SARS-CoV-2 Antibody Responses in Infection-Naive or Previously Infected Individuals After 1 and 2 Doses of the BNT162b2 Vaccine

Efficacy of a bivalent (D614 + B.1.351) SARS-CoV-2 recombinant protein vaccine with AS03 adjuvant in adults: a phase 3, parallel, randomised, modified double-blind, placebo-controlled trial

BACKGROUND

COVID-19 vaccines with alternative strain compositions are needed to provide broad protection against newly emergent SARS-CoV-2 variants of concern. This study aimed to describe the clinical efficacy and safety of a bivalent SARS-CoV-2 recombinant protein vaccine as a two-injection primary series during a period of circulation of the omicron (B.1.1.529) variant.

METHODS

We conducted a phase 3, parallel, randomised, modified double-blind, placebo-controlled trial in adults aged 18 years or older at 54 clinical research centres in eight countries (Colombia, Ghana, India, Kenya, Mexico, Nepal, Uganda, and Ukraine). Participants were recruited from the community and randomly assigned (1:1) by use of an interactive response technology system to receive two intramuscular 0·5 mL injections, 21 days apart, of the bivalent vaccine (5 μg of ancestral [D614] and 5 μg of beta [B.1.351] variant spike protein, with AS03 adjuvant) or placebo (0·9% normal saline). All participants, outcome assessors, and laboratory staff performing assays were masked to group assignments; those involved in the preparation and administration of the vaccines were unmasked. Participants were stratified by age (18-59 years and ≥60 years) and baseline SARS-CoV-2 rapid serodiagnostic test positivity. Symptomatic COVID-19 was defined as laboratory-confirmed (via nucleic acid amplification test or PCR test) COVID-19 with COVID-19-like illness symptoms. The primary efficacy endpoint was the clinical efficacy of the bivalent vaccine for prevention of symptomatic COVID-19 at least 14 days after the second injection (dose 2). Safety was assessed in all participants receiving at least one injection of the study vaccine or placebo. This trial is registered with ClinicalTrials.gov (NCT04904549) and is closed to recruitment.

FINDINGS

Between Oct 19, 2021, and Feb 15, 2022, 13 002 participants were enrolled and randomly assigned to receive the first dose of the study vaccine (n=6512) or placebo (n=6490). 12 924 participants (6472 in the vaccine group and 6452 in the placebo group) received at least one study injection, of whom 7542 (58·4%) were male and 9693 (75·0%) were SARS-CoV-2 non-naive. Of these 12 924 participants, 11 543 (89·3%) received both study injections (5788 in the vaccine group and 5755 in the placebo group). The efficacy-evaluable population after dose 2 comprised 11 416 participants (5736 in the vaccine group and 5680 in the placebo group). The median duration of follow-up was 85 days (IQR 50-95) after dose 1 and 58 days (29-70) after dose 2. 121 symptomatic COVID-19 cases were reported at least 14 days after dose 2 (32 in the vaccine group and 89 in the placebo group), with an overall vaccine efficacy of 64·7% (95% CI 46·6 to 77·2). Vaccine efficacy against symptomatic COVID-19 was 75·1% (95% CI 56·3 to 86·6) in SARS-CoV-2 non-naive participants and 30·9% (-39·3 to 66·7) in SARS-CoV-2-naive participants. Viral genome sequencing identified the infecting strain in 68 (56·2%) of 121 cases (omicron [BA.1 and BA.2] in 63; delta in four; and both omicron and delta in one). Immediate unsolicited adverse events were reported by four (<0·1%) participants in the vaccine group and seven (0·1%) participants in the placebo group. Immediate unsolicited adverse reactions within 30 min after any injection were reported by four (<0·1%) participants in the vaccine group and six (<0·1%) participants in the placebo group. In the reactogenicity subset with available data, solicited reactions (solicited injection-site reactions and solicited systemic reactions) within 7 days after any injection occurred in 1398 (57·8%) of 2420 vaccine recipients and 983 (40·9%) of 2403 placebo recipients. Grade 3 solicited reactions were reported by 196 (8·1%; 95% CI 7·0 to 9·3) of 2420 vaccine recipients and 118 (4·9%; 4·1 to 5·9) of 2403 placebo recipients within 7 days after any injection, with comparable frequencies after dose 1 and dose 2 in the vaccine group. At least one serious adverse event occurred in 30 (0·5%) participants in the vaccine group and 26 (0·4%) in the placebo group. The proportion of adverse events of special interest and deaths was less than 0·1% in both study groups. No adverse event of special interest, serious adverse event, or death was deemed to be treatment related. There were no reported cases of thrombosis with thrombocytopenia syndrome, myocarditis, pericarditis, Bell's Palsy, or Guillain-Barré syndrome, or other immune-mediated diseases.

INTERPRETATION

The bivalent variant vaccine conferred heterologous protection against symptomatic SARS-CoV-2 infection in the epidemiological context of the circulating contemporary omicron variant. These findings suggest that vaccines developed with an antigen from a non-predominant strain could confer cross-protection against newly emergent SARS-CoV-2 variants, although further investigation is warranted.

FUNDING

Sanofi, US Biomedical Advanced Research and Development Authority, and the US National Institute of Allergy and Infectious Diseases.

Robust immunogenicity of a third BNT162b2 vaccination against SARS-CoV-2 Omicron variant in a naïve New Zealand cohort

The ability of a third dose of the Pfizer-BioNTech BNT162b2 SARS-CoV-2 vaccine to stimulate immune responses against subvariants, including Omicron BA.1, has not been assessed in New Zealand populations. Unlike many overseas populations, New Zealanders were largely infection naïve at the time they were boosted. This adult cohort of 298 participants, oversampled for at-risk populations, was composed of 29% Māori and 28% Pacific peoples, with 40% of the population aged 55+. A significant proportion of the cohort was obese and presented with at least one comorbidity. Sera were collected 28 days and 6 months post second vaccination and 28 days post third vaccination. SARS-CoV-2 anti-S IgG titres and neutralising capacity using surrogate viral neutralisation assays against variants of concern, including Omicron BA.1, were investigated. The incidence of SARS-CoV-2 infection, within our cohort, prior to third vaccination was very low (<6%). This study found a third vaccine significantly increased the mean SARS-CoV-2 anti-S IgG titres, for every demographic subgroup, by a minimum of 1.5-fold compared to titres after two doses. Diabetic participants experienced a greater increase (∼4-fold) in antibody titres after their third vaccination, compared to non-diabetics (increase of ∼ 2-fold). This corrected for the deficiency in antibody titres within diabetic participants which was observed following two doses. A third dose also induced a neutralising response against Omicron variant BA.1, which was absent after two doses. This neutralising response improved regardless of age, BMI, ethnicity, or diabetes status. Participants aged ≥75 years consistently had the lowest SARS-CoV-2 anti-S IgG titres at each timepoint, however experienced the greatest improvement after three doses compared to younger participants. This study shows that in the absence of prior SARS-CoV-2 infection, a third Pfizer-BioNTech BNT162b2 vaccine enhances immunogenicity, including against Omicron BA.1, in a cohort representative of at-risk groups in the adult New Zealand population.

