Demographic and clinical characteristics associated with variations in antibody response to BNT162b2 COVID-19 vaccination among healthcare workers at an academic medical centre: a longitudinal cohort analysis

SARS-CoV-2 Humoral Immune Responses in Convalescent Individuals Over 12 Months Reveal Severity-Dependent Antibody Dynamics

Background

Understanding the kinetics and longevity of antibody responses to SARS-CoV-2 is critical to informing strategies toward reducing Coronavirus disease 2019 (COVID-19) reinfections, and improving vaccination and therapy approaches.

Methods

We evaluated antibody titers against SARS-CoV-2 nucleocapsid (N), spike (S), and receptor binding domain (RBD) of spike in 98 convalescent participants who experienced asymptomatic, mild, moderate or severe COVID-19 disease and in 17 non-vaccinated, non-infected controls, using four different antibody assays. Participants were sampled longitudinally at 1, 3, 6, and 12 months post-SARS-CoV-2 positive PCR test.

Findings

Increasing acute COVID-19 disease severity correlated with higher anti-N and anti-RBD antibody titers throughout 12 months post-infection. Anti-N and anti-RBD titers declined over time in all participants, with the exception of increased anti-RBD titers post-vaccination, and the decay rates were faster in hospitalized compared to non-hospitalized participants. <50% of participants retained anti-N titers above control levels at 12 months, with non-hospitalized participants falling below control levels sooner. Nearly all hospitalized and non-hospitalized participants maintained anti-RBD titers above controls for up to 12 months, suggesting longevity of protection against severe reinfections. Nonetheless, by 6 months, few participants retained >50% of their 1-month anti-N or anti-RBD titers. Vaccine-induced increases in anti-RBD titers were greater in non-hospitalized relative to hospitalized participants. Early convalescent antibody titers correlated with age, but no association was observed between Post-Acute Sequelae of SARS-CoV-2 infection (PASC) status or acute steroid treatment and convalescent antibody titers.

Interpretation

Hospitalized participants developed higher anti-SARS-CoV-2 antibody titers relative to non-hospitalized participants, a difference that persisted throughout 12 months, despite the faster decline in titers in hospitalized participants. In both groups, while anti-N titers fell below control levels for at least half of the participants, anti-RBD titers remained above control levels for almost all participants over 12 months, demonstrating generation of long-lived antibody responses known to correlate with protection from severe disease across COVID-19 severities. Overall, our findings contribute to the evolving understanding of COVID-19 antibody dynamics.

Funding

Austin Public Health, NIAAA, Babson Diagnostics, Dell Medical School Startup.

Both Humoral and Cellular Immune Responses to SARS-CoV-2 Are Essential to Prevent Infection: a Prospective Study in a Working Vaccinated Population from Southern France

COVID-19 vaccines have significantly decreased the number of severe cases of the disease, but the virus circulation remains important, and questions about the need of new vaccination campaigns remain unanswered. The individual's protection against SARS-CoV-2 infection is most commonly measured by the level and the neutralizing capacity of antibodies produced against SARS-CoV-2. T cell response is a major contributor in viral infection, and several studies have shown that cellular T cell response is crucial in fighting off SARS-CoV-2 infection. Actually, no threshold of protective immune response against SARS-CoV2 infection has been identified. To better understand SARS-CoV-2-mediated immunity, we assessed both B cell (measuring anti-Spike IgG titer and neutralization capacity) and T cell (measuring IFNγ release assay after specific SARS-CoV2 stimulation) responses to SARS-CoV-2 vaccination with or without virus encounter in a cohort of 367 working volunteers. Vaccinated individuals who had previously been infected had a stronger and more lasting immunity in comparison to vaccinated individuals naive to infection whose immunity started to decline 3 months after vaccination. IFNγ release ≥ 0.285 IU/mL and anti-Spike IgG antibodies ≥ 244 BAU/mL were associated with a sufficient immune response following vaccination preventing future infections. Individuals with comorbidities had a lower chance of reaching the protective thresholds of T cell and B cell responses as identified in multivariate analysis. A combined B cell and T cell analysis of immune responses to determine protective thresholds after SARS-CoV-2 vaccination will allow us to identify individuals in need of a booster vaccine dose, particularly in comorbid subjects.

