the baseline in included studies showed categorisation of infected and uninfected individuals. This review utilised three online databases: PubMed, Scopus and Cochrane with the following keywords: (COVID-19 OR 'Coronavirus Disease 2019' OR SARS-CoV-2) AND Immun* AND (Pfizer OR BioNTech OR BNT162b2 OR Comirnaty OR Moderna OR mRNA-1273) from January 2019 to July 2021. Following the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocol (PRISMA-P) 2020 guidelines and assessment based on the Crowe Critical Appraisal Tool (CCAT), we included 13 related qualified papers of observational studies discerning the binding and neutralising antibody concentrations of infected and uninfected individuals after administration of mRNA vaccines, such as the BNT162b2 and mRNA-1273 vaccine. The mRNA vaccines induced robust binding and neutralising antibody responses in both groups. However, infected individuals showed induction of higher antibody responses in a shorter time compared to uninfected individuals. Hence, a single dose of mRNA vaccination for infected individuals may be sufficient to reach the same level of antibody concentration as that observed in uninfected individuals after receiving two doses of vaccination.

T-cell immunity to SARS-CoV-2: what if the known best is not the optimal course for the long run? Adapting to evolving targets

Humanity did surprisingly well so far, considering how unprepared it was to respond to the coronavirus disease 2019 (COVID-19) threat. By blending old and ingenious new technology in the context of the accumulated knowledge on other human coronaviruses, several vaccine candidates were produced and tested in clinical trials in record time. Today, five vaccines account for the bulk of the more than 13 billion doses administered worldwide. The ability to elicit biding and neutralizing antibodies most often against the spike protein is a major component of the protection conferred by immunization but alone it is not enough to limit virus transmission. Thus, the surge in numbers of infected individuals by newer variants of concern (VOCs) was not accompanied by a proportional increase in severe disease and death rate. This is likely due to antiviral T-cell responses, whose evasion is more difficult to achieve. The present review helps navigating the very large literature on T cell immunity induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and vaccination. We examine the successes and shortcomings of the vaccinal protection in the light of the emergence of VOCs with breakthrough potential. SARS-CoV-2 and human beings will likely coexist for a long while: it will be necessary to update existing vaccines to improve T-cell responses and attain better protection against COVID-19.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Antibody Titer Levels in Pregnant Individuals After Infection, Vaccination, or Both

We examined differences in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody responses in pregnant individuals with natural, vaccine-induced, or combined immunity. Participants had live or nonlive births between 2020 and 2022, were seropositive (SARS-CoV-2 spike protein, anti-S), and had available mRNA vaccination and infection information (n=260). We compared titer levels among three immunity profiles: 1) natural immunity (n=191), 2) vaccine-induced immunity (n=37), and 3) combined immunity (ie, natural and vaccine-induced immunity; n=32). We applied linear regression to compare anti-S titers between the groups, controlling for age, race and ethnicity, and time between vaccination or infection (whichever came last) and sample collection. Anti-S titers were 57.3% and 94.4% lower among those with vaccine-induced and natural immunity, respectively, compared with those with combined immunity ( P <.001, P =.005).

Comparing SARS-CoV-2 neutralizing antibody levels in convalescent unvaccinated, convalescent vaccinated, and naive vaccinated subjects

Background

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in December 2019 and spread rapidly. The purpose of this study was to compare neutralizing antibodies (NAbs) following the original booster vaccine in convalescent and naive vaccinated individuals and in a third comparison group consisting of unvaccinated convalescent plasma donors.

Methods

We assessed NAbs before and 2 months after a booster vaccine in 68 adults who had completed the initial vaccine series for SARS-CoV-2. Of these subjects, 58 had no history of prior infection (naïve vaccinated group) and 10 had been infected with SARS-COV-2 prior to the completing the first vaccine series (convalescent vaccinated group). A third comparison group included unvaccinated convalescent plasma donors (n = 55) from an earlier study with NAbs assessed approximately 2 months after a positive test for SARS-CoV-2.

Results

Prior to the booster, convalescent vaccinated subjects had higher NAbs compared to naive vaccinated subjects (p = 0.02). Two months following the booster, NAbs increased in both vaccinated groups. The naive vaccinated group increased more than the convalescent vaccinated group (p = 0.02). NAbs in the naive vaccinated group were almost four times higher than NAbs in the 55 unvaccinated subjects, while the convalescent vaccinated group had levels 2.5 times higher p < 0.01.

Conclusion

NAbs in both vaccinated/boosted groups were significantly higher than in the convalescent unvaccinated group (p < 0.01). Our data indicates that subjects with a single infection with SARS-CoV-2 did not have the same levels of neutralizing antibodies that we observed in subjects who were either in the convalescent vaccinated or the naive vaccinated groups.

The Impact of Vaccination on COVID-19 Burden of Disease in the Adult and Elderly Population: A Systematic Review of Italian Evidence

COVID-19 is a major global health threat, with millions of confirmed cases and deaths worldwide. Containment and mitigation strategies, including vaccination, have been implemented to reduce transmission and protect the population. We conducted two systematic reviews to collect nonrandomized studies investigating the effects of vaccination on COVID-19-related complications and deaths in the Italian population. We considered studies conducted in Italian settings and written in English that contained data on the effects of vaccination on COVID-19-related mortality and complications. We excluded studies that pertained to the pediatric population. In total, we included 10 unique studies in our two systematic reviews. The results showed that fully vaccinated individuals had a lower risk of death, severe symptoms, and hospitalization compared to unvaccinated individuals. The review also looked at the impact of vaccination on post-COVID-19 syndrome, the effectiveness of booster doses in older individuals, and nationwide adverse events. Our work highlights the crucial role that vaccination campaigns have played in reducing the burden of COVID-19 disease in the Italian adult population, positively impacting the pandemic trajectory in Italy.