Impact of aging on immunity in the context of COVID-19, HIV, and tuberculosis

Knowledge of aging biology needs to be expanded due to the continuously growing number of elderly people worldwide. Aging induces changes that affect all systems of the body. The risk of cardiovascular disease and cancer increases with age. In particular, the age-induced adaptation of the immune system causes a greater susceptibility to infections and contributes to the inability to control pathogen growth and immune-mediated tissue damage. Since the impact of aging on immune function, is still to be fully elucidated, this review addresses some of the recent understanding of age-related changes affecting key components of immunity. The emphasis is on immunosenescence and inflammaging that are impacted by common infectious diseases that are characterized by a high mortality, and includes COVID-19, HIV and tuberculosis.

Evaluation of residual humoral immune response against SARS-CoV-2 by a surrogate virus neutralization test (sVNT) 9 months after BNT162b2 primary vaccination

The humoral response to SARS-CoV-2 vaccination has shown to be temporary, although may be more prolonged in vaccinated individuals with a history of natural infection. We aimed to study the residual humoral response and the correlation between anti-Receptor Binding Domain (RBD) IgG levels and antibody neutralizing capacity in a population of health care workers (HCWs) after 9 months from COVID-19 vaccination. In this cross-sectional study, plasma samples were screened for anti-RBD IgG using a quantitative method. The neutralizing capacity for each sample was estimated by means of a surrogate virus neutralizing test (sVNT) and results expressed as the percentage of inhibition (%IH) of the interaction between RBD and the angiotensin-converting enzyme. Samples of 274 HCWs (227 SARS-CoV-2 naïve and 47 SARS-CoV-2 experienced) were tested. The median level of anti-RBD IgG was significantly higher in SARS-CoV-2 experienced than in naïve HCWs: 2673.2 AU/mL versus 610.9 AU/mL, respectively (p <0.001). Samples of SARS-CoV-2 experienced subjects also showed higher neutralizing capacity as compared to naïve subjects: median %IH = 81.20% versus 38.55%, respectively; p <0.001. A quantitative correlation between anti-RBD Ab and inhibition activity levels was observed (Spearman's rho = 0.89, p <0.001): the optimal cut-off correlating with high neutralization was estimated to be 1236.1 AU/mL (sensitivity 96.8%, specificity 91.9%; AUC 0.979). Anti-SARS-CoV-2 hybrid immunity elicited by a combination of vaccination and infection confers higher anti-RBD IgG levels and higher neutralizing capacity than vaccination alone, likely providing better protection against COVID-19.

[Survey of spike-specific immunoglobulin G antibodies at approximately 3 months and 9 months after vaccination against coronavirus disease 2019 (severe acute respiratory syndrome coronavirus-2 [SARS-CoV-2]) in health care workers]

OBJECTIVE

We investigated the antibody titer of spike-specific immunoglobulin G (IgG) antibodies after receiving coronavirus repair uridine ribonucleic acid (RNA) vaccine (BNT162b2, Pfizer) in health care workers.

METHODS

At one hospital, health care workers received the vaccination between February and May 2021. A survey using questionnaires and spike-specific IgG antibody tests (Abbott) was conducted in 293 participants who had been vaccinated at least once and consented to this study at the time of medical checkups between April and May 2021. We calculated the antibody titer in each age group and days post-vaccination. We examined whether antibody titers of 4,000 AU/mL or higher (probability of high titer: approximately 95%, Abbott) were associated with adverse reactions after vaccination. In addition (1), the antibody titers at approximately 100 days after the second vaccination in 11 participants were remeasured. Furthermore (2), the antibody titers at approximately 260 days after the second vaccination in 13 participants were remeasured and compared with the initial measurements.

RESULTS

Of the participants, 276 were post-2 doses (A), 14 were post-1 dose (B), and 3 discontinued the second vaccination (C) at the time of health checkup. The median antibody titer was 11,045.8 AU/mL (50.7-40,000) in group A, 122.7 AU/mL (2.6-1,127.0) in group B, 27,099.3 AU/mL in one of group C who had recovered from coronavirus disease 2019 (COVID-19), and 574.2 AU/mL (283.3 and 865.1) in the other two of group C. The median antibody titer was the highest in those in their 20s, and there was a significant difference between those under and above 40 years of age. The median titer was the highest in 2 weeks to 1 month after the second vaccination. After the second dose, fatigue (≥ moderate) was associated with antibody titers of 4,000 AU/mL or higher. The antibody titers of 11 and 13 participants at approximately 100 and 260 days after the second vaccination were significantly lower than those at the first measurement, with median values of 2,838.0 AU/mL (832.9-5,698.6) and 512.0 AU/mL (154.0-1,220.0), respectively.

CONCLUSIONS

Antibody titers were higher in participants under 40 years of age than those 40 years or older. In addition, the percentage of high antibody titer (≧ 4,000 AU/mL) was higher in those who had severe fatigue after the second vaccination. The peak of antibody titer after the second dose was approximately 1 month, and the titer may decline gradually.

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.

Performance evaluation of the Ortho VITROS SARS-CoV-2 Spike-Specific Quantitative IgG test by comparison with the surrogate virus neutralizing antibody test and clinical assessment

BACKGROUND

Despite the worldwide campaigns of COVID-19 vaccinations, the pandemic is still a major medical and social problem. The Ortho VITROS SARS-CoV-2 spike-specific quantitative IgG (VITROS S-IgG) assay has been developed to assess neutralizing antibody (NT antibody) against SARS-CoV-2 spike (S) antibodies. However, it has not been evaluated in Japan, where the total cases and death toll are lower than the rest of the world.

METHODS

The clinical performance of VITROS S-IgG was evaluated by comparing with the NT antibody levels measured by the surrogate virus neutralizing antibody test (sVNT). A total of 332 serum samples from 188 individuals were used. Of these, 219 samples were from 75 COVID-19 patients: 96 samples from 20 severe/critical cases (Group S), and 123 samples from 55 mild/moderate cases (Group M). The remaining 113 samples were from 113 healthcare workers who had received 2 doses of the BNT162b2 vaccine.

