Clinical validation of the Siemens quantitative SARS-CoV-2 spike IgG assay (sCOVG) reveals improved sensitivity and a good correlation with virus neutralization titers

Comparative study between virus neutralisation testing and other serological methods detecting anti-SARS-CoV-2 antibodies in Europe, 2021

One consequence of the ongoing coronavirus disease pandemic was the rapid development of both in-house and commercial serological assays detecting anti-SARS-CoV-2 antibodies, in an effort to reliably detect acute and past SARS-CoV-2 infections. It is crucial to evaluate the quality of these serological tests and consequently the sero-epidemiological studies that are performed with the respective tests. Here, we describe the set-up and results of a comparative study, in which a laboratory contracted by the European Centre for Disease Prevention and Control offered a centralised service to EU/EEA Member and pre-accession Member States to test representative serum specimens with known serological results, with the gold standard technique (virus neutralisation tests) to determine the presence of neutralising antibodies. Laboratories from 12 European countries shared 719 serum specimens with the contractor laboratory. We found that in-house serological tests detecting neutralising antibodies showed the highest percent agreement, both positive and negative, with the virus neutralisation test results. Despite extensive differences in virus neutralisation protocols neutralisation titres showed a strong correlation. From the commercial assays, the best positive percent agreement was found for SARS-CoV-2 IgG (sCOVG) (Siemens - Atellica IM Analyzer). Despite lower positive percent agreement of LIAISON SARS-CoV-2 TrimericS IgG kit (Diasorin Inc.), the obtained results showed relatively good correlation with neutralisation titres. The set-up of this study allowed for high comparability between laboratories and enabled laboratories that do not have the capacity or capability to perform VNTs themselves. Given the variety of in-house protocols detecting SARS-CoV-2 specific neutralising antibodies, including the virus strain, it could be of interest to select reference isolates for SARS-CoV-2 diagnostic to be made available for interested EU Member States and pre-accession countries.

Trajectory analyses to identify persistently low responders to COVID-19 vaccination in patients with inflammatory bowel disease: a prospective multicentre controlled study, J-COMBAT

BACKGROUND

The degree of immune response to COVID-19 vaccination in inflammatory bowel disease (IBD) patients based on actual changes in anti-SARS-CoV-2 antibody titres over time is unknown.

METHODS

Data were prospectively acquired at four predetermined time points before and after two vaccine doses in a multicentre observational controlled study. The primary outcome was humoral immune response and vaccination safety in IBD patients. We performed trajectory analysis to identify the degree of immune response and associated factors in IBD patients compared with controls.

RESULTS

Overall, 645 IBD patients and 199 control participants were analysed. At 3 months after the second vaccination, the seronegative proportions were 20.3% (combination of anti-tumour necrosis factor [TNF]α and thiopurine) and 70.0% (triple combination including steroids), despite that 80.0% receiving the triple combination therapy were seropositive at 4 weeks after the second vaccination. Trajectory analyses indicated three degrees of change in immune response over time in IBD patients: high (57.7%), medium (35.6%), and persistently low (6.7%). In the control group, there was only one degree, which corresponded with IBD high responders. Older age, combined anti-TNFα and thiopurine (odds ratio [OR], 37.68; 95% confidence interval [CI], 5.64-251.54), steroids (OR, 21.47; 95%CI, 5.47-84.26), and tofacitinib (OR, 10.66; 95%CI, 1.49-76.31) were factors associated with persistently low response. Allergy history (OR, 0.17; 95%CI, 0.04-0.68) was a negatively associated factor. Adverse reactions after the second vaccination were significantly fewer in IBD than controls (31.0% vs 59.8%; p < 0.001).

CONCLUSIONS

Most IBD patients showed a sufficient immune response to COVID-19 vaccination regardless of clinical factors. Assessment of changes over time is essential to optimize COVID-19 vaccination, especially in persistently low responders.

Febrile Reactions Associated with High IgG Antibody Titers after the Second and Third BNT162b2 Vaccinations in Japan

Adverse events are potentially associated with an IgG response after BNT162b2 vaccination for severe acute respiratory syndrome coronavirus 2. In this study, we investigated the side effects of the BNT162b2 vaccine using a health questionnaire and examined its relationship with IgG antibody titers. Serum samples were collected from participants 3 months after the second vaccination, immediately before the third vaccination, and 1 and 3 months after the third vaccination. A total of 505 participants who received three doses of vaccine were eligible for inclusion in the analysis. The results showed that post-vaccination body temperature correlated with anti-spike-receptor-binding domain (anti-S-RBD) antibody titers measured 3 months after the second (r = 0.30, P < 0.001) and third (r = 0.14, P < 0.001) vaccinations. Multivariate linear regression analysis revealed that age and severe swelling were negatively associated, whereas female sex, body temperature, and heat sensation were positively associated with log-transformed anti-S-RBD antibody levels after the second vaccination. After the third vaccination, body temperature and fatigue were positively associated, and female sex was negatively associated, with the log-transformed anti-S-RBD antibody levels. These results suggest that post-vaccination fever may be a marker of a high antibody titer.

Comparison of humoral and cellular immune responses in hematologic diseases following completed vaccination protocol with BBIBP-CorV, or AZD1222, or BNT162b2 vaccines against SARS-CoV-2

Background

Vaccination has proven the potential to control the COVID-19 pandemic worldwide. Although recent evidence suggests a poor humoral response against SARS-CoV-2 in vaccinated hematological disease (HD) patients, data on vaccination in these patients is limited with the comparison of mRNA-based, vector-based or inactivated virus-based vaccines.

Methods

Forty-nine HD patients and 46 healthy controls (HCs) were enrolled who received two-doses complete vaccination with BNT162b2, or AZD1222, or BBIBP-CorV, respectively. The antibodies reactive to the receptor binding domain of spike protein of SARS-CoV-2 were assayed by Siemens ADVIA Centaur assay. The reactive cellular immunity was assayed by flow cytometry. The PBMCs were reactivated with SARS-CoV-2 antigens and the production of activation-induced markers (TNF-α, IFN-γ, CD40L) was measured in CD4+ or CD8+ T-cells ex vivo.

Results

The anti-RBD IgG level was the highest upon BNT162b2 vaccination in HDs (1264 BAU/mL) vs. HCs (1325 BAU/mL) among the studied groups. The BBIBP-CorV vaccination in HDs (339.8 BAU/mL ***p < 0.001) and AZD1222 in HDs (669.9 BAU/mL *p < 0.05) resulted in weaker antibody response vs. BNT162b2 in HCs. The response rate of IgG production of HC vs. HD patients above the diagnostic cut-off value was 100% vs. 72% for the mRNA-based BNT162b2 vaccine; 93% vs. 56% for the vector-based AZD1222, or 69% vs. 33% for the inactivated vaccine BBIBP-CorV, respectively. Cases that underwent the anti-CD20 therapy resulted in significantly weaker (**p < 0.01) anti-RBD IgG level (302 BAU/mL) than without CD20 blocking in the HD group (928 BAU/mL). The response rates of CD4+ TNF-α+, CD4+ IFN-γ+, or CD4+ CD40L+ cases were lower in HDs vs. HCs in all vaccine groups. However, the BBIBP-CorV vaccine resulted the highest CD4+ TNF-α and CD4+ IFN-γ+ T-cell mediated immunity in the HD group.

Conclusion

We have demonstrated a significant weaker overall response to vaccines in the immunologically impaired HD population vs. HCs regardless of vaccine type. Although, the humoral immune activity against SARS-CoV-2 can be highly evoked by mRNA-based BNT162b2 vaccination compared to vector-based AZD1222 vaccine, or inactivated virus vaccine BBIBP-CorV, whereas the CD4+ T-cell mediated cellular activity was highest in HDs vaccinated with BBIBP-CorV.

A cohort study reveals different dynamics of SARS-CoV-2-specific antibody formation after Comirnaty and Vaxzevria vaccination

The Coronavirus (COVID-19) Disease Pandemic, caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), has affected millions of people worldwide, prompting a collective effort from the global scientific community to develop a vaccine against it. This study purports to investigate the influence of factors such as sex, age, type of vaccination (Comirnaty, BNT162b2, Pfizer Inc. or Vaxzevria, ChAdOx1-S, Oxford/AstraZeneca), and time since vaccine administration on the process of antibody production. Both of them are based on the introduction of SARS-CoV-2 spike protein (S protein) to the body using different mechanisms (mRNA and recombinant adenovirus, respectively). S protein is responsible for host cell attachment and penetration via its receptor-binding domain (RBD domain). The level of anti-RBD IgG antibodies was tested with an ELISA-based immunodiagnostic assay in serum samples from a total of 1395 patients at 3 time points: before vaccination, after the first dose, and after the second dose. Our novel statistical model, the Generalized Additive Model, revealed variability in antibody production dynamics for both vaccines. Interestingly, no discernible variation in antibody levels between men and women was found. A nonlinear relationship between age and antibody production was observed, characterized by decreased antibody levels for people up to 30 and over 60 years of age, with a lack of correlation in the middle age range. Collectively, our findings further the understanding of the mechanism driving vaccine-induced immunity. Additionally, we propose the Generalized Additive Model as a standardized way of presenting data in similar research.