Impact of vitamin D3 supplementation on COVID-19 vaccine response and immunoglobulin G antibodies in deficient women: A randomized controlled trial

Background

Immune levels were observed by giving vitamin D supplements to vitamin D deficient women who received the COVID-19 vaccine.

Methods

In the research, there were volunteer women who had received two doses of the COVID-19 vaccine who participated for a mean of more than 65 days. Group D (n=14 Pfizer-BioNTech, 2 Sinovac) received 150,000 IU of vitamin D supplementation, but group C (n=14 Pfizer-BioNTech), 3 Sinovac) no support was provided.

Results

When the consumption of vitamin D ends (D group), serum 25-Hydroxy Vitamin D levels were found to increase regularly in the (W3) last measurements (p=0.001). There was no significant difference in immunoglobulin M levels between groups D and C (Control group) (p=0.063). It was observed that the immunoglobulin G levels reached the peak level between the W1 and W2 measurements of the D group (P<0.001) and there were significant differences between the three sizes. Also, no correlation was found between the D group's initial serum immunoglobulin G and 25-Hydroxy Vitamin D levels. However, when the final measurements were examined, a significant positive correlation was found between immunoglobulin G and 25-Hydroxy Vitamin D levels (r=0.558, p=0.031).

Conclusion

It was determined that serum IgG levels increased significantly depending on the duration between those who used vitamin D and those who did not and it was above the initial level for a long time. A positive and significant relationship was found between the last measured immunoglobulin G and 25(OH) D levels while vitamin D supplementation continued.

Trial Registration: This study registered under ClinicalTrials.gov (Identifier no. NCT05447065)

Short-Lived Antibody-Mediated Saliva Immunity against SARS-CoV-2 after Vaccination

Knowledge about the effect of vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on immunity reflected in the saliva is sparse. We examined the antibody response in saliva compared to that in serum 2 and 6 months after the first vaccination with the BNT162b2 vaccine. Four hundred fifty-nine health care professionals were included in a prospective observational study measuring antibody levels in saliva and corresponding serum samples at 2 and 6 months after BNT162b2 vaccination. Vaccinated, previously SARS-CoV-2-infected individuals (hybrid immunity) had higher IgG levels in saliva at 2 months than vaccinated, infection-naive individuals (P < 0.001). After 6 months, saliva IgG levels declined in both groups (P < 0.001), with no difference between groups (P = 0.37). Furthermore, serum IgG levels declined from 2 to 6 months in both groups (P < 0.001). IgG antibodies in saliva and serum correlated in individuals with hybrid immunity at 2 and 6 months (ρ = 0.58, P = 0.001, and ρ = 0.53, P = 0.052, respectively). In vaccinated, infection-naive individuals, a correlation was observed at 2 months (ρ = 0.42, P < 0.001) but not after 6 months (ρ = 0.14, P = 0.055). IgA and IgM antibodies were hardly detectable in saliva at any time point, regardless of previous infection. In serum, IgA was detected at 2 months in previously infected individuals. BNT162b2 vaccination induced a detectable IgG anti-SARS-CoV-2 RBD response in saliva at both 2 and 6 months after vaccination, being more prominent in previously infected than infection-naive individuals. However, a significant decrease in salivary IgG was observed after 6 months, suggesting a rapid decline in antibody-mediated saliva immunity against SARS-CoV-2, after both infection and systemic vaccination. IMPORTANCE Knowledge about the persistence of salivary immunity after SARS-CoV-2 vaccination is limited, and information on this topic could prove important for vaccine strategy and development. We hypothesized that salivary immunity would wane rapidly after vaccination. We measured anti-SARS-CoV-2 IgG, IgA, and IgM concentrations in saliva and serum in both previously infected and infection-naive individuals, 2 and 6 months after first vaccination with BNT162b2, in 459 hospital employees from Copenhagen University Hospital. We observed that IgG was the primary salivary antibody 2 months after vaccination in both previously infected and infection-naive individuals, but dropped significantly after 6 months. Neither IgA nor IgM was detectable in saliva at either time point. Findings indicate that salivary immunity against SARS-CoV-2 rapidly declines following vaccination in both previously infected and infection-naive individuals. We believe this study shines a light on the workings of salivary immunity after SARS-CoV-2 infection, which could prove relevant for vaccine development.

A heterologous AZD1222 priming and BNT162b2 boosting regimen more efficiently elicits neutralizing antibodies, but not memory T cells, than the homologous BNT162b2 regimen

BACKGROUND

Comparative analyses of SARS-CoV-2-specific immune responses elicited by diverse prime-boost regimens are required to establish efficient regimens for the control of COVID-19.

METHOD

In this prospective observational cohort study, spike-specific immunoglobulin G (IgG) and neutralizing antibodies (nAbs) alongside spike-specific T-cell responses in age-matched groups of homologous BNT162b2/BNT162b2 or AZD1222/AZD1222 vaccination, heterologous AZD1222/BNT162b2 vaccination, and prior wild-type SARS-CoV-2 infection/vaccination were evaluated.

RESULTS

Peak immune responses were achieved after the second vaccine dose in the naïve vaccinated groups and after the first dose in the prior infection/vaccination group. Peak titers of anti-spike IgG and nAb were significantly higher in the AZD1222/BNT162b2 vaccination and prior infection/vaccination groups than in the BNT162b2/BNT162b2 or AZD1222/AZD1222 groups. However, the frequency of interferon-γ-producing CD4⁺ T cells was highest in the BNT162b2/BNT162b2 vaccination group. Similar results were observed in the analysis of polyfunctional T cells. When nAb and CD4⁺T-cell responses against the Delta variant were analyzed, the prior infection/vaccination group exhibited higher responses than the groups of other homologous or heterologous vaccination regimens.

CONCLUSION

nAbs are efficiently elicited by heterologous AZD1222/BNT162b2 vaccination, as well as prior infection/vaccination, whereas spike-specific CD4⁺T-cell responses are efficiently elicited by homologous BNT162b2 vaccination. Variant-recognizing immunity is more efficiently generated by prior infection/vaccination than the other homologous or heterologous vaccination regimens.