RESULTS

VITROS S-IgG showed good correlation with the cPass sVNT assay (Spearman rho = 0.91). Both VITROS S-IgG and cPass sVNT showed significantly higher plateau levels of antibodies in Group S compared to Group M. Regarding the humoral immune responses after BNT162b2 vaccination, individuals who were negative for SARS-CoV-2 nucleocapsid (N)-specific antibodies had statistically lower titers of both S-IgG and sVNT compared to individuals with a history of COVID-19 and individuals who were positive for N-specific antibodies without history of COVID-19. In individuals who were positive for N-specific antibodies, S-IgG and sVNT titers were similar to individuals with a history of COVID-19.

CONCLUSIONS

Although the automated quantitative immunoassay VITROS S-IgG showed a reasonable correlation with sVNT antibodies, there is some discrepancy between Vitros S-IgG and cPass sVNT in milder cases. Thus, VITROS S-IgG can be a useful diagnostic tool in assessing the immune responses to vaccination and herd immunity. However, careful analysis is necessary to interpret the results.

Long-term adaptive response in COVID-19 vaccine recipients and the effect of a booster dose

We examined the immune response in subjects previously infected with SARS-CoV2 and infection-naïve 9 months after primary 2-dose COVID-19 mRNA vaccination and 3 months after the booster dose in a longitudinal cohort of healthcare workers. Nine months after primary vaccination, previously infected subjects exhibited higher residual antibody levels, with significant neutralizing activity against distinct variants compared to infection-naïve subjects. The higher humoral response was associated with higher levels of receptor binding domain (RBD)-specific IgG⁺ and IgA⁺ memory B cells. The booster dose increased neither neutralizing activity, nor the B and T cell frequencies. Conversely, infection-naïve subjects needed the booster to achieve comparable levels of neutralizing antibodies as those found in previously infected subjects after primary vaccination. The neutralizing titer correlated with anti-RBD IFNγ producing T cells, in the face of sustained B cell response. Notably, pre-pandemic samples showed high Omicron cross-reactivity. These data show the importance of the booster dose in reinforcing immunological memory and increasing circulating antibodies in infection-naïve subjects.

mRNA vaccine-a desirable therapeutic strategy for surmounting COVID-19 pandemic

As an acute respiratory infectious disease, COVID-19 threatens the safety of global public health. Given the current lack of specific treatment against this disease, research and development of vaccines have become sharp weapons for overcoming the pandemic. mRNA vaccines have become the lead in COVID-19 vaccination strategies due to their advantages, such as rapid industrial production and efficacy. A total of 137 COVID-19 vaccines have entered the clinical trial stage, among which 23 are mRNA vaccines, accounting for 17% of the total vaccines. Herein, we summarize the research and developmental processes of mRNA vaccines as well as the approach for protecting the human body against infection. Focusing on the latest clinical trial data of two COVID-19 mRNA vaccines from Pfizer and Modena, we discuss their effectiveness and safety. Finally, we analyze the challenges and problems that mRNA vaccines face in controlling the COVID-19 pandemic.

SARS-CoV-2-Neutralizing Humoral IgA Response Occurs Earlier but Is Modest and Diminishes Faster than IgG Response

Secretory immunoglobulin A (IgA) plays a crucial role in mucosal immunity for preventing the invasion of exogenous antigens; however, little is understood about the neutralizing activity of serum IgA. Here, to examine the role of IgA antibodies against COVID-19 illnesses, we determined the neutralizing activity of serum/plasma IgG and IgA purified from previously SARS-CoV-2-infected and COVID-19 mRNA vaccine-receiving individuals. We found that serum/plasma IgA possesses substantial but rather modest neutralizing activity against SARS-CoV-2 compared to IgG with no significant correlation with the disease severity. Neutralizing IgA and IgG antibodies achieved the greatest activity at approximately 25 and 35 days after symptom onset, respectively. However, neutralizing IgA activity quickly diminished to below the detection limit approximately 70 days after onset, while substantial IgG activity was observed until 200 days after onset. The total neutralizing activity in sera/plasmas of those with COVID-19 largely correlated with those in purified IgG and purified IgA and levels of anti-SARS-CoV-2-S1-binding IgG and anti-SARS-CoV-2-S1-binding IgA. In individuals who were previously infected with SARS-CoV-2 but had no detectable neutralizing IgA activity, a single dose of BNT162b2 or mRNA-1273 elicited potent serum/plasma-neutralizing IgA activity, but the second dose did not further strengthen the neutralization antibody response. The present data show that the systemic immune stimulation with natural infection and COVID-19 mRNA-vaccines elicits both SARS-CoV-2-specific neutralizing IgG and IgA responses in serum, but the IgA response is modest and diminishes faster than the IgG response. IMPORTANCE Secretory dimeric immunoglobulin A (IgA) plays an important role in preventing the invasion of foreign objects by its neutralizing activity on mucosal surfaces, while monomeric serum IgA is thought to relate to the phagocytic immune system activation. Here, we report that individuals with the novel coronavirus disease (COVID-19) developed both systemic neutralizing IgG (nIgG) and IgA (nIgA) active against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although the nIgA response was quick and reached the highest activity earlier than the nIgG response, nIgA activity was modest and diminished faster than nIgG activity. In individuals who recovered from COVID-19 but had no detectable nIgA activity, a single dose of COVID-19 mRNA vaccine elicited potent nIgA activity, but the second dose did not further strengthen the antibody response. Our study provides novel insights into the role and the kinetics of serum nIgA against the pathogen in both naturally infected and COVID-19 mRNA vaccine-receiving COVID-19-convalescent individuals.

Comparing hybrid and regular COVID-19 vaccine-induced immunity against the Omicron epidemic

Evidence on the effectiveness of COVID-19 vaccines among people who recovered from a previous SARS-CoV-2 infection is warranted to inform vaccination recommendations. Using the territory-wide public healthcare and vaccination records of over 2.5 million individuals in Hong Kong, we examined the potentially differential risk of SARS-CoV-2 infection, hospitalization, and mortality between those receiving two homologous doses of BNT162b2 or CoronaVac versus those with a previous infection receiving only one dose amid the Omicron epidemic. Results show a single dose after a SARS-CoV-2 infection is associated with a lower risk of infection (BNT162b2: adjusted incidence rate ratio [IRR] = 0.475, 95% CI: 0.410–0.550; CoronaVac: adjusted IRR = 0.397, 95% CI: 0.309–0.511) and no significant difference was detected in the risk of COVID-19-related hospitalization or mortality compared with a two-dose vaccination regimen. Findings support clinical recommendations that those with a previous infection could receive a single dose to gain at least similar protection as those who received two doses without a previous infection.