A Systematic Review and Meta-Analysis Comparing the Diagnostic Accuracy Tests of COVID-19

In this paper, we present a systematic review and meta-analysis that aims to evaluate the reliability of coronavirus disease diagnostic tests in 2019 (COVID-19). This article seeks to describe the scientific discoveries made because of diagnostic tests conducted in recent years during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Between 2020 and 2021, searches for published papers on the COVID-19 diagnostic were made in the PubMed database. Ninety-nine scientific articles that satisfied the requirements were analyzed and included in the meta-analysis, and the specificity and sensitivity of the diagnostic accuracy were assessed. When compared to serological tests such as the enzyme-linked immunosorbent assay (ELISA), chemiluminescence immunoassay (CLIA), lateral flow immunoassay (LFIA), and chemiluminescent microparticle immunoassay (CMIA), molecular tests such as reverse transcription polymerase chain reaction (RT-PCR), reverse transcription loop-mediated isothermal amplification (RT-LAMP), and clustered regularly interspaced short palindromic repeats (CRISPR) performed better in terms of sensitivity and specificity. Additionally, the area under the curve restricted to the false-positive rates (AUC_FPR) of 0.984 obtained by the antiviral neutralization bioassay (ANB) diagnostic test revealed significant potential for the identification of COVID-19. It has been established that the various diagnostic tests have been effectively adapted for the detection of SARS-CoV-2; nevertheless, their performance still must be enhanced to contain potential COVID-19 outbreaks, which will also help contain potential infectious agent outbreaks in the future.

Heterologous Vector-mRNA Based SARS-CoV-2 Vaccination Strategy Appears Superior to a Homologous Vector-Based Vaccination Scheme in German Healthcare Workers Regarding Humoral SARS-CoV-2 Response Indicating a High Boosting Effect by mRNA Vaccines

BACKGROUND

Longitudinal humoral SARS-CoV-2 (severe acute respiratory syndrome coronavirus type 2) immunity for up to 15 months due to vaccination, the efficacy of vaccination strategies (homologous, vector-vector versus heterologous, vector-mRNA), the influence of vaccination side effects, and the infection rate in German healthcare workers need to be investigated.

METHODS

In this study, 103 individuals vaccinated against SARS-CoV-2 were enrolled to examine their anti-SARS-CoV-2 anti-N- and anti-RBD/S1-Ig levels. A total of 415 blood samples in lithium heparin tubes were prospectively obtained, and a structured survey regarding medical history, type of vaccine, and vaccination reactions was conducted.

RESULTS

All participants demonstrated a humoral immune response, among whom no values decreased below the positivity cutoff. Five to six months after the third vaccination, three participants showed anti-RBD/S1 antibodies of less than 1000 U/mL. We observed higher levels for heterologous mRNA-/vector-based combinations compared to pure vector-based vaccination after the second vaccination, which is harmonized after a third vaccination with the mRNA-vaccine only in both cohorts. The incidence of vaccine breakthrough in a highly exposed cohort was 60.3%.

CONCLUSION

Sustained long-term humoral immunity was observed, indicating the superiority of a heterologous mRNA-/vector-based combination compared to pure vector-based vaccination. There was longevity of anti-RBD/S1 antibodies of at least 4 and up to 7 months without external stimulus. Regarding vaccination reactogenity, the occurrence of local symptoms as pain at the injection site was increased after the first mRNA application compared to the vector-vector cohort with a general decrease in adverse events at later vaccination time points. Overall, a correlation between the humoral vaccination response and vaccination side effects was not observed. Despite the high prevalence of vaccine breakthroughs, these only occurred in the later course of the study when more infectious variants, which are, however, associated with milder courses, were present. These results provide insights into vaccine-related serologic responses, and the study should be expanded using additional vaccine doses and novel variants in the future.

Long-term effects of COVID-19 on lungs and the clinical relevance: a 6-month prospective cohort study

Background: We aimed to explore the prevalence of prolonged symptoms, pulmonary impairments and residual disease on chest tomography (CT) in COVID-19 patients at 6 months after acute illness. Methods: In this prospective, single-center study, hospitalized patients with radiologically and laboratory-confirmed COVID-19 were included. Results: A high proportion of the 116 patients reported persistent symptoms (n = 54; 46.6%). On follow-up CT, 33 patients (28.4%) demonstrated residual disease. Multivariate analyses revealed that only neutrophil-to-lymphocyte ratio was an independent predictor for residual disease. Conclusion: Hospitalized patients with mild/moderate COVID-19 still had persistent symptoms and were prone to develop long-term pulmonary sequelae on chest CT. However, it did not have a significant effect on long-term pulmonary functions.

Pulmonary recovery from COVID-19 in patients with metabolic diseases: a longitudinal prospective cohort study

The severity of coronavirus disease 2019 (COVID-19) is related to the presence of comorbidities including metabolic diseases. We herein present data from the longitudinal prospective CovILD trial, and investigate the recovery from COVID-19 in individuals with dysglycemia and dyslipidemia. A total of 145 COVID-19 patients were prospectively followed and a comprehensive clinical, laboratory and imaging assessment was performed at 60, 100, 180, and 360 days after the onset of COVID-19. The severity of acute COVID-19 and outcome at early post-acute follow-up were significantly related to the presence of dysglycemia and dyslipidemia. Still, at long-term follow-up, metabolic disorders were not associated with an adverse pulmonary outcome, as reflected by a good recovery of structural lung abnormalities in both, patients with and without metabolic diseases. To conclude, dyslipidemia and dysglycemia are associated with a more severe course of acute COVID-19 as well as delayed early recovery but do not impair long-term pulmonary recovery.

Humoral and Cellular Immune Responses against SARS-CoV-2 after Third Dose BNT162b2 following Double-Dose Vaccination with BNT162b2 versus ChAdOx1 in Patients with Cancer

PURPOSE

Patients with cancer display reduced humoral responses after double-dose COVID-19 vaccination, whereas their cellular response is more comparable with that in healthy individuals. Recent studies demonstrated that a third vaccination dose boosts these immune responses, both in healthy people and patients with cancer. Because of the availability of many different COVID-19 vaccines, many people have been boosted with a different vaccine from the one used for double-dose vaccination. Data on such alternative vaccination schedules are scarce. This prospective study compares a third dose of BNT162b2 after double-dose BNT162b2 (homologous) versus ChAdOx1 (heterologous) vaccination in patients with cancer.

EXPERIMENTAL DESIGN

A total of 442 subjects (315 patients and 127 healthy) received a third dose of BNT162b2 (230 homologous vs. 212 heterologous). Vaccine-induced adverse events (AE) were captured up to 7 days after vaccination. Humoral immunity was assessed by SARS-CoV-2 anti-S1 IgG antibody levels and SARS-CoV-2 50% neutralization titers (NT50) against Wuhan and BA.1 Omicron strains. Cellular immunity was examined by analyzing CD4+ and CD8+ T-cell responses against SARS-CoV-2-specific S1 and S2 peptides.

RESULTS

Local AEs were more common after heterologous boosting. SARS-CoV-2 anti-S1 IgG antibody levels did not differ significantly between homologous and heterologous boosted subjects [GMT 1,755.90 BAU/mL (95% CI, 1,276.95-2,414.48) vs. 1,495.82 BAU/mL (95% CI, 1,131.48-1,977.46)]. However, homologous-boosted subjects show significantly higher NT50 values against BA.1 Omicron. Subjects receiving heterologous boosting demonstrated increased spike-specific CD8+ T cells, including higher IFNγ and TNFα levels.

CONCLUSIONS

In patients with cancer who received double-dose ChAdOx1, a third heterologous dose of BNT162b2 was able to close the gap in antibody response.

Quantifying the Vaccine-Induced Humoral Immune Response to Spike-Receptor Binding Domain as a Surrogate for Neutralization Testing Following mRNA-1273 (Spikevax) Vaccination Against COVID-19

INTRODUCTION

There is a need for automated, high-throughput assays to quantify immune response after SARS-CoV-2 vaccination. This study assessed the combined utility of the Elecsys^® Anti-SARS-CoV-2 S (ACOV2S) and the Elecsys Anti-SARS-CoV-2 (ACOV2N) assays using samples from the mRNA-1273 (Spikevax™) phase 2 trial (NCT04405076).

METHODS

Samples from 593 healthy participants in two age cohorts (18-54 and ≥ 55 years), who received two injections with placebo (n = 198) or mRNA-1273 (50 μg [n = 197] or 100 μg [n = 198]), were collected at days 1 (first vaccination), 15, 29 (second vaccination), 43, and 57. ACOV2S results were used to assess humoral response to vaccination in different subgroups and were compared to live virus microneutralization assay. Samples from patients with either previous or concomitant infection (identified per ACOV2N) were analyzed separately.