Durability of ChAdOx1 nCoV-19 (AZD1222) vaccine and hybrid humoral immunity against variants including omicron BA.1 and BA.4 6 months after vaccination (COV005): a post-hoc analysis of a randomised, phase 1b-2a trial

BACKGROUND

COVID-19 vaccine rollout is lagging in Africa, where there has been a high rate of SARS-CoV-2 infection. We aimed to evaluate the effect of SARS-CoV-2 infection before vaccination with the ChAdOx-nCoV19 (AZD1222) vaccine on antibody responses through to 180 days.

METHODS

We did an unmasked post-hoc immunogenicity analysis after the first and second doses of AZD1222 in a randomised, placebo-controlled, phase 1b-2a study done in seven locations in South Africa. AZD1222 recipients who were HIV-uninfected, were stratified into baseline seropositive or seronegative groups using the serum anti-nucleocapsid (anti-N) immunoglobulin G (IgG) electroluminescence immunoassay to establish SARS-CoV-2 infection before the first dose of AZD1222. Binding IgG to spike (anti-S) and receptor binding domain (anti-RBD) were measured before the first dose (day 0), second dose (day 28), day 42, and day 180. Neutralising antibody (NAb) against SARS-CoV-2 variants D614G, beta, delta, gamma, and A.VOI.V2, and omicron BA1 and BA.4 variants, were measured by pseudovirus assay (day 28, day 42, and day 180). This trial is registered with ClinicalTrials.gov, NCT04444674, and the Pan African Clinicals Trials Registry, PACTR202006922165132.

FINDINGS

Of 185 individuals who were randomly assigned to AZD1222, we included 91 individuals who were baseline seropositive and 58 who were baseline seronegative, in the final analysis. In the seropositive group, there was little change of anti-S IgG (and anti-RBD IgG) or neutralising antibody (NAb) titres at day 42 compared with at day 28. Anti-S (and anti-RBD) IgG geometric mean concentrations (GMCs) were higher throughout in the seropositive compared with the seronegative group, including at day 180 (GMCs 517·8 [95% CI 411·3-651·9] vs 82·1 [55·2-122·3] BAU/mL). Also D614G NAb geometric mean titres (GMTs) were higher in the seropositive group than the seronegative group, as was the percentage with titres of at least 185 (80% putative risk reduction threshold [PRRT] against wild-type-alpha COVID-19), including at day 180 (92·0% [74·0-99·0] vs 18·2% [2·3-51·8). Similar findings were observed for beta, A.VOI.V2, and gamma. For delta, BA.1, and BA.4, NAb GMTs and the proportion with titres above the PRRT were substantially higher in the seropositive compared with seronegative group at day 28 and day 42, but no longer differed between the groups by day 180.

INTERPRETATION

A single dose of AZD1222 in the general African population, where COVID-19 vaccine coverage is low and SARS-CoV-2 seropositivity is 90%, could enhance the magnitude and quality of antibody responses to SARS-CoV-2.

FUNDING

The Bill & Melinda Gates Foundation, the South African Medical Research Council, the UK Research and Innovation, the UK National Institute for Health Research, and the South African Medical Research Council.

TRANSLATION

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

Effects of the second dose of COVID-19 vaccines in patients with autoimmune rheumatic diseases with hybrid immunity

Patients with autoimmune rheumatic diseases with a previous infection by the SARS-CoV-2 virus have exaggerated responses to a single dose of COVID-19 vaccination as compared to fully vaccinated infection naive patients. The second dose is currently recommended at an extended gap after the infection, but the information available regarding response to the second dose in this subgroup is limited. Patients with AIRDs previously infected with COVID-19, who have received at least one dose of AZD1222/ChAdOx1 (n = 200) were included and stratified based on vaccine doses (V), and infection (I) into I + V, I + V + V, V + I, V + V + I. Anti-RBD (receptor binding domain) antibodies were compared across the four groups. In 49 patients of the I + V + V group (AZD12222), paired sera were compared for antibody levels and neutralization after each vaccine dose. Thirty patients with hybrid immunity after BBV152 and 25 with complete vaccination without infection were included as controls. The highest anti-RBD antibody levels were observed in the V + V + I group (18,219 ± 7702 IU/ml) with statistically similar titers in the I + V + V (10,392 ± 8514 IU/ml) and the I + V (8801 ± 8122 IU/ml). This was confirmed in the 49 paired samples that paradoxically showed a lowering of antibody titers after the second dose [9626 (IQR: 4575-18,785)-5781 (2484-11,906); p < 0.001]. Neutralization of the Delta variant was unaffected but Omicron neutralization was significantly reduced after the second dose [45.7 (5.3-86.53)-35% (7.3-70.9); p = 0.028]. Ancillary analyses showed that only the hybrid immune sera could neutralize the Omicron variant and AZD1222 hybrids performed better than BBV152 hybrids. The second dose of AZD1222 did not boost antibody titers in patients with RD who had COVID-19 previously. In the analysis of paired sera, the second dose led to a statistically significant reduction in antibody titers and also reduced neutralization of the Omicron variant.

Immunological Findings in a Group of Individuals Who Were Poor or Non-Responders to Standard Two-Dose SARS-CoV-2 Vaccines

Coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been declared a pandemic. However, data on the poor or non-responders to SARS-CoV-2 vaccines in the general population are limited. The objective of this study was to comprehensively compare the immunological characteristics of poor or non-responders to SARS-CoV-2 vaccines in the 18-59-year group with those in the ≥60-year group using internationally recognized cut-off values. The main outcome was effective seroconversion characterized by an anti-SARS-CoV-2 spike IgG level of at least a four-fold increase from baseline. Profiling of naïve immune cells was analyzed prior to vaccination to demonstrate baseline immunity. The outcomes of effective seroconversion in patients aged 18-59 years with those in patients aged ≥60 years were compared. The quantitative level of anti-spike IgG was significantly lower in individuals aged ≥60 and men aged 18-59 years. There were 7.5% of poor or non-responders among the 18-59 years and 11.7% of poor or non-responders in the ≥60 years using a four-fold increase parameter. There were 37.0-58.1% with low lymphocyte count (<1000/mm³), 33.3-45.2% with low CD4 cell counts (<500/mm³), and 74.1-96.8% with low B cell counts (<100/mm³) in the non-seroconversion group. An individual with an anti-SARS-CoV-2 spike IgG titer below 50 BAU/mL might be considered a poor or non-responder between 14 and 90 days after the last vaccine dose. Booster vaccination or additional protective measures should be recommended to poor or non-responders as soon as possible to reduce disease severity and mortality.