Eight Months of Serological Follow-Up of Anti-SARS-CoV-2 Antibodies in France: A Study among an Adult Population

BACKGROUND

Uncertainties remain regarding the nature and durability of the humoral immune response to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2).

AIM

This study investigated immunoglobulin G response and neutralizing activity to evaluate the mean antibody concentrations and response duration induced by each vaccination regimen in a French adult population.

METHODS

A study including blood sampling and questionnaires was carried out from November 2020 to July 2021 with three separate follow-up phases. Spike proteins and neutralizing antibodies were quantified using ELISA and a virus-neutralization test.

RESULTS

Overall, 295 participants were included. Seroprevalences were 11.5% (n = 34), 10.5% (n = 31), and 68.1% (n = 201) in phases 1, 2, and 3, respectively. Importantly, 5.8% (n = 17) of participants lost their natural antibodies. Antibody response of participants with only a prior infection was 88.2 BAU/mL, significantly lower than those vaccinated, which was 1909.3 BAU/mL (p = 0.04). Moreover, the antibody response of vaccinated participants with a prior infection was higher (3593.8 BAU/mL) than those vaccinated without prior infection (3402.9 BAU/mL) (p = 0.78). Vaccinated participants with or without prior infection had a higher seroneutralization rate (91.0%) than those unvaccinated with prior infection (65.0%).

CONCLUSION

These results demonstrated that single infection does not confer effective protection against SARS-CoV-2.

Correlation of Binding and Neutralizing Antibodies against SARS-CoV-2 Omicron Variant in Infection-Naïve and Convalescent BNT162b2 Recipients

In vaccine clinical trials, both binding antibody (bAb) levels and neutralization antibody (nAb) titers have been shown to be correlates of SARS-CoV-2 vaccine efficacy. We report a strong correlation bAb and nAb responses against the SARS-CoV-2 Omicron (BA.1) variant in infection-naïve and previously infected (convalescent) individuals after one and two doses of BNT162b2 vaccination. The vaccine-induced bAb levels against Omicron were significantly lower compared to previous variants of concern in both infection-naive and convalescent individuals, with the convalescent individuals showing significantly higher bAb compared to the naïve individuals at all timepoints. The finding that bAb highly correlated with nAb provides evidence for utilizing binding antibody assays as a surrogate for neutralizing antibody assays. Our data also revealed that after full vaccination, a higher percentage of individuals had undetectable Omicron nAb (58.6% in naive individuals, 7.4% in convalescent individuals) compared to the percentage of individuals who had negative Omicron bAb (0% in naive individuals, 0% in convalescent individuals). The discordance between bAb and nAb activities and the high degree of immune escape by Omicron may explain the high frequency of Omicron infections after vaccination.

Fully understanding the efficacy profile of the COVID-19 vaccination and its associated factors in multiple real-world settings

We performed a review study according to recent COVID-19 vaccines' real-world data to provide comparisons between COVID-19 vaccines regarding their relative efficacy. Although most vaccine platforms showed comparable effectiveness and efficacy, we highlight critical points and recent developments generated in studies that might affect vaccine efficacy including population-dependent effects of the vaccine (transplantation, adiposity, and specific comorbidities, as well as older age, male sex, ethnicity, and prior infection), vaccine type, variants of concern (VOC), and an extended vaccine schedule. Owing to these factors, community-based trials can be of great importance in determining vaccine effectiveness in a systematic manner; thus, uncertainty remains regarding vaccine efficacy. Long immune protection of vaccination with BNT162b2 or ChAdOx1 nCoV-19 has been demonstrated to be up to 61 months and 5-12 months after the previous infection, and boosting infection-acquired immunity for both the first and second doses of the BNT162b2 and ChAdOx1 nCoV-19 vaccines was correlated with high and durable protection. However, large cohort and longitudinal studies are required for the evaluation of immunity dynamics and longevity in unvaccinated, vaccinated, and infected individuals, as well as vaccinated convalescent individuals in real-world settings. Regarding the likelihood of vaccine escape variants evolving, an ongoing examination of the protection conferred against an evolving virus (new variant) by an extended schedule can be crucial.

Longitudinal Severe Acute Respiratory Syndrome Coronavirus 2 Vaccine Antibody Responses and Identification of Vaccine Breakthrough Infections Among Healthcare Workers Using Nucleocapsid Immunoglobulin G

BACKGROUND

Long-term studies of vaccine recipients are necessary to understand severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody durability and assess the impact of booster doses on antibody levels and protection from infection. The identification of vaccine breakthrough infections among fully vaccinated populations will be important in understanding vaccine efficacy and SARS-CoV-2 vaccine escape capacity.

METHODS

SARS-CoV-2 spike (S) receptor-binding domain and nucleocapsid (N) immunoglobulin (Ig) G levels were measured in a longitudinal study of 1000 Chicago healthcare workers who were infection naive or previously infected and then vaccinated. Changes in S and N IgG were followed up through 14 months, and vaccine breakthrough infections were identified by increasing levels of N IgG.

RESULTS

SARS-CoV-2 S IgG antibody levels among previously infected and previously noninfected individuals decreased steadily for 11 months after vaccination. Administration of a booster 8-11 months after vaccination increased S IgG levels >2-fold beyond those observed after 2 doses, resulting in S IgG levels that were indistinguishable between previously infected and uninfected individuals. Increases in N IgG identified vaccine breakthrough infections and showed >15% breakthrough infection rates during the Omicron wave starting in December 2021.

CONCLUSIONS

These results demonstrate SARS-CoV-2 antibody changes after vaccination and breakthrough infections and identify high levels of vaccine breakthrough infections during the Omicron wave, based on N IgG increases.

Age- and sex-based changes in spike protein antibody status after SARS-CoV-2 vaccination and effect of past-infection in healthcare workers in Osaka

Objective

We aimed to compare the changes in SARS-CoV-2 spike protein antibody titres based on age group and sex using paired blood sampling after vaccination in association with the presence of nucleocapsid protein antibody.

Methods

All participants were healthcare workers at Yao Municipal Hospital in Osaka who voluntarily provided peripheral blood samples (n = 636, men/women 151/485, mean age 45 years). We investigated the serial changes in SARS-CoV-2 spike protein antibody titres at 1 and 7 months after the second vaccination regarding their relationship with sex and age group. At 7 months, we also examined anti-nucleocapsid assays. Antibody titres were shown as logarithmic values and the differences were assessed using a paired or unpaired student’s t-test as appropriate.