RESULTS

Receptor-binding domain-specific antibodies were readily detectable by ACOV2S for the vast majority of participants (174/189, 92.1% [50 μg dose] and 178/192, 92.7% [100 μg dose]) at the first post-vaccination assessment, with non-converters predominantly older in age. Seroconversion for all participants was observed at day 29 (before the second vaccine dose). Two weeks after the first dose, geometric mean concentration (GMC) of antibody levels was 1.37-fold higher in the 100 versus 50 μg group (p = 0.0098), reducing to 1.09-fold 2 weeks after the second dose (p = 0.0539, n.s.). In both dose groups, a more pronounced response was observed in the younger versus older age group on day 15 (50 μg, 2.49-fold [p < 0.0001]; 100 μg, 3.94-fold [p < 0.0001] higher GMC, respectively), and day 29 (1.93-fold, p = 0.0002, and 2.44-fold, p < 0.0001). Eight subjects had previous or concomitant SARS-CoV-2 infection; vaccination boosted their humoral response to very high ACOV2S results compared to infection-naïve recipients. ACOV2S strongly correlated with microneutralization (Pearson's r = 0.779; p < 0.0001), including good qualitative agreement.

CONCLUSION

These results confirmed that ACOV2S is a highly valuable assay for tracking vaccine-related immune responses. Combined application with ACOV2N enables monitoring for breakthrough infection or stratification of previous natively infected individuals. The adaptive measuring range and high resolution of ACOV2S allow for early identification of seroconversion and resolution of very high titers and longitudinal differences between subgroups. Additionally, good correlation with live virus microneutralization suggests that ACOV2S is a reliable estimate of neutralization capacity in routine diagnostic settings.

Anti-spike protein to determine SARS-CoV-2 antibody levels: Is there a specific threshold conferring protection in immunocompromised patients?

BACKGROUND

Identifying a specific threshold level of SARS-CoV-2 antibodies that confers protection in immunocompromised patients has been very challenging. The aim was to assess the threshold of 264 binding antibody units (BAU)/ml using four different SARS-CoV-2 antibody assays (Abbott, Beckman, Roche, and Siemens) and to establish a new optimal threshold of protection for each of the four antibody assays.

METHODS

This study was performed on data retrieved from 69 individuals, who received at least one dose of the Pfizer/BioNTech BNT162b2 or Moderna COVID-19 vaccine (Spikevax) at the Alphabio Laboratory in Marseille, France (European Hospital, Alphabio-Biogroup). The results were compared to the percent inhibition calculated using a functional surrogate of a standardized virus neutralization test (Genscript).

RESULTS

Samples from 69 patients were analyzed. For a reference cutoff of 264 BAU/ml, assays showed moderate to good overall concordance with Genscript: 87% concordance for Abbott, 78% for Beckman, 75% for Roche, and 88% for Siemens. Overall concordance increased consistently after applying new thresholds, i.e., 148 BAU/ml (Abbott), 48 (Beckman), 559 (Roche), and 270 (Siemens).

CONCLUSION

We suggest specific adjusted thresholds (BAU/ml) for the four commercial antibody assays that are used to assess pre-exposure prophylaxis in immunocompromised patients.

SARS-CoV-2 Anti-Spike IgG Antibody and ACE2 Receptor Binding Inhibition Levels among Breakthrough Stage Veteran Patients

SARS-CoV-2 mRNA vaccines have been critical to curbing pandemic COVID-19; however, a major shortcoming has been the inability to assess levels of protection after vaccination. This study assessed serologic status of breakthrough infections in vaccinated patients at a Veterans Administration medical center from June through December 2021 during a SARS-CoV-2 delta variant wave. Breakthrough occurred mostly beyond 150 days after two-dose vaccination with a mean of 239 days. Anti-SARS-CoV-2 spike (S) IgG levels were low at 0 to 2 days postsymptoms but increased in subjects presenting thereafter. Population measurements of anti-S IgG and angiotensin converting enzyme-2 receptor (ACE2-R) binding inhibition among uninfected, vaccinated patients suggested immune decay occurred after 150 days with 62% having anti-S IgG levels at or below 1,000 AU comparable with breakthrough patients at 0 to 2 days postsymptom onset. In contrast, vaccination after resolved infection conferred robust enduring anti-S IgG levels (5,000 to >50,000 AU) with >90% ACE2-R binding inhibition. However, monoclonal antibody (MAb)-treated patients did not benefit from their prior infection suggesting impaired establishment of B cell memory. Analysis of boosted patients confirmed the benefit of a third vaccine dose with most having anti-S IgG levels above 5,000 AU with >90% ACE2-R binding inhibition, but a subset had levels <5,000 AU. Anti-S IgG levels >5,000 AU were associated with >90% ACE2-R binding inhibition and no documented breakthrough infections, whereas levels falling below 5,000 AU and approaching 1,000 AU were associated with breakthrough infections. Thus, quantitative antibody measurements may provide a means to guide vaccination intervals for the individual. IMPORTANCE Currently, clinicians have no guidance for the serologic assessment of SARS-Cov-2 postvaccination status regarding protection and risk of infection. Vaccination and boosters are administered blindly without evaluation of need or outcome at the individual level. The recent development of automated quantitative assays for anti-SARS-CoV-2 spike protein IgG antibodies permits accurate measurement of humoral immunity in standardized units. Clinical studies, such as reported here, will help establish protective antibody levels allowing identification and targeted management of poor vaccine responders and vaccinated subjects undergoing immune decay.

One-Year Follow-Up of COVID-19 Patients Indicates Substantial Assay-Dependent Differences in the Kinetics of SARS-CoV-2 Antibodies

Determination of antibody levels against the nucleocapsid (N) and spike (S) proteins of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are used to estimate the humoral immune response after SARS-CoV-2 infection or vaccination. Differences in the design and specification of antibody assays challenge the interpretation of test results, and comparative studies are often limited to single time points per patient. We determined the longitudinal kinetics of antibody levels of 145 unvaccinated coronavirus disease 2019 (COVID-19) patients at four visits over 1 year upon convalescence using 8 commercial SARS-CoV-2 antibody assays (from Abbott, DiaSorin, Roche, Siemens, and Technoclone), as well as a virus neutralization test (VNT). A linear regression model was used to investigate whether antibody results obtained in the first 6 months after disease onset could predict the VNT results at 12 months. Spike protein-specific antibody tests showed good correlation to the VNT at individual time points (rS, 0.74 to 0.92). While longitudinal assay comparison with the Roche Elecsys anti-SARS-CoV-2 S test showed almost constant antibody concentrations over 12 months, the VNT and all other tests indicated a decline in serum antibody levels (median decrease to 14% to 36% of baseline). The antibody level at 3 months was the best predictor of the VNT results at 12 months after disease onset. The current standardization to a WHO calibrator for normalization to binding antibody units (BAU) is not sufficient for the harmonization of SARS-CoV-2 antibody tests. Assay-specific differences in absolute values and trends over time need to be considered when interpreting the course of antibody levels in patients. IMPORTANCE Determination of antibodies against SARS-CoV-2 will play an important role in detecting a sufficient immune response. Although all the manufacturers expressed antibody levels in binding antibody units per milliliter, thus suggesting comparable results, we found discrepant behavior between the eight investigated assays when we followed the antibody levels in a cohort of 145 convalescent patients over 1 year. While one assay yielded constant antibody levels, the others showed decreasing antibody levels to a varying extent. Therefore, the comparability of the assays must be improved regarding the long-term kinetics of antibody levels. This is a prerequisite for establishing reliable antibody level cutoffs for sufficient individual protection against SARS-CoV-2.

Inactivated Vaccine-Induced SARS-CoV-2 Variant-Specific Immunity in Children

Multiple vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been evaluated in clinical trials. However, trials addressing the immune response in the pediatric population are scarce. The inactivated vaccine CoronaVac has been shown to be safe and immunogenic in a phase 1/2 clinical trial in a pediatric cohort in China. Here, we report interim safety and immunogenicity results of a phase 3 clinical trial for CoronaVac in healthy children and adolescents in Chile. Participants 3 to 17 years old received two doses of CoronaVac in a 4-week interval until 31 December 2021. Local and systemic adverse reactions were registered for volunteers who received one or two doses of CoronaVac. Whole-blood samples were collected from a subgroup of 148 participants for humoral and cellular immunity analyses. The main adverse reaction reported after the first and second doses was pain at the injection site. Four weeks after the second dose, an increase in neutralizing antibody titer was observed in subjects relative to their baseline visit. Similar results were found for activation of specific CD4⁺ T cells. Neutralizing antibodies were identified against the Delta and Omicron variants. However, these titers were lower than those for the D614G strain. Importantly, comparable CD4⁺ T cell responses were detected against these variants of concern. Therefore, CoronaVac is safe and immunogenic in subjects 3 to 17 years old, inducing neutralizing antibody secretion and activating CD4⁺ T cells against SARS-CoV-2 and its variants. (This study has been registered at ClinicalTrials.gov under no. NCT04992260.) IMPORTANCE This work evaluated the immune response induced by two doses of CoronaVac separated by 4 weeks in healthy children and adolescents in Chile. To date, few studies have described the effects of CoronaVac in the pediatric population. Therefore, it is essential to generate knowledge regarding the protection of vaccines in this population. Along these lines, we reported the anti-S humoral response and cellular immune response to several SARS-CoV-2 proteins that have been published and recently studied. Here, we show that a vaccination schedule consisting of two doses separated by 4 weeks induces the secretion of neutralizing antibodies against SARS-CoV-2. Furthermore, CoronaVac induces the activation of CD4⁺ T cells upon stimulation with peptides from the proteome of SARS-CoV-2. These results indicate that, even though the neutralizing antibody response induced by vaccination decreases against the Delta and Omicron variants, the cellular response against these variants is comparable to the response against the ancestral strain D614G, even being significantly higher against Omicron.