Clinical Utility of SARS-CoV-2 Serological Testing and Defining a Correlate of Protection

Herein, we review established clinical use cases for SARS-CoV-2 antibody measures, which include diagnosis of recent prior infection, isolating high titer convalescent plasma, diagnosing multisystem inflammatory syndrome in children (MIS-C), and booster dosing in the immunosuppressed and other populations. We then address whether an antibody correlate of protection (CoP) for SARS-CoV-2 has been successfully defined with the following considerations: Antibody responses in the immunocompetent, vaccine type, variants, use of binding antibody tests vs. neutralization tests, and endpoint measures. In the transition from the COVID-19 pandemic to endemic, there has been much interest in defining an antibody CoP. Due to the high mutability of respiratory viruses and our current knowledge of SARS-CoV-2 variants defining a CoP for prevention of infection is unrealistic. However, a CoP may be defined for prevention of severe disease requiring hospitalization and/or death. Most SARS-CoV-2 CoP research has focused on neutralization measurements. However, there can be significant differences in neutralization test methods, and disparate responses to new variants depending on format. Furthermore, neutralization assays are often impractical for high throughput applications (e.g., assessing humoral immune response in populations or large cohorts). Nevertheless, CoP studies using neutralization measures are reviewed to determine where there is consensus. Alternatively, binding antibody tests could be used to define a CoP. Binding antibody assays tend to be highly automatable, high throughput, and therefore practical for large population applications. Again, we review studies for consensus on binding antibody responses to vaccines, focusing on standardized results. Binding antibodies directed against the S1 receptor binding domain (S1-RBD) of the viral spike protein can provide a practical, indirect measure of neutralization. Initially, a response for S1-RBD antibodies may be selected that reflects the peak response in immunocompetent populations and may serve as a target for booster dosing in the immunocompromised. From existing studies reporting peak S1-RBD responses in standardized units, an approximate range of 1372-2744 BAU/mL for mRNA and recombinant protein vaccines was extracted that could serve as an initial CoP target. This target would need to be confirmed and potentially adjusted for updated vaccines, and almost certainly for other vaccine formats (i.e., viral vector). Alternatively, a threshold or response could be defined based on outcomes over time (i.e., prevention of severe disease). We also discuss the precedent for clinical measurement of antibodies for vaccine-preventable diseases (e.g., hepatitis B). Lastly, cellular immunity is briefly addressed for its importance in the nature and durability of protection.

SARS-CoV-2 spike antigen-specific B cell and antibody responses in pre-vaccination period COVID-19 convalescent males and females with or without post-covid condition

Background

Following SARS-CoV-2 infection a significant proportion of convalescent individuals develop the post-COVID condition (PCC) that is characterized by wide spectrum of symptoms encompassing various organs. Even though the underlying pathophysiology of PCC is not known, detection of viral transcripts and antigens in tissues other than lungs raise the possibility that PCC may be a consequence of aberrant immune response to the viral antigens. To test this hypothesis, we evaluated B cell and antibody responses to the SARS-CoV-2 antigens in PCC patients who experienced mild COVID-19 disease during the pre-vaccination period of COVID-19 pandemic.

Methods

The study subjects included unvaccinated male and female subjects who developed PCC or not (No-PCC) after clearing RT-PCR confirmed mild COVID-19 infection. SARS-CoV-2 D614G and omicron RBD specific B cell subsets in peripheral circulation were assessed by flow cytometry. IgG, IgG3 and IgA antibody titers toward RBD, spike and nucleocapsid antigens in the plasma were evaluated by ELISA.

Results

The frequency of the B cells specific to D614G-RBD were comparable in convalescent groups with and without PCC in both males and females. Notably, in females with PCC, the anti-D614G RBD specific double negative (IgD-CD27-) B cells showed significant correlation with the number of symptoms at acute of infection. Anti-spike antibody responses were also higher at 3 months post-infection in females who developed PCC, but not in the male PCC group. On the other hand, the male PCC group also showed consistently high anti-RBD IgG responses compared to all other groups.