Results

Among participants younger than 30 years, the antibody titres of spike protein were significantly higher in women one (p = 0.005) and seven (p = 0.038) months after vaccination. However, among those aged 30–49 years, the antibody titres were not different between the sexes at either follow-up time point. In contrast, among those aged 50–59 years, between-sex differences in antibody titres were observed only at 7 months, which was associated with a significant reduction in men. A significant negative correlation was observed between the antibody titres for spike protein at both time points in participants with positive nucleocapsid protein antibody at 7 months (r = − 0.467, p = 0.043), although a significant positive correlation was observed in those with negative results (r = 0.645, p < 0.001),

Conclusions

Between-sex differences in SARS-CoV-2 spike protein antibody titres by paired blood sampling at different time points after vaccination depended on age group. The presence of nucleocapsid protein antibody was associated with changes in spike protein antibody titres after vaccination.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07695-7.

Determinants of antibody response to severe acute respiratory syndrome coronavirus 2 mRNA vaccines in people with HIV

We identified determinants of SARS-CoV-2 mRNA vaccine antibody response in people with HIV (PWH). Antibody response was higher among PWH less than 60 years, with CD4+ cell count superior to 350 cells/μl and vaccinated with mRNA-1273 by Moderna compared with BNT162b2 by Pfizer-BioNTech. Preinfection with SARS-CoV-2 boosted the antibody response and smokers had an overall lower antibody response. Elderly PWH and those with low CD4+ cell count should be prioritized for booster vaccinations.

Effectiveness and protection duration of Covid-19 vaccines and previous infection against any SARS-CoV-2 infection in young adults

Data on effectiveness and protection duration of Covid-19 vaccines and previous infection against general SARS-CoV-2 infection in general populations are limited. Here we evaluate protection from Covid-19 vaccination (primary series) and previous infection in 21,261 university students undergoing repeated surveillance testing between 8/8/2021-12/04/2021, during which B.1.617 (delta) was the dominant SARS-CoV-2 variant. Estimated mRNA-1273, BNT162b2, and AD26.COV2.S effectiveness against any SARS-CoV-2 infection is 75.4% (95% CI: 70.5-79.5), 65.7% (95% CI: 61.1-69.8), and 42.8% (95% CI: 26.1-55.8), respectively. Among previously infected individuals, protection is 72.9% when unvaccinated (95% CI: 66.1-78.4) and increased by 22.1% with full vaccination (95% CI: 15.8-28.7). Statistically significant decline in protection is observed for mRNA-1273 (P < .001), BNT162b2 (P < .001), but not Ad26.CoV2.S (P = 0.40) or previous infection (P = 0.12). mRNA vaccine protection dropped 29.7% (95% CI: 17.9-41.6) six months post- vaccination, from 83.2% to 53.5%. We conclude that the 2-dose mRNA vaccine series initially offers strong protection against general SARS-CoV-2 infection caused by the delta variant in young adults, but protection substantially decreases over time. These findings indicate that vaccinated individuals may still contribute to community spread. While previous SARS-CoV-2 infection consistently provides moderately strong protection against repeat infection from delta, vaccination yields a substantial increase in protection.

Neutralizing Antibody Activity to SARS-CoV-2 Delta (B.1.617.2) and Omicron (B.1.1.529) After One and Two Doses of BNT162b2 Vaccine in Infection-Naïve and Previously-Infected Individuals

Previous reports demonstrated that severe acute respiratory syndrome coronavirus (SARS-CoV-2) binding immunoglobulin G levels did not increase significantly between the first and second doses of the BNT162b2 vaccine in previously infected individuals. We tested neutralizing antibodies (nAbs) against SARS-CoV-2 Delta and Omicron variants after the first and second doses of this vaccine in infection-naive and previously infected individuals. Delta, but not Omicron, nAb titers significantly increased from the first to the second dose in both groups of individuals. Importantly, we found that Omicron nAb titers were much lower than Delta nAb titers and that even after 2 doses of vaccine, 17 of 29 individuals in the infection-naive group and 2 of 27 in the previously infected group did not have detectable Omicron nAb titers. Infection history alone did not adequately predict whether a second dose resulted in adequate nAb. For future variants of concern, the discussion on the optimal number of vaccine doses should be based on studies testing for nAb against the specific variant.

SARS-CoV-2-neutralizing humoral IgA response occurs earlier but modest and diminishes faster compared to IgG response

Secretory immunoglobulin A (IgA) plays a crucial role in the mucosal immunity for preventing the invasion of the exogenous antigens, however, little has been understood about the neutralizing activity of serum IgA. Here, to examine the role of IgA antibodies against COVID-19 illnesses, we determined the neutralizing activity of serum/plasma IgG and IgA purified from previously SARS-CoV-2-infected and COVID-19 mRNA-vaccine-receiving individuals. We found that serum/plasma IgA possesses substantial but rather modest neutralizing activity against SARS-CoV-2 compared to IgG with no significant correlation with the disease severity. Neutralizing IgA and IgG antibodies achieved the greatest activity at approximately 25 and 35 days after symptom onset, respectively. However, neutralizing IgA activity quickly diminished and went down below the detection limit approximately 70 days after onset, while substantial IgG activity was observed till 200 days after onset. The total neutralizing activity in sera/plasmas of those with COVID-19 largely correlated with that in purified-IgG and purified-IgA and levels of anti-SARS-CoV-2-S1-binding IgG and anti-SARS-CoV-2-S1-binding IgA. In individuals who were previously infected with SARS-CoV-2 but had no detectable neutralizing IgA activity, a single dose of BNT162b2 or mRNA-1273 elicited potent serum/plasma neutralizing IgA activity but the second dose did not further strengthen the neutralization antibody response. The present data show that the systemic immune stimulation with natural infection and COVID-19 mRNA-vaccines elicit both SARS-CoV-2-specific neutralizing IgG and IgA response in serum, but the IgA response is modest and diminishes faster compared to IgG response.

Author Summary

Immunoglobulin A (IgA) is the most abundant type of antibody in the body mostly located on mucosal surfaces as a dimeric secretory IgA. Such secretory IgA plays an important role in preventing the adherence and invasions of foreign objects by its neutralizing activity, while monomeric serum IgA is thought to relate to the phagocytic immune system activation. Here, we report that individuals with the novel coronavirus disease (COVID-19) developed both systemic neutralizing IgG and IgA active against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although the neutralizing IgA response was quick and reached the highest activity 25 days post-symptom-onset, compared to 35 days for IgG response, neutralizing IgA activity was modest and diminished faster than neutralizing IgG response. In individuals, who recovered from COVID-19 but had no detectable neutralizing IgA activity, a single dose of COVID-19 mRNA-vaccine elicited potent neutralizing IgA activity but the second dose did not further strengthen the antibody response. Our study provides novel insights into the role and the kinetics of serum IgA against the viral pathogen both in naturally-infected and COVID-19 mRNA-vaccine-receiving COVID-19-convalescent individuals.