Low Peripheral B-Cell Counts in Patients With Systemic Rheumatic Diseases Due to Treatment With Belimumab and/or Rituximab Are Associated With Low Antibody Responses to Primary COVID-19 Vaccination

Background: Immunosuppressive agents inhibit COVID-19 vaccine antibody (Ab) responses in patients with systemic rheumatic diseases. Rituximab may fully block Ab responses when B cells become undetected. The effect of detected but low number of B cells due to treatment with a B-cell agent (belimumab and/or rituximab) has not been established. Purpose: We sought to examine whether there is an association between a low number of B cells due to treatment with belimumab and/or rituximab and impaired primary COVID-19 vaccination spike Ab responses in patients with systemic rheumatic diseases. Methods: We retrospectively examined Ab responses to COVID-19 vaccinations, especially in relation to B-cell counts after treatment with belimumab and/or rituximab, in 58 patients with systemic rheumatic diseases: 22 on and 36 not on B-cell agents. We used Kruskal-Wallis and Mann-Whitney U tests for comparison of Ab values between the groups and Fisher exact test for relative risk calculations. Results: Median (interquartile range) postvaccination Ab responses were lower in patients on versus those not on B-cell agents: 3.91 (0.77–20.00) versus 20.00 (14.32–20.00), respectively. Among patients on belimumab and/or rituximab, Ab responses of less than 25% of the assay’s upper limit were exclusively observed in those with B-cell counts lower than 40/µL. Patients with B-cell counts lower than 40/µL exhibit a relative risk of 6.092 (95% CI: 2.75–14.24) for Ab responses of less than 25% of the upper limit compared with patients not on B-cell agents. This relative risk remained significant, even after excluding patients with undetected B cells. Conclusion: This retrospective study found an association between low B-cell counts (less than 40/µL) and decreased Ab responses to primary COVID-19 vaccination in patients with systemic rheumatic diseases treated with belimumab and/or rituximab. Despite the small number of patients studied, these findings add to the accumulating evidence on the importance of B-cell count in predicting spike Ab responses to COVID-19 vaccination.

Long-term observation of antibody titers against SARS-CoV-2 following vaccination

Objectives

We aimed to understand how SARS-CoV-2 antibody titer decrease following SARS-CoV-2 mRNA vaccination and to estimate the timing of booster vaccination.

Study design

Six hundred sixty-two healthcare workers were administered with total of three doses of SARS-CoV-2 mRNA vaccine during the same short period. Of them, three volunteers were enrolled to measure anti-receptor binding domain (RBD) antibody titers (IgG) monthly following the second and the third doses.

Methods

Serum anti-RBD antibody titers were measured monthly and the decay curve of the antibody was analyzed. We estimate the timing of the third and fourth vaccine based on the observed antibody titer decrease and the period of breakthrough infections in the vaccine recipients.

Results

Anti-RBD antibody decreased exponentially following the 2nd dose. Between 108 and 117 days following the second dose, breakthrough infection of SARS-CoV-2 occurred in 11 out of the 662 vaccine recipients. Based on the decrease in anti-RBD antibody and the timing of the breakthrough infections, we estimate that the optimal timing of a third dose would be at earliest 108 days after the second dose, when anti-RBD antibody titers are less than 338 BAU/mL. The anti-RBD antibody titers were sustained relatively higher for 161 days following the third dose (416 days following the second dose).

Conclusions

We estimate that the optimal timing of a third dose would be at earliest 108 days after the second dose, or anti-RBD antibody titers are less than 338 BAU/mL. We suggest that a fourth dose should be administered later than 161 days following the third dose.

Evaluation of the analytical performance of three chemiluminescence serological assays for detecting anti-SARS-CoV-2 antibodies

The serology surveillance of SARS-CoV-2 antibodies represents a useful tool for monitoring protective immunity in the population. We compared the performance of three SARS-CoV-2 antibody serological immunoassays in 600 vaccinated subjects after the BNT162b2 mRNA COVID-19 vaccine. All serum samples were evaluated by three different immunoassays for detecting anti-SARS-COV-2 antibodies. All SARS-CoV-2 antibody serological immunoassays could detect, when present, a post-vaccine humoral immune response. Median (interquartile range, IQR) anti-S-RBD IgG, Access SARS-CoV-2 IgG (1st IS) and Access SARS-CoV-2 IgG II levels of the subjects investigated were, respectively, 687 BAU/mL (131–2325), 419 IU/mL (58–1091) and 104 AU/mL (14–274). By studying a cohort of unvaccinated subjects, without previous COVID-19 infection, we found a high specificity for all methods. A high correlation was found between IgG titres. Considering the kinetics of subjects with multiple doses, we observed that percentage decreasing gradients were comparable across methods. Our results suggest that all the SARS-CoV-2 antibody serological immunoassays evaluated in this study are suitable for monitoring IgG titers over time. This study contributes to a better understanding of antibody response in vaccinated subjects using some currently available assays.

A novel assessment method for COVID-19 humoral immunity duration using serial measurements in naturally infected and vaccinated subjects

BACKGROUND

Collecting information on sustainability of immune responses after infection or vaccination is crucial to inform medical decision-making and vaccination strategies. Data on how long-lasting antibodies against SARS-COV-2 could provide a humoral and protective immunity and prevent reinfection with SARS-CoV-2 or its variants is particularly valuable. This study presents a novel method to quantitatively measure and monitor the diversity of SARS-CoV-2 specific antibody profiles over time.

METHODS

Serum samples from two groups were used in this study: Samples from 20 naturally infected subjects (followed for up to 1 year) and samples from 83 subjects vaccinated with one or two doses of the Pfizer BioNtech vaccine (BNT162b2/BNT162b2) (followed for up to 6 months). The Multi-SARS-CoV-2 assay, a multiparameter serology test developed for the serological confirmation of past-infections, was used to determine the reactivity of six different SARS-CoV-2 antigens. For each subject sample, 3 dilutions (1/50, 1/400 and 1/3200) were defined as an optimal set over the six antigens and their respective linear ranges. This allowed accurate quantification of the corresponding six antibodies. Nonlinear mixed-effects modelling was applied to convert intensity readings from 3 determined dilutions to a single quantification value for each antibody.

RESULTS

Median half-life for the 20 naturally infected vs 74 vaccinated subjects (two doses) was 120 vs 50 days for RBD, 127 vs 53 days for S1 and 187 vs 86 days for S2 antibodies respectively.

CONCLUSION

The newly proposed method, based on a series of a limited number of dilutions, can convert a conventional qualitative assay into a quantitative assay. This conversion helps define the sustainability of specific immune responses against each relevant viral antigen and can help in defining the protection characteristics after an infection or a vaccination.

Comparison of Homologous and Heterologous Booster SARS-CoV-2 Vaccination in Autoimmune Rheumatic and Musculoskeletal Patients

Vaccination against SARS-CoV-2 to prevent COVID-19 is highly recommended for immunocompromised patients with autoimmune rheumatic and musculoskeletal diseases (aiRMDs). Little is known about the effect of booster vaccination or infection followed by previously completed two-dose vaccination in aiRMDs. We determined neutralizing anti-SARS-CoV-2 antibody levels and applied flow cytometric immunophenotyping to quantify the SARS-CoV-2 reactive B- and T-cell mediated immunity in aiRMDs receiving homologous or heterologous boosters or acquired infection following vaccination. Patients receiving a heterologous booster had a higher proportion of IgM+ SARS-CoV-2 S+ CD19+CD27+ peripheral memory B-cells in comparison to those who acquired infection. Biologic therapy decreased the number of S+CD19+; S+CD19+CD27+IgG+; and S+CD19+CD27+IgM+ B-cells. The response rate to a booster event in cellular immunity was the highest in the S-, M-, and N-reactive CD4+CD40L+ T-cell subset. Patients with a disease duration of more than 10 years had higher proportions of CD8+TNF-α+ and CD8+IFN-γ+ T-cells in comparison to patients who were diagnosed less than 10 years ago. We detected neutralizing antibodies, S+ reactive peripheral memory B-cells, and five S-, M-, and N-reactive T-cells subsets in our patient cohort showing the importance of booster events. Biologic therapy and <10 years disease duration may confound anti-SARS-CoV-2 specific immunity in aiRMDs.

The Waxing, Waning, and Predictors of Humoral Responses to Vector-Based SARS-CoV-2 Vaccine in Hemodialysis Patients

Hemodialysis (HD) patients are vulnerable to coronavirus disease 2019 (COVID-19) and have a high mortality rate. We evaluated the anti-SARS-CoV-2 spike protein antibody (ACOV2S) levels in 385 HD patients before and 4 and 8 weeks after the second dose of vector-based ChAdOx1 nCoV-19 vaccine. For study control, week 4 ACOV2S levels after the second vaccination dose were measured in 66 healthcare workers (HCWs). The seroconversion rate of HD patients was 98.96% 4 weeks after the second vaccination. Despite low antibody levels before the second dose (week 0), week 4 ACOV2S levels after the second vaccine dose in HD patients increased prominently and were compatible with those in HCWs (p = 0.814 for HCWs vs. HD patients). The ACOV2S levels in HD patients waned significantly 8 weeks after the second vaccination dose (p < 0.001 at week 8 vs. 4). Older age and immunosuppressant use were negative predictors, while higher C-reactive protein (CRP) levels were positive predictors of ACOV2S waxing after the second vaccine dose in HD patients. Higher CRP levels and platelet counts were independently associated with decreased ACOV2S waning. The ChAdOx1 nCoV-19 vaccine is effective and safe for primary vaccination in HD patients and a booster dose is necessary.