Age-dependent impairment in antibody responses elicited by a homologous CoronaVac booster dose

The emergence of the SARS-CoV-2 Omicron sublineages resulted in increased transmission rates and reduced protection from vaccines. To counteract these effects, multiple booster strategies were used in different countries, although data comparing their efficiency in improving protective immunity remain sparse, especially among vulnerable populations, including older adults. The inactivated CoronaVac vaccine was among the most widely distributed vaccine worldwide and was essential in the early control of SARS-CoV-2-related hospitalizations and deaths. However, it is not well understood whether homologous versus heterologous booster doses in those fully vaccinated with CoronaVac induce distinct humoral responses or whether these responses vary across age groups. We analyzed plasma antibody responses from CoronaVac-vaccinated younger or older individuals who received a homologous CoronaVac or heterologous BNT162b2 or ChAdOx1 booster vaccine. All three evaluated boosters resulted in increased virus-specific IgG titers 28 days after the booster dose. However, we found that both IgG titers against SARS-CoV-2 Spike or RBD and neutralization titers against Omicron sublineages were substantially reduced in participants who received homologous CoronaVac compared with the heterologous BNT162b2 or ChAdOx1 booster. This effect was specifically prominent in recipients >50 years of age. In this group, the CoronaVac booster induced low virus-specific IgG titers and failed to elevate neutralization titers against any Omicron sublineage. Our results point to the notable inefficiency of CoronaVac immunization and boosting in mounting protective antiviral humoral immunity, particularly among older adults, during the Omicron wave. These observations also point to benefits of heterologous regimens in high-risk populations fully vaccinated with CoronaVac.

Effectiveness of a Second Dose of an mRNA Vaccine Against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Omicron Infection in Individuals Previously Infected by Other Variants

BACKGROUND

Single-dose vaccination was widely recommended in the pre-Omicron era for persons with previous SARS-CoV-2 infection. The effectiveness of a second vaccine dose in this group in the Omicron era is unknown.

METHODS

We linked nationwide population registries in Spain to identify community-dwelling individuals aged 18-64, with a positive SARS-CoV-2 test before single-dose mRNA vaccination (mRNA-1273 or BNT162b2). Every day between 3 January and 6 February 2022 we matched 1:1 individuals receiving a second mRNA vaccine dose and controls on sex, age, province, first dose type and time, month of primary infection, and number of previous tests. We then estimated Kaplan-Meier risks of confirmed SARS-CoV-2 reinfection. We performed a similar analysis in a Delta-dominant period, between 19 July and 30 November 2021.

RESULTS

In the Omicron period, estimated effectiveness (95% CI) of a second dose was 62.2% (58.2-66.4%) 7-34 days after administration, similar across groups defined by age, sex, type of first vaccine, and time since the first dose. Estimated effectiveness was 65.4% (61.1-69.9%) for mRNA-1273 and 52.0% (41.8-63.1%) for BNT162b2. Estimated effectiveness was 78.5% (67.4-89.9%), 66.1% (54.9-77.5%), and 60.2% (55.5-64.8%) when primary infection had occurred in the Delta, Alpha, and pre-Alpha periods, respectively. In the Delta period, the estimated effectiveness of a second dose was 8.8% (-55.3% to 81.1%).

CONCLUSIONS

Our results suggest that, over 1 month after administration, a second dose of mRNA vaccine increases protection against SARS-CoV-2 reinfection with the Omicron variant among individuals with single-dose vaccination and previously infected with another variant.

Protective roles and protective mechanisms of neutralizing antibodies against SARS-CoV-2 infection and their potential clinical implications

Neutralizing antibodies (NAbs) are central players in the humoral immunity that defends the body from SARS-CoV-2 infection by blocking viral entry into host cells and neutralizing their biological effects. Even though NAbs primarily work by neutralizing viral antigens, on some occasions, they may also combat the SARS-CoV-2 virus escaping neutralization by employing several effector mechanisms in collaboration with immune cells like natural killer (NK) cells and phagocytes. Besides their prophylactic and therapeutic roles, antibodies can be used for COVID-19 diagnosis, severity evaluation, and prognosis assessment in clinical practice. Furthermore, the measurement of NAbs could have key implications in determining individual or herd immunity against SARS-CoV-2, vaccine effectiveness, and duration of the humoral protective response, as well as aiding in the selection of suitable individuals who can donate convalescent plasma to treat infected people. Despite all these clinical applications of NAbs, using them in clinical settings can present some challenges. This review discusses the protective functions, possible protective mechanisms against SARS-CoV-2, and potential clinical applications of NAbs in COVID-19. This article also highlights the possible challenges and solutions associated with COVID-19 antibody-based prophylaxis, therapy, and vaccination.