Humoral immunogenicity and tolerability of heterologous ChAd/BNT compared with homologous BNT/BNT and ChAd/ChAd SARS-CoV-2 vaccination in hemodialysis patients : A multicenter prospective observational study

BACKGROUND

After the reports of severe adverse reactions to the AstraZeneca ChAdOx1-S-nCoV-19 vaccine, patients who had received one dose of ChAdOx1-S-nCoV-19 vaccine were recommended a second dose of Pfizer's BNT162b2 vaccine. In hemodialysis patients, we compared the humoral immunogenicity and tolerability of homologous vaccination with ChAdOx1-nCoV-19/ChAdOx1-nCoV-19 (ChAd/ChAd) and BNT162b2/BNT162b2 (BNT/BNT) with heterologous vaccination of first dose of ChAdOx1-nCoV-19 and a second dose with BNT162b2 (ChAd/BNT).

METHODS

In a multicenter prospective observational study, SARS-CoV-2 spike-IgG antibody levels, Nucleocapsid-protein-IgG-antibodies, and vaccine tolerability were assessed 6 weeks after second SARS-CoV-2 vaccination in 137 hemodialysis patients and 24 immunocompetent medical personnel.

RESULTS

In COVID-19-naïve hemodialysis patients, significantly higher median SARS-CoV-2-spike IgG levels were found after ChAd/BNT (N = 16) compared to BNT/BNT (N = 100) or ChAd/ChAd (N = 10) (1744 [25th-75th percentile 276-2840] BAU/mL versus 361 [25th-75th percentile 120-936] BAU/mL; p = 0.009; 1744 [25th-75th percentile 276-2840] BAU/mL versus 100 [25th-75th percentile 41-346] BAU/mL; p = 0.017, respectively). Vaccinated, COVID-19-naïve medical personnel had median SARS-CoV-2 spike-IgG levels of 650 (25th-75th percentile 217-1402) BAU/mL and vaccinated hemodialysis patients with prior COVID-19 7047 (25th-75th percentile 685-10,794) BAU/mL (N = 11). In multivariable regression analysis, heterologous vaccination (ChAd/BNT) of COVID-19-naïve hemodialysis patients was independently associated with SARS-CoV-2 spike-IgG levels. The first dose of ChAd and the second dose of BNT after the first vaccination with ChAd (heterologous vaccination, ChAd/BNT) were associated with more frequent but manageable side effects compared with homologous BNT.

CONCLUSIONS

Within the limitations of this study, heterologous vaccination with ChAd/BNT appears to induce stronger humoral immunity and more frequent but manageable side effects than homologous vaccination with BNT/BNT or with ChAd/ChAd in COVID-19-naïve hemodialysis patients.

SARS-CoV-2 Receptor-Binding Domain IgG Response to AstraZeneca AZD1222 COVID-19 Vaccination, Jamaica

The Caribbean region is lacking an assessment of the antibody response and side effects experienced after AstraZeneca COVID-19 vaccination (AZD1222). We examined severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike receptor-binding domain (RBD) IgG levels and report the side effects noted in a Jamaican population after AZD1222 vaccination. Median RBD IgG levels for persons without evidence of previous SARS-CoV-2 infection were 43.1 binding international units (bIU)/mL 3 to 7 weeks after the first dose, increasing to 100.1 bIU/mL 3 to 7 weeks after the second dose, and decreasing to 46.9 bIU/mL 16 to 22 weeks after the second dose. The median RBD IgG level 2 to 8 weeks after symptom onset for unvaccinated SARS-CoV-2-infected persons of all disease severities was 411.6 bIU/mL. Common AZD1222 side effects after the first dose were injection site pain, headache, and chills. Most people reported no side effects after the second dose. AZD1222 is widely used across the English-speaking Caribbean, and our study provides evidence for its continued safe and effective use in vaccination programs.

Durability of Humoral Responses after the Second Dose of mRNA BNT162b2 Vaccine in Residents of a Long Term Care Facility

Residents of long-term care facilities (LTCFs) have been dramatically hit by the COVID-19 pandemic on a global scale as older age and comorbidities pose an increased risk of severe disease and death. The aim of the study was to assess the quantity and durability of specific antibody responses to SARS-CoV-2 after the first cycle (two doses) of BNT162b2 vaccine. To achieve this, SARS-CoV-2 Spike-specific IgG (S-IgG) titers was evaluated in 432 residents of the largest Italian LTCF at months 2 and 6 after vaccination. By stratifying levels of humoral responses as high, medium, low and null, we did not find any difference when comparing the two time points; however, the median levels of antibodies halved overtime. As positive nucleocapsid serology was associated with a reduced risk of a suboptimal response at both time points, we conducted separate analyses accordingly. In subjects with positive serology, the median level of anti-S IgG slightly increased at the second time point, while a significant reduction was observed in patients without previous exposure to the virus. At month 6, diabetes alone was associated with an increased risk of impaired response. Our data provide additional insights into the longitudinal dynamics of the immune response to BNT162b2 vaccination in the elderly, highlighting the need for SARS-CoV-2 antibody monitoring following third-dose administration.

Post vaccination analysis of anti-spike antibody responses in kidney transplant recipients with and without COVID-19 infection in a tertiary care center, India

Background

To investigate the anti-spike antibody response to vaccination in Kidney transplant recipients (KTRs) previously infected with SARS-CoV-2 as compared to KTRs with no history of COVID-19 from India.

Methods

SARS-CoV-2 spike immunoglobulin (Ig) G antibody response was measured in 105 post COVID-19 KTRs with PCR confirmed SARS-CoV-2 infection who received either no vaccination (cohort 1), single (cohort 2) or two doses (cohort 3) of vaccine and compared to 103 two-dose vaccinated COVID-19 naïve KTRs with no history of COVID-19 (cohort 4).

Results

Out of 103 COVID-19 naïve two-dose vaccinated KTRs, less than 50% became seropositive with anti-spike antibody titres &gt; 50AU/mL subsequent to complete vaccination, the seroconversion rate being comparable in subjects receiving CovishieldTM versus CovaxinTM vaccines. However, the seropositive KTRs vaccinated with CovishieldTM had higher anti-spike antibody titres as compared to those who received CovaxinTM. We observed higher anti-SARS-CoV-2 spike antibody levels in post COVID-19 KTRs after 1 dose of vaccine as compared with COVID-19 naïve two-dose vaccinated KTRs. Importantly, the second dose in post COVID-19 KTRs did not significantly increase anti-spike antibody levels compared with the single dose recipients.