Antibody and T-cell responses by ultra-deep T-cell receptor immunosequencing after COVID-19 vaccination in patients with plasma cell dyscrasias

We investigated antibody and coronavirus disease 2019 (COVID‐19)‐specific T‐cell mediated responses via ultra‐deep immunosequencing of the T‐cell receptor (TCR) repertoire in patients with plasma cell dyscrasias (PCD). We identified 364 patients with PCD who underwent spike antibody testing using commercially available spike‐receptor binding domain immunoglobulin G antibodies ≥2 weeks after completion of the initial two doses of mRNA vaccines or one dose of JNJ‐78436735. A total of 56 patients underwent TCR immunosequencing after vaccination. Overall, 86% tested within 6 months of vaccination had detectable spike antibodies. Increasing age, use of anti‐CD38 or anti‐B‐cell maturation antigen therapy, and receipt of BNT162b2 (vs. mRNA‐1273) were associated with lower antibody titres. We observed an increased proportion of TCRs associated with surface glycoprotein regions of the COVID‐19 genome after vaccination, consistent with spike‐specific T‐cell responses. The median spike‐specific T‐cell breadth was 3.11 × 10⁻⁵, comparable to those in healthy populations after vaccination. Although spike‐specific T‐cell breadth correlated with antibody titres, patients without antibody responses also demonstrated spike‐specific T‐cell responses. Patients receiving mRNA‐1273 had higher median spike‐specific T‐cell breadth than those receiving BNT162b2 (p = 0.01). Although patients with PCD are often immunocompromised due to underlying disease and treatments, COVID‐19 vaccination can still elicit humoral and T‐cell responses and remain an important intervention in this patient population.

COVID-19 and plasma cells: Is there long-lived protection?

Infection with SARS-CoV-2, the etiology of the ongoing COVID-19 pandemic, has resulted in over 450 million cases with more than 6 million deaths worldwide, causing global disruptions since early 2020. Memory B cells and durable antibody protection from long-lived plasma cells (LLPC) are the mainstay of most effective vaccines. However, ending the pandemic has been hampered by the lack of long-lived immunity after infection or vaccination. Although immunizations offer protection from severe disease and hospitalization, breakthrough infections still occur, most likely due to new mutant viruses and the overall decline of neutralizing antibodies after 6 months. Here, we review the current knowledge of B cells, from extrafollicular to memory populations, with a focus on distinct plasma cell subsets, such as early-minted blood antibody-secreting cells and the bone marrow LLPC, and how these humoral compartments contribute to protection after SARS-CoV-2 infection and immunization.

Response to three doses of the Pfizer/BioNTech BNT162b2 COVID-19 vaccine: a retrospective study of a cohort of haemodialysis patients in France

BACKGROUND

The mortality rate associated with coronavirus disease 2019 (COVID-19) is high among haemodialyzed patients. We sought to describe the serological status of haemodialysis patients having received up to three doses of BNT162b2 mRNA vaccine, and to identify factors associated with a poor humoral response.

METHODS

We performed a retrospective, observational study of patients attending a dialysis centre in Antibes, France. One or two of each patient's monthly venous blood samples were assayed for anti-spike (S1) immunoglobulin G (IgG).

RESULTS

We included 142 patients, of whom 124 remained COVID-19-negative throughout the study. Among these COVID-19-negative patients, the humoral immune response rate (defined as an anti-S1 IgG titre ≥1.2 U/ml) was 82.9% after two injections and 95.8% after three injections, and the median [interquartile range] titre increased significantly from 7.09 [2.21; 19.94] U/ml with two injections to 93.26 [34.25; 176.06] U/ml with three. Among patients with two injections, the mean body mass index and serum albumin levels were significantly higher in responders than in non-responders (26.5 kg/m2 vs. 23.2 kg/m2, p = 0.0392; and 41.9 g/l vs. 39.0 g/l, p = 0.0042, respectively). For the study population as a whole at the end of the study, a history of COVID-19, at least two vaccine doses, and being on the French national waiting list for kidney transplantation were the only factors independently associated with the anti-S1 IgG titre.

CONCLUSIONS

Dialysis patients vaccinated with two doses of BNT162b2 might not be sufficiently protected against SARS-CoV-2 and so should receive a third (booster) dose.

TRIAL REGISTRATION

The present retrospective study of clinical practice was not interventional and so was not registered.

Immune Response 5–7 Months after Vaccination against SARS-CoV-2 in Elderly Nursing Home Residents in the Czech Republic: Comparison of Three Vaccines

Background and Aims: Elderly nursing home residents are especially prone to a severe course of SARS-CoV-2 infection. In this study, we aimed to investigate the complex immune response after vaccination depending on the convalescence status and vaccine. Methods: Sampling took place in September–October 2021. IgG antibodies against spike protein and nucleocapsid protein, the titer of virus neutralization antibodies against delta and (on a subset of patients) omicron, and cellular immunity (interferon-gamma release assay) were tested in nursing home residents vaccinated with Pfizer, Moderna (both 30–31 weeks after the completion of vaccination), or AstraZeneca (23 weeks) vaccines. The prevalence with 95% confidence intervals (CI) was evaluated in Stata version 17. Results: 95.2% (95% CI: 92.5–97.1%) of the 375 participants had positive results of anti-S IgG, 92.8% (95% CI: 89.7–95.2%) were positive in virus neutralization assay against delta, and 89.0% (95% CI: 84.5–92.5%) in the interferon-gamma-releasing assay detecting cellular immunity. Results of the virus neutralization assay against omicron correlated with those against delta but the neutralization capacity was reduced by about half. As expected, the worst results were found for the AstraZeneca vaccine, although the vaccination-to-test period was the shortest for this vaccine. All immune parameters were significantly higher in convalescent residents than in naive residents after vaccination. No case of COVID-19 occurred during the vaccination-to-test period. Conclusions: A high immune response, especially among vaccinated convalescents (i.e., residents with hybrid immunity), was found in elderly nursing home residents 5–7 months after vaccination against SARS-CoV-2. In view of this, it appears that such residents are much better protected from COVID-19 than those who are only vaccinated and the matter of individual approach to the booster dose in such individuals should be further discussed.

Antibody response to the COVID-19 ChAdOx1nCov-19 and BNT162b vaccines after temporary suspension of DMARD therapy in immune-mediated inflammatory disease (RESCUE)

OBJECTIVE

To assess the antibody response to disease-modifying antirheumatic drug (DMARD) therapy after the first and second dose of the ChAdOx1nCov-19 (AstraZeneca (AZ)) and BNT162b (Pfizer) vaccines in patients with immune-mediated inflammatory disease (IMID) compared with controls and if withholding therapy following the first vaccination dose has any effect on seroconversion and SARS-CoV-2 antibody (Ab) levels.

METHODS

A multicentre three-arm randomised controlled trial compared the immunogenicity of the Pfizer and AZ vaccines in adult patients on conventional synthetic (csDMARD), biologic (bDMARD) or targeted synthetic (tsDMARD) therapy for IMID (n=181) with a control group (n=59). Patients were randomised to continue or withhold DMARD therapy for 1-2 weeks post first dose vaccination only. Serum SARS-CoV-2 IgG detection (IgG ≥1.0 U/mL) and titres against the S1/S2 proteins were measured at baseline, 3-4 weeks post first vaccination and 4 weeks post second vaccination.

RESULTS

AZ vaccination was given to 47.5%, 41.5% and 52.5% in the continue, withhold and control groups, respectively while Pfizer vaccination was given to 52.5%, 58.5% and 47.5% among the continue, withhold and control groups, respectively. Seroconversion rates following the first dose in the AZ and Pfizer groups were only 27.3% vs 79.2% (p=0.000) and 64.58% vs 100% (p=0.000), respectively in the IMID groups who continued therapy compared with the AZ and Pfizer controls, respectively. Withholding DMARD therapy following the first vaccination dose resulted in higher seroconversion to 67.7% and 84.1% in the AZ and Pfizer groups, respectively. Following the second AZ and Pfizer vaccinations when all DMARDs were continued, despite a slightly lower seroconversion rate (83.7% vs 100%, p=0.000 and 95.9% vs 100%, p=0.413), respectively, the mean SARS-CoV2 IgG Ab titres were not significantly different in the csDMARD and bDMARD groups compared with the controls regardless of hold while it was significantly lower in patients taking tsDMARD (12.88 vs 79.49 U/mL, p=0.000).

CONCLUSIONS

Following the first vaccination dose, antibody responses were lower in IMID on DMARD therapy, however the final responses were excellent regardless of hold with the exception of the tsDMARD group where withholding therapy is recommended. At least 2 vaccinations are therefore recommended preferably with an messenger RNA vaccine.