Assessment of early and post COVID-19 vaccination antibody response in healthcare workers: a multicentre cross-sectional study on inactivated, mRNA and vector-based vaccines

In this multicentre study, we compared the status of antibody production in healthcare personnel (HCP) before and after vaccination using different brands of COVID-19 vaccines between March 2021 and September 2021. Out of a total of 962 HCP enrolled in our study, the antibody against the S1 domain of SARS-CoV-2 was detected in 48.3%, 95.5% and 96.2% of them before, after the first and the second doses of the vaccines, respectively. Our results showed post-vaccination infection in 3.7% and 5.9% of the individuals after the first and second doses of vaccines, respectively. The infection was significantly lower in HCP who presented higher antibody titres before the vaccination. Although types of vaccines did not show a significant difference in the infection rate, a lower infection rate was recorded for AstraZeneca after the second vaccination course. This rate was equal among individuals receiving a second dose of Sinopharm and Sputnik. Vaccine-related side effects were more frequent among AstraZeneca recipients after the first dose and among Sputnik recipients after the second dose. In conclusion, our results showed diversity among different brands of COVID-19 vaccines; however, it seems that two doses of the vaccines could induce an antibody response in most of HCP. The induced immunity could persist for 3-5 months after the second vaccination course.

Neutralizing antibodies and T-cell responses to inactivated SARS-CoV-2 vaccine in COVID-19 convalescents one and a half years after infection

Vaccines have been considered the most promising solution for ending the coronavirus disease 2019 (COVID-19) pandemic. Information regarding neutralizing antibodies (NAbs) and T-cell immune response in inactivated SARS-CoV-2 vaccine-immunized COVID-19 convalescent patients were either only available for a short time after illness recovered or not available at all (T-cell immunity). We evaluated SARS-CoV-2 NAbs and cellular immune responses to the SARS-CoV-2 inactivated vaccine in convalescent patients who recovered from infection for about one and a half years. We found that compared to before vaccination, SARS-CoV-2 NAbs and specific T-cell responses were significantly boosted by the inactivated vaccine in convalescent patients, which confirmed the pre-existing adaptive immunity in SARS-CoV-2 infected people. We observed that NAbs and IFN-γ-secreting T-cell response elicited by a single vaccine dose in subjects with prior COVID-19 infection were higher than after two doses of vaccine in SARS-CoV-2 naïve subjects. Both humoral and cellular immune responses elicited by one and two doses of inactivated vaccine were comparable in COVID-19-recovered persons. In conclusion, inactivated COVID-19 vaccine induced robust NAbs and T-cell responses to SARS-CoV-2 in COVID-19 convalescent patients and immune responses after one dose were equal to that after receiving two doses, which highlighted that robust humoral and cellular immune response can be reactivated by the inactivated vaccine in SARS-CoV-2 convalescent patients.

The humoral immune response more than one year after SARS-CoV-2 infection: low detection rate of anti-nucleocapsid antibodies via Euroimmun ELISA

PURPOSE

Antibody assays against SARS-CoV-2 are used in sero-epidemiological studies to estimate the proportion of a population with past infection. IgG antibodies against the spike protein (S-IgG) allow no distinction between infection and vaccination. We evaluated the role of anti-nucleocapsid-IgG (N-IgG) to identify individuals with infection more than one year past infection.

METHODS

S- and N-IgG were determined using the Euroimmun enzyme-linked immunosorbent assay (ELISA) in two groups: a randomly selected sample from the population of Stuttgart, Germany, and individuals with PCR-proven SARS-CoV-2 infection. Participants were five years or older. Demographics and comorbidities were registered from participants above 17 years.

RESULTS

Between June 15, 2021 and July 14, 2021, 454 individuals from the random sample participated, as well as 217 individuals with past SARS-CoV-2 infection. Mean time from positive PCR test result to antibody testing was 458.7 days (standard deviation 14.6 days) in the past infection group. In unvaccinated individuals, the seroconversion rate for S-IgG was 25.5% in the random sample and 75% in the past infection group (P = < 0.001). In vaccinated individuals, the mean signal ratios for S-IgG were higher in individuals with prior infection (6.9 vs 11.2; P = < 0.001). N-IgG were only detectable in 17.1% of participants with past infection. Predictors for detectable N-IgG were older age, male sex, fever, wheezing and in-hospital treatment for COVID-19 and cardiovascular comorbidities.

CONCLUSION

N-IgG is not a reliable marker for SARS-CoV-2 infection after more than one year. In future, other diagnostic tests are needed to identify individuals with past natural infection.

Evolution of antibody profiles against SARS-CoV-2 in experienced and naïve vaccinated elderly people

Introduction

The third dose of the COVID-19 vaccine is especially necessary in people over 65 years of age due to their lower immune response.

Methods

We designed a multicentre, prospective observational study including 98 people ≤65 years old who lived in two nursing homes in Valladolid, Spain. One of the groups had previous experience with SARS-CoV-2 (n=68;69.4%) and the other was naïve (n=30;30.6%). We evaluated the response to the three doses of the Comirnaty vaccine and the dynamics of antibodies during 5 consecutive serum samplings: 2 after the first two doses of vaccination, one three months after the first dose, another at 6 months and the last one month after the third dose. IgG antibodies against SARS-CoV-2 S1, RBD and N antigens were analysed.

Results

Both groups increased the level of Abs against S1 and RBD, but the experienced group showed a 130-fold higher humoral response due to hybrid immunisation (infection+vaccination). The response to vaccination with Comirnaty against COVID-19 was higher in those ≤65 years with previous experience than those who were naïve. However, the amount of antibodies against S1 and RBD equalised at 6 months. After the third dose, both groups raised the amount of antibodies to a similar level. The reinfections suggested by the analysis of antibodies against N were frequent in both groups.

Discussion

The third dose showed a clear benefit for elderly people, with the reinforcement of the antibody levels after the decline suffered after six months of the first two doses.

Mathematical modelling of the waning of anti-RBD IgG SARS-CoV-2 antibody titers after a two-dose BNT162b2 mRNA vaccination

Background

After exposure to SARS-CoV-2 and/or vaccination there is an increase in serum antibody titers followed by a non-linear waning. Our aim was to find out if this waning of antibody titers would fit to a mathematical model.