Conclusions

The antibody responses to the spike protein, but not the anti-RBD B cell responses diverge between convalescent males and females who develop PCC. Our findings also suggest that sex-related factors may also be involved in the development of PCC via modulating antibody responses to the SARS-CoV-2 antigens.

Ethno-demographic disparities in humoral responses to the COVID-19 vaccine among healthcare workers

The COVID-19 pandemic had a profound impact on global health, but rapid vaccine administration resulted in a significant decline in morbidity and mortality rates worldwide. In this study, we sought to explore the temporal changes in the humoral immune response against SARS-CoV-2 healthcare workers (HCWs) in Augusta, GA, USA, and investigate any potential associations with ethno-demographic features. Specifically, we aimed to compare the naturally infected individuals with naïve individuals to understand the immune response dynamics after SARS-CoV-2 vaccination. A total of 290 HCWs were included and assessed prospectively in this study. COVID status was determined using a saliva-based COVID assay. Neutralizing antibody (NAb) levels were quantified using a chemiluminescent immunoassay system, and IgG levels were measured using an enzyme-linked immunosorbent assay method. We examined the changes in antibody levels among participants using different statistical tests including logistic regression and multiple correspondence analysis. Our findings revealed a significant decline in NAb and IgG levels at 8-12 months postvaccination. Furthermore, a multivariable analysis indicated that this decline was more pronounced in White HCWs (odds ratio [OR] = 2.1, 95% confidence interval [CI] = 1.07-4.08, p = 0.02) and IgG (OR = 2.07, 95% CI = 1.04-4.11, p = 0.03) among the whole cohort. Booster doses significantly increased IgG and NAb levels, while a decline in antibody levels was observed in participants without booster doses at 12 months postvaccination. Our results highlight the importance of understanding the dynamics of immune response and the potential influence of demographic factors on waning immunity to SARS-CoV-2. In addition, our findings emphasize the value of booster doses to ensure durable immunity.

Impact of vaccine platform and BCG vaccination on antibody responses to COVID-19 vaccination

Multiple factors, including vaccine platform and prior vaccinations, influence vaccine responses. We compared antibody responses to CoronaVac (Sinovac) and ChAdOx1-S (AstraZeneca-Oxford) vaccination in 874 healthcare workers in Brazil. As participants were randomised to BCG vaccination or placebo in the preceding 0-6 months as part of the BCG vaccination to reduce the impact of COVID-19 in healthcare workers (BRACE) trial, we also investigated the influence of recent BCG vaccination on antibody responses to these COVID-19 vaccines. Twenty-eight days after the second dose of each vaccine, ChAdOx1-S induced a stronger anti-spike IgG response than CoronaVac vaccination. Recent BCG vaccination did not impact IgG antibody responses to ChAdOx1-S or CoronaVac.

Evaluation of Antibody Response and Adverse Effects following Heterologous COVID-19 Vaccine Booster with mRNA Vaccine among Healthcare Workers in Indonesia

Background: The administration of the third (or booster) dose of COVID-19 vaccine is important in maintaining protection against SARS-CoV-2 infection or the severity of the disease. In Indonesia, health care workers (HCWs) are among the first to receive a booster dose of the COVID-19 vaccine. In this study, we evaluated the antibody response and adverse events following heterologous booster vaccine using mRNA-1273 among HCWs that were fully vaccinated with inactivated viral vaccine as the priming doses. Methods: 75 HCWs at Dr. Soetomo General Hospital in Surabaya, Indonesia, participated in this study. The level of antibody against the SARS-CoV-2 receptor binding domain was analyzed at 1, 3, and 5 months following the second priming dose and at 1, 3, and 5 months after the booster dose. Results: We found a significantly higher level of antibody response in subjects receiving a booster dose of the mRNA-1273 vaccine compared to those receiving an inactivated viral vaccine as a booster. Interestingly, participants with hypertension and a history of diabetes mellitus showed a lower antibody response following the booster dose. There was a higher frequency of adverse events following injection with the mRNA-1273 vaccine compared to the inactivated viral vaccine, although the overall adverse events were considered minor. Conclusions: A heterologous booster dose using mRNA vaccine resulted in a high antibody response; however, participants with hypertension and diabetes mellitus displayed a lower antibody response.