TRIAL REGISTRATION NUMBER

ANZCTR: 12621000661875.

The Fluctuation Trend of Serum Anti-SARS-CoV-2 IgM/IgG Antibodies Seroprevalence in the Non-COVID-19 Infected Population and Correlation with Peripheral Blood Leukocyte Parameters in Beijing, China, 2021: A Real-World Study

Since 2019, the coronavirus disease 2019 (COVID-19) global pandemic has caused more than 300 million cases of disease and 5 million deaths. Vaccination has been widely accepted as the most effective measure for the prevention and control of this disease. However, there is little understanding about serum anti-SARS-CoV-2 IgM/IgG levels after inactivated vaccination as well as the relationship with peripheral blood leukocytes in the non-COVID-19 infected population. A total of 16,335 male and 22,302 female participants were recruited in this study, which was conducted in the Peking University Third Hospital located in Beijing (China). The level and seroprevalence of serum anti-SARS-CoV-2 receptor-binding domain (RBD) IgM/IgG and the association with peripheral blood leukocytes classification were investigated. With an increase in the number and percentage of full immunization of COVID-19 vaccinations in Beijing, serum anti-SARS-CoV-2 IgG antibodies levels and seroprevalence were significantly elevated (p < 0.01). The serum anti-SARS-CoV-2 IgG antibodies of 60 years and older persons were significantly lower than that of individuals that are 18~60 years old (p < 0.01), and there was a positive relationship between serum anti-SARS-CoV-2 IgG antibodies levels and peripheral blood lymphocyte count. The investigation of serum anti-SARS-CoV-2 IgM/IgG antibodies and the peripheral hematological index may prompt and help understand the adaptive immune response of vaccination.

Humoral and Cellular Immunogenicity and Safety of Five Different SARS-CoV-2 Vaccines in Patients With Autoimmune Rheumatic and Musculoskeletal Diseases in Remission or With Low Disease Activity and in Healthy Controls: A Single Center Study

Background

Vaccine-induced immunity is essential for controlling the COVID-19 pandemic. Data on humoral and cellular immunogenicity and safety of different SARS-CoV-2 vaccines in patients with autoimmune rheumatic and musculoskeletal diseases (RMDs) are limited.

Methods

A single center observational study evaluated the immunogenicity and safety of the two-dose regimen of the BBIBP-CorV inactivated, Gam-COVID-Vac and AZD1222 adenovirus-based, and BNT162b2 and mRNA-1273 mRNA-based vaccines in patients with RMDs (n = 89) compared with healthy controls (n = 74). Neutralizing anti-RBD (receptor binding domain) specific antibodies and SARS-CoV-2 specific T-cell response were measured one and four months after the second vaccine dose in parallel with vaccination efficacy and safety.

Results

Disease-specific comparison showed that antibody response at four months was higher in spondylarthropathies compared to rheumatoid arthritis and autoimmune RMDs. Risk factors for reduced immunogenicity included longer disease duration, positive immunoserological profile and anti-CD20 therapy of patients. The rate of positive anti-RBD antibody response for healthy controls versus patients after 4 months post vaccination was 69% vs. 55% for the inactivated viral vaccine BBIBP-CorV, 97% vs. 53% for the pooled data of adenovirus vector-based vaccines Gam-COVID-Vac and AZD1222, or 100% vs. 81% for the pooled data of mRNA vaccines BNT162b2 and mRNA-1273, respectively. Patients who received the Gam-COVID-Vac or mRNA-1273 vaccines had a higher proportion of TNF-α producing CD4+ T-cells upon SARS-CoV-2 antigen stimulation compared to the inactivated viral vaccine.

Conclusion

All five investigated vaccines were immunogenic in the majority of patients and healthy controls with variable antibody and T-cell response and an acceptable safety profile.

Longevity of Humoral Response Six Months Following BNT162b2 Vaccine in Dialysis Patients

Background

End-stage kidney disease substantially increases the risk of severe COVID-19. However, despite early robust immunogenicity of the mRNA-SARS-CoV-2 vaccination in patients with hemodialysis, the longevity of humoral response in this high-risk population is still unknown.

Methods

A prospective cohort study aimed to evaluate the longevity of serologic response in patients with hemodialysis, compared with a control group, 6 months following the second dose of the BNT162b2 vaccine. We assessed antibody response by quantitative measurement of IgG antibodies against the receptor-binding domain of the Spike protein (anti-S1-RBD IgG). Study outcomes were defined as a seropositivity rate and log-transformed anti-S1-RBD IgG levels at 6 months, and the change in antibody levels between 3 and 6 months.

Findings

The cohort included 104 patients with hemodialysis and 84 controls. At a median time of 184 days (IQR, 183–188) following the second dose of the vaccine, 83/104 (79.8%) patients with hemodialysis maintained seropositivity for the anti-S1-RBD IgG level compared to 83/84 (98.8%) in the control group (p < 0.001). The log-transformed antibody level was significantly lower in the hemodialysis group (2.23 ± 0.39 log AU/ml vs. 2.69 ± 0.65 log AU/ml, respectively, p < 0.001). Older age and hypoalbuminemia were the only variables that were found to be associated with reduced log-transformed antibody levels in univariate and multivariate analysis. There was no interaction between dialysis status and an antibody-level decline rate (p = 0.972).

Conclusion

Among patients with hemodialysis, a seropositivity rate and anti-S1-RBD antibody titers were substantially reduced compared with a control group, at 6 months following the second dose of the BNT162b2 vaccine. These findings support the prioritization of patients with hemodialysis for a third “booster” dose.

Quantity of IgG response to SARS-CoV-2 spike glycoprotein predicts pulmonary recovery from COVID-19

The CovILD study is a prospective, multicenter, observational cohort study to systematically follow up patients after coronavirus disease-2019 (COVID-19). We extensively evaluated 145 COVID-19 patients at 3 follow-up visits scheduled for 60, 100, and 180 days after initial confirmed diagnosis based on typical symptoms and a positive reverse transcription-polymerase chain reaction (RT-PCR) for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). We employed comprehensive pulmonary function and laboratory tests, including serum concentrations of IgG against the viral spike (S) glycoprotein, and compared the results to clinical data and chest computed tomography (CT). We found that at the 60 day follow-up, 131 of 145 (90.3%) participants displayed S-specific serum IgG levels above the cut-off threshold. Notably, the highly elevated IgG levels against S glycoprotein positively correlated with biomarkers of immune activation and negatively correlated with pulmonary function and the extent of pulmonary CT abnormalities. Based on the association between serum S glycoprotein-specific IgG and clinical outcome, we generated an S-specific IgG-based recovery score that, when applied in the early convalescent phase, accurately predicted delayed pulmonary recovery after COVID-19. Therefore, we propose that S-specific IgG levels serve as a useful immunological surrogate marker for identifying at-risk individuals with persistent pulmonary injury who may require intensive follow-up care after COVID-19.

The Comparability of Anti-Spike SARS-CoV-2 Antibody Tests is Time-Dependent: a Prospective Observational Study

Various commercial anti-Spike SARS-CoV-2 antibody tests are used for studies and in clinical settings after vaccination. An international standard for SARS-CoV-2 antibodies has been established to achieve comparability of such tests, allowing conversions to BAU/mL. This study aimed to investigate the comparability of antibody tests regarding the timing of blood collection after vaccination. For this prospective observational study, antibody levels of 50 participants with homologous AZD1222 vaccination were evaluated at 3 and 11 weeks after the first dose and 3 weeks after the second dose using two commercial anti-Spike binding antibody assays (Roche and Abbott) and a surrogate neutralization assay. The correlation between Roche and Abbott changed significantly depending on the time point studied. Although Abbott provided values three times higher than Roche 3 weeks after the first dose, the values for Roche were twice as high as for Abbott 11 weeks after the first dose and 5 to 6 times higher at 3 weeks after the second dose. The comparability of quantitative anti-Spike SARS-CoV-2 antibody tests was highly dependent on the timing of blood collection after vaccination. Therefore, standardization of the timing of blood collection might be necessary for the comparability of different quantitative SARS-COV-2 antibody assays. IMPORTANCE This work showed that the comparability of apparently standardized SARS-CoV-2 antibody assays (Roche, Abbott; both given in BAU/mL) after vaccination depends on the time of blood withdrawal. Initially (3 weeks after the first dose AZD1222), there were 3 times higher values in the Abbott assay, but this relationship inversed before boosting (11 weeks after the first dose) with Roche 2 times greater than Abbott. After the booster, Roche quantified ca. 5 times higher levels than Abbott. This must be considered by clinicians when interpreting SARS-CoV-2 antibody levels.

Incidence of severe breakthrough SARS-CoV-2 infections in vaccinated kidney transplant and haemodialysis patients

Introduction

Given the increased COVID-19 observed in kidney transplant recipients (KTRs) and haemodialysis patients, several studies have tried to establish the efficacy of mRNA vaccines in these populations by evaluating their humoral and cellular responses. However, there is currently no information on clinical protection (deaths and hospitalizations), a gap that this study aims to fill.