Conclusions

Our data presents that in KTRs with previous SARS-CoV-2 infection a single dose of vaccine (CovishieldTM) may be effective in mounting optimal immune response. In contrast, COVID-19 naïve two-dose vaccinated KTRs respond poorly (&lt;50%) to current recommendation of a two-dose regimen in India.

SARS-CoV-2 Vaccine Antibody Response and Breakthrough Infection in Patients Receiving Dialysis

BACKGROUND

Whether breakthrough SARS-CoV-2 infections after vaccination are related to the level of postvaccine circulating antibody is unclear.

OBJECTIVE

To determine longitudinal antibody-based response and risk for breakthrough infection after SARS-CoV-2 vaccination.

DESIGN

Prospective study.

SETTING

Nationwide sample from dialysis facilities.

PATIENTS

4791 patients receiving dialysis.

MEASUREMENTS

Remainder plasma from a laboratory processing routine monthly tests was used to measure qualitative and semiquantitative antibodies to the receptor-binding domain (RBD) of SARS-CoV-2. To evaluate whether peak or prebreakthrough RBD values were associated with breakthrough infection, a nested case-control analysis matched each breakthrough case patient to 5 control patients by age, sex, and vaccination month and adjusted for diabetes status and region of residence.

RESULTS

Of the 4791 patients followed with monthly RBD assays, 2563 were vaccinated as of 14 September 2021. Among the vaccinated patients, the estimated proportion with an undetectable RBD response increased from 6.6% (95% CI, 5.5% to 7.8%) 14 to 30 days after vaccination to 20.2% (CI, 17.0% to 23.3%) 5 to 6 months after vaccination. Estimated median index values decreased from 91.9 (CI, 78.6 to 105.2) 14 to 30 days after vaccination to 8.4 (CI, 7.6 to 9.3) 5 to 6 months after vaccination. Breakthrough infections occurred in 56 patients, with samples collected a median of 21 days before breakthrough infection. Compared with prebreakthrough index RBD values of 23 or higher (equivalent to ≥506 binding antibody units per milliliter), prebreakthrough RBD values less than 10 and values from 10 to less than 23 were associated with higher odds for breakthrough infection (rate ratios, 11.6 [CI, 3.4 to 39.5] and 6.0 [CI, 1.5 to 23.6], respectively).

LIMITATIONS

Single measure of vaccine response; ascertainment of COVID-19 diagnosis from electronic health records.

CONCLUSION

The antibody response to SARS-CoV-2 vaccination wanes rapidly in persons receiving dialysis. In this population, the circulating antibody response is associated with risk for breakthrough infection.

PRIMARY FUNDING SOURCE

Ascend Clinical Laboratory.

Vaccination of COVID-19 Convalescent Plasma Donors Increases Binding and Neutralizing Antibodies Against SARS-CoV-2 Variants

Background

COVID‐19 convalescent plasma (CCP) was widely used as passive immunotherapy during the first waves of SARS‐CoV‐2 infection in the US. However, based on observational studies and randomized controlled trials, the beneficial effects of CCP were limited, and its use was virtually discontinued early in 2021, in concurrence with increased vaccination rates and availability of monoclonal antibody (mAb) therapeutics. Yet, as new variants of the SARS‐CoV‐2 spread, interest in CCP derived from vaccine‐boosted CCP donors is resurging. The effect of vaccination of previously infected CCP donors on antibodies against rapidly spreading variants is still under investigation.

Study design/methods

In this study, paired‐samples from 11 CCP donors collected before and after vaccination was tested to measure binding antibody levels and neutralization activity against the ancestral Wuhan‐Hu‐1 and SARS‐CoV‐2 variants (Wuhan‐Hu‐1 with D614G, alpha, beta, gamma, delta, epsilon) on the Ortho Vitros Spike Total Ig and IgG assays, the MSD V‐PLEX SARS‐CoV‐2 arrays for IgG binding and ACE2 inhibition, and variant‐specific Spike Reporter Viral Particle Neutralization (RVPN) assays.

Results/findings

Binding and neutralizing antibodies were significantly boosted by vaccination, with several logs higher neutralization for all the variants tested post‐vaccination compared to the pre‐vaccination samples, with no difference found among the individual variants.

Discussion

Vaccination of previously infected individuals boosts antibodies including neutralizing activity against all SARS‐CoV‐2 variants.

Humoral antibody kinetics with ChAdOx1-nCOV (Covishield™) and BBV-152 (Covaxin™) vaccine among Indian Healthcare workers: A 6-month longitudinal cross-sectional Coronavirus Vaccine-induced antibody titre (COVAT) study

BACKGROUND AND AIMS

There is limited data available on longitudinal humoral antibody dynamics following two doses of ChAdOx1-nCOV (Covishield™) and BBV-152 (Covaxin™) vaccine against SARS-CoV-2 among Indians.

METHODS

We conducted a 6-month longitudinal study in vaccinated healthcare workers by serially measuring quantitative anti-spike antibody at 3-weeks, 3-months and 6-months after the completion of second dose. Geometric mean titer (GMT) and linear mixed models were used to assess the dynamics of antibody levels at 6 months.

RESULTS

Of the 481 participants, GMT of anti-spike antibody decreased by 56% at 6-months regardless of age, gender, blood group, body-mass index and comorbidities in 360 SARS-CoV-2 naive individuals but significantly more in hypertensives. Participants with past infection had significantly higher GMT at all time points compared to the naive individuals. Among SARS-CoV-2 naive cohorts, a significantly higher GMT was noted amongst the Covishield recipients at all time points, but there was a 44% decline in GMT at 6-month compared to the peak titer period. Decline in GMT was insignificant (8%) in Covaxin recipients at 6-month despite a lower GMT at all time points vs. Covishield. There was 5.6-fold decrease in seropositivity rate at 6-month with both vaccines. Participants with type 2 diabetes mellitus have a lower seropositivity rate at all the time points. Seropositivity rate was significantly higher with Covishield vs. Covaxin at all time points except at 6-month where Covaxin recipients had a higher seropositivity rate but no difference noted in propensity-matched analysis.

CONCLUSIONS

There is waning humoral antibody response following two doses of either vaccine at six months. Covishield recipients had a higher anti-spike antibody GMT compared with Covaxin at all-time points, however a significant decline in antibody titers was seen with Covishield but not with Covaxin at 6-months.

Affinity of anti-spike antibodies in SARS-CoV-2 patient plasma and its effect on COVID-19 antibody assays

Background

Measuring anti-spike protein antibodies in human plasma or serum is commonly used to determine prior exposure to SARS-CoV-2 infection and to assess the anti-viral protection capacity. According to the mass-action law, a lesser concentration of tightly binding antibody can produce the same quantity of antibody-antigen complexes as higher concentrations of lower affinity antibody. Thus, measurements of antibody levels reflect both affinity and concentration. These two fundamental parameters cannot be disentangled in clinical immunoassays, and so produce a bias which depends on the assay format.