Drug Cocktail Formulation via Circuit Design

Electronic circuits intuitively visualize and quantitatively simulate biological systems with nonlinear differential equations that exhibit complicated dynamics. Drug cocktail therapies are a powerful tool against diseases that exhibit such dynamics. We show that just six key states, which are represented in a feedback circuit, enable drug-cocktail formulation: 1) healthy cell number; 2) infected cell number; 3) extracellular pathogen number; 4) intracellular pathogenic molecule number; 5) innate immune system strength; and 6) adaptive immune system strength. To enable drug cocktail formulation, the model represents the effects of the drugs in the circuit. For example, a nonlinear feedback circuit model fits measured clinical data, represents cytokine storm and adaptive autoimmune behavior, and accounts for age, sex, and variant effects for SARS-CoV-2 with few free parameters. The latter circuit model provided three quantitative insights on the optimal timing and dosage of drug components in a cocktail: 1) antipathogenic drugs should be given early in the infection, but immunosuppressant timing involves a tradeoff between controlling pathogen load and mitigating inflammation; 2) both within and across-class combinations of drugs have synergistic effects; 3) if they are administered sufficiently early in the infection, anti-pathogenic drugs are more effective at mitigating autoimmune behavior than immunosuppressant drugs.

Serological response to vaccination in post-acute sequelae of COVID

BACKGROUND

Individuals with post-acute sequelae of COVID (PASC) may have a persistence in immune activation that differentiates them from individuals who have recovered from COVID without clinical sequelae. To investigate how humoral immune activation may vary in this regard, we compared patterns of vaccine-provoked serological response in patients with PASC compared to individuals recovered from prior COVID without PASC.

METHODS

We prospectively studied 245 adults clinically diagnosed with PASC and 86 adults successfully recovered from prior COVID. All participants had measures of humoral immunity to SARS-CoV-2 assayed before or after receiving their first-ever administration of COVID vaccination (either single-dose or two-dose regimen), including anti-spike (IgG-S and IgM-S) and anti-nucleocapsid (IgG-N) antibodies as well as IgG-S angiotensin-converting enzyme 2 (ACE2) binding levels. We used unadjusted and multivariable-adjusted regression analyses to examine the association of PASC compared to COVID-recovered status with post-vaccination measures of humoral immunity.

RESULTS

Individuals with PASC mounted consistently higher post-vaccination IgG-S antibody levels when compared to COVID-recovered (median log IgG-S 3.98 versus 3.74, P < 0.001), with similar results seen for ACE2 binding levels (median 99.1 versus 98.2, P = 0.044). The post-vaccination IgM-S response in PASC was attenuated but persistently unchanged over time (P = 0.33), compared to in COVID recovery wherein the IgM-S response expectedly decreased over time (P = 0.002). Findings remained consistent when accounting for demographic and clinical variables including indices of index infection severity and comorbidity burden.

CONCLUSION

We found evidence of aberrant immune response distinguishing PASC from recovered COVID. This aberrancy is marked by excess IgG-S activation and ACE2 binding along with findings consistent with a delayed or dysfunctional immunoglobulin class switching, all of which is unmasked by vaccine provocation. These results suggest that measures of aberrant immune response may offer promise as tools for diagnosing and distinguishing PASC from non-PASC phenotypes, in addition to serving as potential targets for intervention.

Association between Gut Microbiota and SARS-CoV-2 Infection and Vaccine Immunogenicity

Gut microbiota is increasingly recognized to play a pivotal role in various human physiological functions and diseases. Amidst the COVID-19 pandemic, research has suggested that dysbiosis of the gut microbiota is also involved in the development and severity of COVID-19 symptoms by regulating SARS-CoV-2 entry and modulating inflammation. Previous studies have also suggested that gut microbiota and their metabolites could have immunomodulatory effects on vaccine immunogenicity, including influenza vaccines and oral rotavirus vaccines. In light of these observations, it is possible that gut microbiota plays a role in influencing the immune responses to COVID-19 vaccinations via similar mechanisms including effects of lipopolysaccharides, flagellin, peptidoglycan, and short-chain fatty acids. In this review, we give an overview of the current understanding on the role of the gut microbiota in COVID-19 manifestations and vaccine immunogenicity. We then discuss the limitations of currently published studies on the associations between gut microbiota and COVID-19 vaccine outcomes. Future research directions shall be focused on the development of microbiota-based interventions on improving immune response to SARS-CoV-2 infection and vaccinations.