Methods

We analyzed anti-RBD (receptor binding domain) IgG antibody titers and the breakthrough infections over a ten-month period following the second dose of the mRNA BNT162b2 (Pfizer-BioNtech.) vaccine, in a cohort of 54 health-care workers (HCWs) who were either never infected with SARS-CoV-2 (naïve, nHCW group, n=27) or previously infected with the virus (experienced, eHCW group, n=27). Two mathematical models, exponential and power law, were used to quantify antibody waning kinetics, and we compared the relative quality of the goodness of fit to the data between both models was compared using the Akaik Information Criterion.

Results

We found that the waning slopes were significantly more pronounced for the naïve when compared to the experienced HCWs in exponential (p-value: 1.801E-9) and power law (p-value: 9.399E-13) models. The waning of anti-RBD IgG antibody levels fitted significantly to both exponential (average-R2: 0.957 for nHCW and 0.954 for eHCW) and power law (average-R2: 0.991 for nHCW and 0.988 for eHCW) models, with a better fit to the power law model. In the nHCW group, titers would descend below an arbitrary 1000-units threshold at a median of 210.6 days (IQ range: 74.2). For the eHCW group, the same risk threshold would be reached at 440.0 days (IQ range: 135.2) post-vaccination.

Conclusion

Two parsimonious models can explain the anti-RBD IgG antibody titer waning after vaccination. Regardless of the model used, eHCWs have lower waning slopes and longer persistence of antibody titers than nHCWs. Consequently, personalized vaccination booster schedules should be implemented according to the individual persistence of antibody levels.

Long-term persistence of IgG antibodies in recovered COVID-19 individuals at 18 months post-infection and the impact of two-dose BNT162b2 (Pfizer-BioNTech) mRNA vaccination on the antibody response: Analysis using fixed-effects linear regression model

This era of emerging variants needs a thorough evaluation of data on the long-term efficacy of immune responses in vaccinated as well as recovered individuals, to understand the overall evolution of the pandemic. In this study, we aimed to assess the dynamics of IgG response over 18 months in n = 36 patients from the Umbria region in Italy, who had a documented history of COVID-19 infection in March 2020, and then compared the impact of two-dose BNT162b2 (Pfizer-BioNTech) vaccination on the antibody responses of these patients with the ones who did not receive any dose of vaccine. This is the longest observation (March 2020-September 2021) for the presence of antibodies against SARS-CoV-2 in recovered individuals along with the impact of 2 dose-BNT162b2 vaccination on these responses. Fixed-effect regression models were used for statistical analysis which could be also used to predict future titer trends. At 18 months, 97% participants tested positive for anti-NCP hinting towards the persistence of infection-induced immunity even for the vaccinated individuals. Our study findings demonstrate that while double dose vaccination boosted the IgG levels in recovered individuals 161 times, this "boost" was relatively short-lived. The unvaccinated recovered individuals, in contrast, continued to show a steady decline but detectable antibody levels. Further studies are required to re-evaluate the timing and dose regimen of vaccines for an adequate immune response in recovered individuals.

COVID-19 vaccine immunogenicity in people with HIV

OBJECTIVES

Many vaccines require higher/additional doses or adjuvants to provide adequate protection for people with HIV (PWH). Our objective was to compare COVID-19 vaccine immunogenicity in PWH to HIV-negative individuals.

DESIGN

In a Canadian multi-center prospective, observational cohort of PWH receiving at least two COVID-19 vaccinations, we measured vaccine-induced immunity at 3 and 6 months post 2nd and 1-month post 3rd doses.

METHODS

The primary outcome was the percentage of PWH mounting vaccine-induced immunity [co-positivity for anti-IgG against SARS-CoV2 Spike(S) and receptor-binding domain proteins] 6 months post 2nd dose. Univariable and multivariable logistic regressions were used to compare COVID-19-specific immune responses between groups and within subgroups.

RESULTS

Data from 294 PWH and 267 controls were analyzed. Immunogenicity was achieved in over 90% at each time point in both groups. The proportions of participants achieving comparable anti-receptor-binding domain levels were similar between the group at each time point. Anti-S IgG levels were similar by group at month 3 post 2nd dose and 1-month post 3rd dose. A lower proportion of PWH vs. controls maintained vaccine-induced anti-S IgG immunity 6 months post 2nd dose [92% vs. 99%; odds ratio: 0.14 (95% confidence interval: 0.03, 0.80; P = 0.027)]. In multivariable analyses, neither age, immune non-response, multimorbidity, sex, vaccine type, or timing between doses were associated with reduced IgG response.

CONCLUSION

Vaccine-induced IgG was elicited in the vast majority of PWH and was overall similar between groups. A slightly lower proportion of PWH vs. controls maintained vaccine-induced anti-S IgG immunity 6 months post 2nd dose demonstrating the importance of timely boosting in this population.

SARS-CoV-2 spike conformation determines plasma neutralizing activity elicited by a wide panel of human vaccines

Numerous safe and effective coronavirus disease 2019 vaccines have been developed worldwide that use various delivery technologies and engineering strategies. We show here that vaccines containing prefusion-stabilizing S mutations elicit antibody responses in humans with enhanced recognition of S and the S1 subunit relative to postfusion S as compared with vaccines lacking these mutations or natural infection. Prefusion S and S1 antibody binding titers positively and equivalently correlated with neutralizing activity, and depletion of S1-directed antibodies completely abrogated plasma neutralizing activity. We show that neutralizing activity is almost entirely directed to the S1 subunit and that variant cross-neutralization is mediated solely by receptor binding domain-specific antibodies. Our data provide a quantitative framework for guiding future S engineering efforts to develop vaccines with higher resilience to the emergence of variants than current technologies.