Methods

Observational prospective study involving 1,336 KTRs and haemodialysis patients from three dialysis units affiliated to Hospital Clínic of Barcelona, Spain, vaccinated with two doses of mRNA-1273 (Moderna) or BNT162b2 (Pfizer-BioNTech) SARS-CoV-2 mRNA vaccines. The outcomes measured were SARS-CoV-2 infection diagnosed by a positive RT-PCR fourteen days after the second vaccine dose, hospital admissions derived from infection, and a severe COVID-19 composite outcome, defined as either ICU admission, invasive and non-invasive mechanical ventilation, or death.

Results

Six per cent (18/302) of patients on haemodialysis were infected, of whom four required hospital admission (1.3%), only one (0.3%) had severe COVID-19, and none of them died. In contrast, 4.3% (44/1034) of KTRs were infected, and presented more hospital admissions (26 patients, 2.5%), severe COVID-19 (11 patients, 1.1%) or death (4 patients, 0.4%). KTRs had a significantly higher risk of hospital admission than HD patients, and this risk increased with age and male sex (HR 3.37 and 4.74, respectively).

Conclusions

The study highlights the need for booster doses in KTRs. In contrast, the haemodialysis population appears to have an adequate clinical response to vaccination, at least up to four months from its administration.

Graphical abstract

Long-Term Comparison of 7 SARS-CoV-2 Antibody Assays in the North Zealand Covid-19 Cohort

Background

Throughout the coronavirus disease 2019 (Covid-19) pandemic numerous severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody assays have been approved through Emergency Use Authorization and require further evaluation of sensitivity and specificity in clinical laboratory settings prior to implementation.

Methods

We included 1733 samples from 375 PCR-confirmed SARS-CoV-2–positive individuals of the North Zealand Covid-19 Cohort in an 8-month period. We investigated diagnostic sensitivity and specificity against consensus and PCR and interassay agreement over time for 5 SARS-CoV-2 immunoassays [Roche-nucleocapsid (NC)-total, Roche-receptor binding domain (RBD)-total, Siemens-RBD-IgG, Siemens-RBD-total, Thermo Fisher Scientific (TFS)-RBD-IgG] commercially available on automated platforms and 2 ELISA assays (TFS-RBD-total, Wantai-RBD-total).

Results

Early interassay discrepancy in up to 49% of samples decreased steadily during the first 18 days. By day 18, all assays had reached a plateau between 82.3% and 90.5% seropositivity compared to PCR. Assays ranked by closest agreement with the consensus model beyond day 18 (sensitivity/specificity against consensus) were as follows: Roche-RBD-total, 99.8%/100.0%; Wantai-RBD-total, 99.8%/99.7%; Roche-NC-total, 97.8%/100.0%; Siemens-RBD-total, 98.0%/98.7%; TFS-RBD-total, 96.9%/99.7%; TFS-RBD-IgG, 91.5%/100.0%; and Siemens-RBD-IgG, 94.6%/89.9%. We found that 7.8% of PCR-positive patients remained seronegative in all assays throughout the study.

Conclusions

All included assays had sensitivities against consensus >90% past day 18. For the current recommended use of antibody assays to detect former, undocumented Covid-19, our data suggest the use of total antibody assays rather than IgG-specific assays due to higher long-term sensitivity. Finally, a nonresponding subpopulation of 7.8% in our cohort with persistent seronegative results raises concern of a possible substantial number of people with continued low protection following natural SARS-CoV-2 infection.

Borderline and weakly positive antibody levels against the S-protein of SARS-CoV-2 exhibit limited agreement with virus neutralization titres

The presence of neutralizing antibodies against SARS-CoV-2 in a large number of people is – besides cellular immunity – important to overcome the SARS-CoV-2 pandemic. While determination of neutralizing antibodies via virus neutralization tests are laborious, assays to determine the antibody levels serologically are fully automated and widely available. Correlations between these methodologies were recently given by the manufacturers, however performance in samples close to the cut off value have not yet been fully validated.

Thus, we analysed 22 borderline and low positive (<100 BAU/ml) samples and 9 high positive (≥ 100 BAU/ml) from infected and/or vaccinated individuals and compared the SARS-CoV-2 IgG II Quant assay (Abbott), LIAISON SARS-CoV-2 TrimericS IgG (Diasorin), Elecsys Anti-SARS-CoV-2 S (Roche), and SARS-CoV-2 IgG (Siemens) with results obtained from a virus neutralization test.

Based on the cut off values given by Abbott, Diasorin, Roche, and Siemens, the positive serologic results were concordant with the virus neutralization test in 100%, 76%, 88%, and 71%, respectively, while in turn, negative ones were in agreement in 29%, 79%, 93%, and 86%, respectively.

In conclusion, weakly positive, serologic results are challenging to correctly predict the presence of neutralizing antibodies. Our study suggests, that different cut off values (for positivity vs. presence of neutralizing antibodies) could improve the test's performance, but determination thereof requires more samples to be analysed.

Association of a Third Dose of BNT162b2 Vaccine With Incidence of SARS-CoV-2 Infection Among Health Care Workers in Israel

IMPORTANCE

Administration of a BNT162b2 booster dose (Pfizer-BioNTech) to fully vaccinated individuals aged 60 years and older was significantly associated with lower risk of SARS-CoV-2 infection and severe illness. Data are lacking on the effectiveness of booster doses for younger individuals and health care workers.

OBJECTIVE

To estimate the association of a BNT162b2 booster dose with SARS-CoV-2 infections among health care workers who were previously vaccinated with a 2-dose series of BNT162b2.

DESIGN, SETTING, AND PARTICIPANTS

This was a prospective cohort study conducted at a tertiary medical center in Tel Aviv, Israel. The study cohort included 1928 immunocompetent health care workers who were previously vaccinated with a 2-dose series of BNT162b2, and had enrolled between August 8 and 19, 2021, with final follow-up reported through September 20, 2021. Screening for SARS-CoV-2 infection was performed every 14 days. Anti-spike protein receptor binding domain IgG titers were determined at baseline and 1 month after enrollment. Cox regression with time-dependent analysis was used to estimate hazard ratios of SARS-CoV-2 infection between booster-immunized status and 2-dose vaccinated (booster-nonimmunized) status.

EXPOSURES

Vaccination with a booster dose of BNT162b2 vaccine.

MAIN OUTCOMES AND MEASURES

The primary outcome was SARS-CoV-2 infection, as confirmed by reverse transcriptase-polymerase chain reaction.

RESULTS

Among 1928 participants, the median age was 44 years (IQR, 36-52 years) and 1381 were women (71.6%). Participants completed the 2-dose vaccination series a median of 210 days (IQR, 205-213 days) before study enrollment. A total of 1650 participants (85.6%) received the booster dose. During a median follow-up of 39 days (IQR, 35-41 days), SARS-CoV-2 infection occurred in 44 participants (incidence rate, 60.2 per 100 000 person-days); 31 (70.5%) were symptomatic. Five SARS-CoV-2 infections occurred in booster-immunized participants and 39 in booster-nonimmunized participants (incidence rate, 12.8 vs 116 per 100 000 person-days, respectively). In a time-dependent Cox regression analysis, the adjusted hazard ratio of SARS-CoV-2 infection for booster-immunized vs booster-nonimmunized participants was 0.07 (95% CI, 0.02-0.20).

CONCLUSIONS AND RELEVANCE

Among health care workers at a single center in Israel who were previously vaccinated with a 2-dose series of BNT162b2, administration of a booster dose compared with not receiving one was associated with a significantly lower rate of SARS-CoV-2 infection over a median of 39 days of follow-up. Ongoing surveillance is required to assess durability of the findings.

Clinical Utility of Elecsys Anti-SARS-CoV-2 S Assay in COVID-19 Vaccination: An Exploratory Analysis of the mRNA-1273 Phase 1 Trial

Background

The ability to quantify an immune response after vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential. This study assessed the clinical utility of the quantitative Roche Elecsys^® Anti-SARS-CoV-2 S assay (ACOV2S) using samples from the 2019-nCoV vaccine (mRNA-1273) phase 1 trial (NCT04283461).

Methods

Samples from 30 healthy participants, aged 18–55 years, who received two injections with mRNA-1273 at a dose of 25 μg (n=15) or 100 μg (n=15), were collected at Days 1 (first vaccination), 15, 29 (second vaccination), 43 and 57. ACOV2S results (shown in U/mL – equivalent to BAU/mL per the first WHO international standard) were compared with results from ELISAs specific to antibodies against the Spike protein (S-2P) and the receptor binding domain (RBD) as well as neutralization tests including nanoluciferase (nLUC80), live-virus (PRNT80), and a pseudovirus neutralizing antibody assay (PsVNA50).

Results

RBD-specific antibodies were already detectable by ACOV2S at the first time point of assessment (d15 after first vaccination), with seroconversion before in all but two participants (25 μg dose group); all had seroconverted by Day 29. Across all post-baseline visits, geometric mean concentration of antibody levels was 3.27–7.48-fold higher in the 100 μg compared with the 25 μg dose group. ACOV2S measurements were highly correlated with those from RBD ELISA (Pearson’s r=0.938; p<0.0001) and S-2P ELISA (r=0.918; p<0.0001). For both ELISAs, heterogeneous baseline results and smaller increases in antibody levels following the second vs first vaccination compared with ACOV2S were observed. ACOV2S showed absence of any baseline noise indicating high specificity detecting vaccine-induced antibody response. Moderate–strong correlations were observed between ACOV2S and neutralization tests (nLUC80 r=0.933; PsVNA50, r=0.771; PRNT80, r=0.672; all p ≤ 0.0001).