Differences in BNT126b2 and ChAdOx1 Homologous Vaccination Antibody Response among Teachers in Poznan, Poland

Children are among the best vectors to spread respiratory viruses, including emerging variants of SARS-CoV-2 due to the asymptomatic or relatively mild course of infection and simultaneously high titres of pathogens in the respiratory tract. Therefore, individuals who have constant contact with children, e.g., teachers should be vaccinated against COVID-19 as essential workers within the first phases of a vaccination campaign. In Poland, primary and secondary school teachers were vaccinated with ChAdOx1 from February 2021 with a three month interval between the two doses, while lecturers at medical universities, who are simultaneously healthcare workers, received the BNT126b2 vaccine from December 2020 with three weeks between the first and second doses. The aim of this study was to compare the antibody responses at two weeks and three months after vaccination and to estimate the vaccine effectiveness against COVID-19 among infection-naïve teachers vaccinated with mRNA and a vector vaccine. We found that the anti-SARS-CoV-2 spike protein antibodies were significantly higher among the lecturers but antibody waning was slower among the schoolteachers. However, those vaccinated with ChAdOx1 complained significantly more often of vaccine side effects. In addition, during the three months after the second vaccine dose no study participants were infected with SARS-CoV-2. The BNT126b2 vaccine gave higher antibody titres in comparison with ChAdOx1 but protection against COVID-19 in both cases was similar. Moreover, we did not find any anti-SARS-CoV-2 nucleoprotein antibodies at two weeks as well as at three months after vaccination among the study participants, which shows a very high vaccine effectiveness in the occupational group with a high SARS-CoV-2-infection risk.

Awareness of SARS-CoV-2 Omicron Variant Infection Among Adults With Recent COVID-19 Seropositivity

IMPORTANCE

Some individuals who were infected by the SARS-CoV-2 Omicron variant may have been completely unaware of their infectious status while the virus was actively transmissible.

OBJECTIVE

To examine awareness of infectious status among individuals during the recent Omicron variant surge in a diverse and populous urban region of Los Angeles County.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study analyzed the records of adult employees and patients of an academic medical center who were enrolled in a longitudinal COVID-19 serological study in Los Angeles County, California. These participants had 2 or more serial anti-nucleocapsid IgG (IgG-N) antibody measurements at least 1 month apart, with the first occurring after the end of a regional Delta variant surge (September 15, 2021) and a subsequent one occurring after the start of a regional Omicron variant surge (December 15, 2021). Adults with evidence of new SARS-CoV-2 infection occurring during the Omicron variant surge period through May 4, 2022, were included in the present study sample.

EXPOSURES

Recent Omicron variant infection as evidenced by SARS-CoV-2 seroconversion.

MAIN OUTCOMES AND MEASURES

Awareness of recent SARS-CoV-2 infection was ascertained from review of self-reported health updates, medical records, and COVID-19 testing data.

RESULTS

Of the 210 participants (median [range] age, 51 (23-84) years; 136 women [65%]) with serological evidence of recent Omicron variant infection, 44% (92) demonstrated awareness of any recent Omicron variant infection and 56% (118) reported being unaware of their infectious status. Among those who were unaware, 10% (12 of 118) reported having had any symptoms, which they attributed to a common cold or other non-SARS-CoV-2 infection. In multivariable analyses that accounted for demographic and clinical characteristics, participants who were health care employees of the medical center were more likely than nonemployees to be aware of their recent Omicron variant infection (adjusted odds ratio, 2.46; 95% CI, 1.30-4.65).

CONCLUSIONS AND RELEVANCE

Results of this study suggest that more than half of adults with recent Omicron variant infection were unaware of their infectious status and that awareness was higher among health care employees than nonemployees, yet still low overall. Unawareness may be a highly prevalent factor associated with rapid person-to-person transmission within communities.