Mucosal and Systemic Responses to Severe Acute Respiratory Syndrome Coronavirus 2 Vaccination Determined by Severity of Primary Infection

With much of the world infected with or vaccinated against severe acute respiratory syndrome coronavirus 2 (commonly abbreviated SARS-CoV-2; abbreviated here SARS2), understanding the immune responses to the SARS2 spike (S) protein in different situations is crucial to controlling the pandemic. We studied the clinical, systemic, mucosal, and cellular responses to two doses of SARS2 mRNA vaccines in 62 individuals with and without prior SARS2 infection that were divided into three groups based on antibody serostatus prior to vaccination and/or degree of disease symptoms among those with prior SARS2 infection: antibody negative (naive), low symptomatic, and symptomatic. Antibody negative were subjects who were antibody negative (i.e., those with no prior infection). Low symptomatic subjects were those who were antibody negative and had minimal or no symptoms at time of SARS2 infection. Symptomatic subjects were those who were antibody positive and symptomatic at time of SARS2 infection. All three groups were then studied when they received their SARS2 mRNA vaccines. In the previously SARS2-infected (based on antibody test) low symptomatic and symptomatic groups, reactogenic symptoms related to a recall response were elicited after the first vaccination. Anti-S trimer IgA and IgG titers, and neutralizing antibody titers, peaked after the 1st vaccination in the previously SARS2-infected groups and were significantly higher than for the SARS2 antibody-negative group in the plasma and nasal samples at most time points. Nasal and plasma IgA antibody responses were significantly higher in the low symptomatic group than in the symptomatic group at most time points. After the first vaccination, differences in cellular immunity were not evident between groups, but the activation-induced cell marker (AIM+) CD4+ cell response correlated with durability of IgG humoral immunity against the SARS2 S protein. In those SARS2-infected subjects, severity of infection dictated plasma and nasal IgA responses in primary infection as well as response to vaccination (peak responses and durability), which could have implications for continued protection against reinfection. Lingering differences between the SARS2-infected and SARS2-naive up to 10 months postvaccination could explain the decreased reinfection rates in the SARS2-infected vaccinees recently reported and suggests that additional strategies (such as boosting of the SARS2-naive vaccinees) are needed to narrow the differences observed between these groups. IMPORTANCE This study on SARS2 vaccination in those with and without previous exposure to the virus demonstrates that severity of infection dictates IgA responses in primary infection as well as response to vaccination (peak responses and durability), which could have implications for continued protection against reinfection.

Strong Neutralizing Antibody Responses to SARS-CoV-2 Variants Following a Single Vaccine Dose in Subjects With Previous SARS-CoV-2 Infection

BACKGROUND

Previous severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection primes the immune system; thus individuals who have recovered from infection have enhanced immune responses to subsequent vaccination (hybrid immunity). However, it remains unclear how well hybrid immunity induced by severe or mild infection can cross-neutralize emerging variants. We aimed to compare the strength and breadth of antibody responses in vaccinated recovered and uninfected subjects.

METHODS

We measured spike-specific immunoglobulin (Ig)G and neutralizing antibodies (NAbs) from vaccinated subjects including 320 with hybrid immunity and 20 without previous infection. From 29 subjects with a previous severe or mild infection, we also measured NAb responses against Alpha (B.1.1.7), Beta (B.1.351), Delta (B.1.617.2), and Omicron (B.1.1.529/BA.1) variants following vaccination.

RESULTS

A single vaccine dose induced 2-fold higher anti-spike IgG concentrations and up to 4-fold higher neutralizing potency of antibodies in subjects with a previous infection compared with vaccinated subjects without a previous infection. Hybrid immunity was more enhanced after a severe than a mild infection, with sequentially decreasing NAb titers against Alpha, Beta, Delta, and Omicron variants. We found similar IgG concentrations in subjects with a previous infection after 1 or 2 vaccine doses.

CONCLUSIONS

Hybrid immunity induced strong IgG responses, particularly after severe infection. However, the NAb titers were low against heterologous variants, especially against Omicron.

Broad and durable antibody response after vaccination with inactivated SARS-CoV-2 in individuals with a history of 2003 SARS-CoV infection

In vaccinees who were infected with SARS-CoV in 2003, we observed greater antibody responses against spike and nucleoprotein of both SARS-CoV-2 and SARS-CoV after a single dosage of inactivated SARS-CoV-2 vaccine. After receiving the second vaccination, antibodies against RBD of SARS-CoV-2 Wuhan, Beta, Delta, and recently emerged Omicron are significantly higher in SARS-CoV experienced vaccinees than in SARS-CoV naïve vaccinees. Neutralizing activities measured by authentic viruses and pseudoviruses of SARS-CoV, SARS-CoV-2 Wuhan, Beta, and Delta are greater in SARS-CoV experienced vaccinees. In contrast, only weak neutralizing activities against SARS-CoV-2 and variants were detected in SARS-CoV naïve vaccinees. By 6 months after the second vaccination, neutralizing activities were maintained at a relatively higher level in SARS-CoV experienced vaccinees but were undetectable in SARS-CoV naïve vaccinees. These findings suggested a great possibility of developing a universal vaccine by heterologous vaccination using spike antigens from different SARS-related coronaviruses.

Likelihood of COVID-19 reinfection in an urban community cohort in Massachusetts

Background

Understanding the association of prior SARS-CoV-2 infection with subsequent reinfection has public health relevance.

Objective

To explore COVID-19 severity and SARS-CoV-2 infection and reinfection rates.

Design

Retrospective cohort study.

Setting

Boston, Massachusetts, during the first COVID-19 surge (01/01/2020-05/31/2020; Period-1) and after the first surge (06/01/2020-02/28/2021; Period-2); Period-2 included the second surge (11/01/2020-02/28/2021).

Participants

Patients in an academic medical center and six community health centers who received a clinical diagnosis of COVID-19 between 01/01/2020 and 05/31/2020 or SARS-CoV-2 testing between 01/01/2020 and 02/28/2021.

Measurements

COVID-19 severity was compared between Period-1 and Period-2. Poisson regression models adjusted for demographic variables, medical comorbidities, and census tract were used to assess reinfection risk among patients with COVID-19 diagnoses or SARS-CoV-2 testing during Period-1 and additional SARS-CoV-2 testing during Period-2.