Methods

To determine the apparent affinity of anti-spike protein antibodies, a small number of antigen-coated magnetic microparticles were imaged by fluorescence microscopy after probing antigen-antibody equilibria directly in patient plasma. Direct and indirect anti-SARS-CoV-2 immunoassays were used to measure antibody levels in the blood of infected and immunised individuals.

Findings

We observed affinity maturation of antibodies in convalescent and vaccinated individuals, showing that higher affinities are achieved much faster by vaccination. We demonstrate that direct and indirect immunoassays for measuring anti-spike protein antibodies depend differently on antibody affinity which, in turn, affects accurate interpretation of the results.

Interpretation

Direct immunoassays show substantial antibody affinity dependence. This makes them useful for identifying past SARS-CoV-2 exposure. Indirect immunoassays provide more accurate quantifications of anti-viral antibody levels.

Funding

The authors are all full-time employees of Abbott Laboratories. Abbott Laboratories provided all operating funds. No external funding sources were used in this study.

Waning Immune Humoral Response to BNT162b2 Covid-19 Vaccine over 6 Months

BACKGROUND

Despite high vaccine coverage and effectiveness, the incidence of symptomatic infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been increasing in Israel. Whether the increasing incidence of infection is due to waning immunity after the receipt of two doses of the BNT162b2 vaccine is unclear.

METHODS

We conducted a 6-month longitudinal prospective study involving vaccinated health care workers who were tested monthly for the presence of anti-spike IgG and neutralizing antibodies. Linear mixed models were used to assess the dynamics of antibody levels and to determine predictors of antibody levels at 6 months.

RESULTS

The study included 4868 participants, with 3808 being included in the linear mixed-model analyses. The level of IgG antibodies decreased at a consistent rate, whereas the neutralizing antibody level decreased rapidly for the first 3 months with a relatively slow decrease thereafter. Although IgG antibody levels were highly correlated with neutralizing antibody titers (Spearman's rank correlation between 0.68 and 0.75), the regression relationship between the IgG and neutralizing antibody levels depended on the time since receipt of the second vaccine dose. Six months after receipt of the second dose, neutralizing antibody titers were substantially lower among men than among women (ratio of means, 0.64; 95% confidence interval [CI], 0.55 to 0.75), lower among persons 65 years of age or older than among those 18 to less than 45 years of age (ratio of means, 0.58; 95% CI, 0.48 to 0.70), and lower among participants with immunosuppression than among those without immunosuppression (ratio of means, 0.30; 95% CI, 0.20 to 0.46).

CONCLUSIONS

Six months after receipt of the second dose of the BNT162b2 vaccine, humoral response was substantially decreased, especially among men, among persons 65 years of age or older, and among persons with immunosuppression.

SARS-CoV-2 neutralizing antibodies after one or two doses of Comirnaty (BNT162b2, BioNTech/Pfizer): Kinetics and comparison with chemiluminescent assays

BACKGROUND

Studies evaluating neutralizing antibody (NAb) after BNT162b2 vaccine are scarce. We therefore compared NAb using the plaque reduction neutralization test (PRNT) in vaccinated subjects, with those from five chemiluminescent (CLIA) assays, two targeting ACE and S-RBD interaction.

METHODS

Sera from 174 completely Comirnaty/BNT162b2 vaccinated healthcare workers (HCW) were evaluated at t₁₂ and t₂₈. NAb titers at low (PRNT₅₀) or high (PRNT₉₀) stringency were compared with: Liaison SARS-CoV-2 Trimeric-S IgG, Elecsys S-RBD Ab, Maglumi SARS-CoV-2 S-RBD IgG and SARS-CoV-2 Nab; iFlash 2019-nCoV NAb.

RESULTS

Neither PRNT₅₀ nor PRNT₉₀ correlated with age (range, 24-65 years); no significant differences were found for gender. PRNT₅₀ and PRNT₉₀ seropositive titers (≥1:20) were 43 (24.7%) and 15 (8.6%) at t₁₂ and 167 (95.9%) and 149 (85.6%) at t₂₈. CLIA results at t₂₈ were uncorrelated with age, apart from Elecsys S-RBD Ab (r = -0.164, p = 0.046). Gender differences were found for Maglumi SARS-CoV-2 S-RBD IgG (p = 0.037) and Maglumi NAb (p = 0.046). Considering PRNT₅₀ at thresholds of 1:20 (or 1:40) and 1:160 (or 1:320), corresponding to different immune protective levels, CLIA cut-offs have been identified.

CONCLUSIONS

Comirnaty/BNT162b2 elicits strong NAb production, especially 28 days after first inoculum. Differences in correlation between Nab titers and circulating antibodies measured by 5 immunoassays have been found, being stronger the correlation for Maglumi Nab.

SARS-CoV-2 vaccine antibody response and breakthrough infection in dialysis

BACKGROUND

Patients receiving dialysis are a sentinel population for groups at high risk for death and disability from COVID-19. Understanding correlates of protection post-vaccination can inform immunization and mitigation strategies.

METHODS

Monthly since January 2021, we tested plasma from 4791 patients receiving dialysis for antibodies to the receptor-binding domain (RBD) of SARS-CoV-2 using a high-throughput assay. We qualitatively assessed the proportion without a detectable RBD response and among those with a response, semiquantitative median IgG index values. Using a nested case-control design, we matched each breakthrough case to five controls by age, sex, and vaccination-month to determine whether peak and pre-breakthrough RBD IgG index values were associated with risk for infection post-vaccination.

RESULTS

Among 2563 vaccinated patients, the proportion without a detectable RBD response increased from 6.6% [95% CI 5.5-8.1] in 14-30 days post-vaccination to 20.2% [95% CI 17.1-23.8], and median index values declined from 92.7 (95% CI 77.8-107.5) to 3.7 (95% CI 3.1-4.3) after 5 months. Persons with SARS-CoV-2 infection prior-to-vaccination had higher peak index values than persons without prior infection, but values equalized by 5 months (p=0.230). Breakthrough infections occurred in 56 patients, with samples collected a median of 21 days pre-breakthrough. Peak and pre-breakthrough RBD values <23 (equivalent to <506 WHO BAU/mL) were associated with higher odds for breakthrough infection (OR: 3.7 [95% CI 2.0-6.8] and 9.8 [95% CI 2.9-32.8], respectively).

CONCLUSIONS

The antibody response to SARS-CoV-2 vaccination wanes rapidly, and in persons receiving dialysis, the persisting antibody response is associated with risk for breakthrough infection.