Results

Among 142,047 individuals receiving SARS-CoV-2 testing or clinical diagnoses during the study period, 15.8% were infected. Among COVID-19 patients, 22.5% visited the emergency department, 13% were hospitalized, and 4% received critical care. Healthcare utilization was higher during Period-1 than Period-2 (22.9% vs. 18.9% emergency department use, 14.7% vs. 9.9% hospitalization, 5.5% vs. 2.5% critical care; p < 0.001). Reinfection was assessed among 8961 patients with a SARS-CoV-2 test or COVID-19 diagnosis in Period-1 who underwent additional testing in Period-2. A total of 2.7% (n = 65/2431) with SARS-CoV-2 in Period-1 tested positive in Period-2, compared with 12.6% (n = 821/6530) of those who initially tested negative (IRR of reinfection = 0.19, 95% CI: 0.15-0.25).

Conclusions

Prior SARS-CoV-2 infection among this observational cohort was associated with an 81% lower reinfection rate.

SARS-CoV-2 antibody responses post-vaccination in UK healthcare workers with pre-existing medical conditions: a cohort study

OBJECTIVES

To examine antibody responses after the second vaccination in healthcare workers (HCWs) with underlying health conditions.

DESIGN

Cohort study.

SETTING

Oxford University Hospitals in the United Kingdom.

PARTICIPANTS

Healthcare workers who had SARS-CoV-2 serological data available and received two SARS-CoV- 2 vaccinations.

PRIMARY OUTCOME

Peak SARS-CoV-2 anti-spike IgG responses after the second vaccination and associations with underlying health conditions and the estimated risk of severe COVID-19 using an occupational health risk assessment tool.

METHODS

We used univariable and multivariable linear regression models to investigate associations between antibody levels and demographics (age, sex, ethnicity), healthcare role, body mass index, underlying health conditions, vaccination status, prior infection and the Association of Local Authority Medical Advisors COVID-age risk score.

RESULTS

1635 HCWs had anti-spike IgG measurements 14-84 days after second vaccination and data on any underlying health conditions. Only five HCWs (0.3%), all on immunosuppressive treatment, (including four organ transplant recipients), did not seroconvert after second vaccination. Antibody levels were independently lower with older age, diabetes, immunosuppression, respiratory disorders other than asthma and markedly so in organ transplant recipients. Levels were independently lower in ChAdOx1 versus BNT162b2 recipients and higher following previous infection. HCWs with 'very high' COVID-age risk scores had lower median antibody levels than those with 'low', 'medium' or 'high' risk scores; 4379 AU/mL, compared with 12 337 AU/mL, 9430 AU/mL and 10 524 AU/mL, respectively.

CONCLUSIONS

Two vaccine doses are effective in generating antibody responses among HCWs, including those with a high occupational risk. However, HCWs with underlying health conditions, especially diabetes, immunosuppression and organ transplant, had lower antibody levels, and vaccine response monitoring may be needed.

Hospitalization and Mortality by Vaccination Status among COVID-19 Patients Aged ≥ 25 Years in Bangladesh: Results from a Multicenter Cross-Sectional Study

The COVID-19 pandemic has inflicted a massive disease burden globally, involving 623 million confirmed cases with 6.55 million deaths, and in Bangladesh, over 2.02 million clinically confirmed cases of COVID-19, with 29,371 deaths, have been reported. Evidence showed that vaccines significantly reduced infection, severity, and mortality across a wide age range of populations. This study investigated the hospitalization and mortality by vaccination status among COVID-19 patients in Bangladesh and identified the vaccine's effectiveness against severe outcomes in real-world settings. Between August and December 2021, we conducted this cross-sectional survey among 783 RT-PCR-confirmed COVID-19 hospitalized patients admitted to three dedicated COVID-19 hospitals in Bangladesh. The study used a semi-structured questionnaire to collect information. We reviewed the patient's records and gathered COVID-19 immunization status from the study participants or their caregivers. Patients with incomplete or partial data from the record were excluded from enrollment. Logistic regression analyses were performed to determine the association between key variables with a patient's vaccination status and mortality. The study revealed that overall hospitalization, severity, and morality were significantly high among unvaccinated study participants. Only one-fourth (25%) of hospitalized patients were found COVID-19 vaccinated. Morality among unvaccinated COVID-19 study participants was significantly higher (AOR: 7.17) than the vaccinated (11.17% vs. 1.53%). Severity was found to be seven times higher among unvaccinated patients. Vaccination coverage was higher in urban areas (29.8%) compared to rural parts (20.8%), and vaccine uptake was lower among female study participants (22.7%) than male (27.6%). The study highlighted the importance of COVID-19 vaccines in reducing mortality, hospitalization, and other severe consequences. We found a gap in vaccination coverage between urban and rural settings. The findings would encourage the entire population toward immunization and aid the policymakers in the ground reality so that more initiatives are taken to improve vaccination coverage among the pocket population.

High-temporal resolution profiling reveals distinct immune trajectories following the first and second doses of COVID-19 mRNA vaccines

Knowledge of the mechanisms underpinning the development of protective immunity conferred by mRNA vaccines is fragmentary. Here, we investigated responses to coronavirus disease 2019 (COVID-19) mRNA vaccination via high-temporal resolution blood transcriptome profiling. The first vaccine dose elicited modest interferon and adaptive immune responses, which peaked on days 2 and 5, respectively. The second vaccine dose, in contrast, elicited sharp day 1 interferon, inflammation, and erythroid cell responses, followed by a day 5 plasmablast response. Both post-first and post-second dose interferon signatures were associated with the subsequent development of antibody responses. Yet, we observed distinct interferon response patterns after each of the doses that may reflect quantitative or qualitative differences in interferon induction. Distinct interferon response phenotypes were also observed in patients with COVID-19 and were associated with severity and differences in duration of intensive care. Together, this study also highlights the benefits of adopting high-frequency sampling protocols in profiling vaccine-elicited immune responses.