Conclusion

The Elecsys Anti-SARS-CoV-2 S assay (ACOV2S) can be regarded as a highly valuable method to assess and quantify the presence of RBD-directed antibodies against SARS-CoV-2 following vaccination and may indicate the presence of neutralizing antibodies. As a fully automated and standardized method, ACOV2S could qualify as the method of choice for consistent quantification of vaccine-induced humoral response.

The endogenous factors affecting the detection of serum SARS-CoV-2 IgG/IgM antibodies by ELISA

To investigate endogenous interference factors of the detection results of novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgM/IgG. Enzyme-linked immunosorbent assay (ELISA) was used to detect SARS-CoV-2 IgM/IgG in sera of 200 patients without COVID-19 infection, including rheumatoid factor (RF) positive group, antinuclear antibody (ANA) positive group, pregnant women group and normal senior group, with 50 in each group and 100 normal controls. The level of SARS-CoV-2 IgG in pregnant women was significantly higher than that in normal control group (P = 0.000), but there was no significant difference between other groups. The levels of SARS-CoV-2 IgM in pregnant women group, normal senior group, ANA positive group and RF positive group were significantly higher than that in normal control group (P<0.05), with significant higher false positive rates in these groups (P = 0.036, P = 0.004, P = 0.000, vs normal control group). Serum RF caused SARS-CoV-2 IgM false-positive in concentration dependent manner, especially when its concentration was higher than 110.25 IU/L, and urea dissociation test can turn the false positive to negative. ANA, normal seniors, pregnant women and RF can lead to false-positive reactivity of SARS-CoV-2 IgM and/or IgG detected using ELISA. These factors should be considered when SARS-CoV-2 IgM or IgG detection is positive, false positive samples caused by RF positive can be used for urea dissociation test. This article is protected by copyright. All rights reserved.

Evaluation of Humoral Immune Response after SARS-CoV-2 Vaccination Using Two Binding Antibody Assays and a Neutralizing Antibody Assay

Multiple vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been developed and administered to mitigate the coronavirus disease 2019 (COVID-19) pandemic. We assessed the humoral response of BNT162b2 and ChAdOx1 nCoV-19 using Siemens SARS-CoV-2 IgG (sCOVG; cutoff of ≥1.0 U/ml), Abbott SARS-CoV-2 IgG II Quant (CoV-2 IgG II; cutoff of ≥50.0 AU/ml), and GenScript cPASS SARS-CoV-2 neutralization antibody detection kits (cPASS; cutoff of ≥30% inhibition). We collected 710 serum samples (174 samples after BNT162b2 and 536 samples after ChAdOx1 nCoV-19). Venous blood was obtained 3 weeks after first and second vaccinations. In both vaccines, sCOVG, CoV-2 IgG II, and cPASS showed a high seropositive rate (>95.7%) except for cPASS after the first vaccination with ChAdOx1 nCoV-19 (68.8%). Using sCOVG and CoV-2 IgG II, the ratios of antibody value (second/first) increased 10.6- and 11.4-fold in BNT162b2 (first 14.1, second 134.8 U/ml; first 1,416.2, second 14,326.4 AU/ml) and 2.3- and 2.0-fold in ChAdOx1 nCoV-19 (first 4.0, second 9.1 U/ml; first 431.0, second 9,744.0 AU/ml). cPASS-positive results indicated a very high concordance rate with sCOVG and CoV-2 IgG II (>98%), whereas cPASS-negative results showed a relatively low concordance rate (range of 22.2% to 66.7%). To predict cPASS positivity, we suggested additional cutoffs for sCOVG and CoV-2 IgG II at 2.42 U/ml and 284 AU/ml, respectively. In conclusion, BNT162b2 and ChAdOx1 nCoV-19 evoked robust humoral responses. sCOVG and CoV-2 IgG II showed a very strong correlation with cPASS. sCOVG and CoV-2 IgG II may predict the presence of neutralizing antibodies against SARS-CoV-2. IMPORTANCE The Siemens severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG (sCOVG; Siemens Healthcare Diagnostics Inc., NY, USA) and Abbott SARS-CoV-2 IgG II Quant (CoV-2 IgG II; Abbott Laboratories, Sligo, Ireland), which are automated, quantitative SARS-CoV-2-binding antibody assays, have been recently launched. This study aimed to evaluate the humoral immune response of BNT162b2 and ChAdOx1 nCoV-19 vaccines using sCOVG and CoV-2 IgG II and compare the quantitative values with the results of the GenScript surrogate virus neutralization test (cPASS; GenScript, USA Inc., NJ, USA). Our findings demonstrated that both BNT162b2 and ChAdOx1 nCoV-19 elicited a robust humoral response after the first vaccination and further increased after the second vaccination. sCOVG and CoV-2 IgG II showed a strong correlation, and the concordance rates among sCOVG, CoV-2 IgG II, and cPASS were very high in the cPASS-positive results. The additional cutoff sCOVG and CoV-2 IgG II could predict the results of cPASS.

Seroprevalence of IgG antibodies against SARS-CoV-2 among the general population and healthcare workers in India, June-July 2021: A population-based cross-sectional study

BACKGROUND

India began COVID-19 vaccination in January 2021, initially targeting healthcare and frontline workers. The vaccination strategy was expanded in a phased manner and currently covers all individuals aged 18 years and above. India experienced a severe second wave of COVID-19 during March-June 2021. We conducted a fourth nationwide serosurvey to estimate prevalence of SARS-CoV-2 antibodies in the general population aged ≥6 years and healthcare workers (HCWs).

METHODS AND FINDINGS

We did a cross-sectional study between 14 June and 6 July 2021 in the same 70 districts across 20 states and 1 union territory where 3 previous rounds of serosurveys were conducted. From each district, 10 clusters (villages in rural areas and wards in urban areas) were selected by the probability proportional to population size method. From each district, a minimum of 400 individuals aged ≥6 years from the general population (40 individuals from each cluster) and 100 HCWs from the district public health facilities were included. The serum samples were tested for the presence of IgG antibodies against S1-RBD and nucleocapsid protein of SARS-CoV-2 using chemiluminescence immunoassay. We estimated the weighted and test-adjusted seroprevalence of IgG antibodies against SARS-CoV-2, along with 95% CIs, based on the presence of antibodies to S1-RBD and/or nucleocapsid protein. Of the 28,975 individuals who participated in the survey, 2,892 (10%) were aged 6-9 years, 5,798 (20%) were aged 10-17 years, and 20,285 (70%) were aged ≥18 years; 15,160 (52.3%) participants were female, and 21,794 (75.2%) resided in rural areas. The weighted and test-adjusted prevalence of IgG antibodies against S1-RBD and/or nucleocapsid protein among the general population aged ≥6 years was 67.6% (95% CI 66.4% to 68.7%). Seroprevalence increased with age (p < 0.001) and was not different in rural and urban areas (p = 0.822). Compared to unvaccinated adults (62.3%, 95% CI 60.9% to 63.7%), seroprevalence was significantly higher among individuals who had received 1 vaccine dose (81.0%, 95% CI 79.6% to 82.3%, p < 0.001) and 2 vaccine doses (89.8%, 95% CI 88.4% to 91.1%, p < 0.001). The seroprevalence of IgG antibodies among 7,252 HCWs was 85.2% (95% CI 83.5% to 86.7%). Important limitations of the study include the survey design, which was aimed to estimate seroprevalence at the national level and not at a sub-national level, and the non-participation of 19% of eligible individuals in the survey.

CONCLUSIONS

Nearly two-thirds of individuals aged ≥6 years from the general population and 85% of HCWs had antibodies against SARS-CoV-2 by June-July 2021 in India. As one-third of the population is still seronegative, it is necessary to accelerate the coverage of COVID-19 vaccination among adults and continue adherence to non-pharmaceutical interventions.

Clinical Evaluation of Siemens SARS-CoV-2 Total Antibody assay and IgG assay using the Dimension EXL 200 in the Tokyo Metropolitan area

BACKGROUND

We evaluated the efficacy of the Siemens SARS-CoV-2 Total Antibody assay (CV2T) and IgG assay (CV2G) that can detect antibodies against the receptor binding domain of S antigen in patients with COVID-19 in a Tokyo metropolitan area.

METHODS

Sensitivity and antibody levels were examined by CV2T and CV2G on Dimension EXL 200 using 236 serum samples obtained from 79 RT-PCR confirmed COVID-19 patients at multiple time points and were compared with disease severity by the World Health Organization criteria. The assay specificity was evaluated using samples collected before the COVID-19 pandemic.

RESULTS

The sensitivity of CV2T and CV2G were low (16.7-21.4%) in days 0-6 and increased to 43.8-52.5% in days 7-13 and to 80.8-90.0% in days 14-20. The seroprevalences persisted after day 21 to days past 42 regardless of disease severity. In every day grouping, mean antibody levels were higher in severe cases than in mild cases with a significant difference in days 14-20 and days 20-27. The specificity was 97.9 % (95% CI; 92.8-99.8) for CV2T and 99.0 % (95% CI; 94.6-100) for CV2G.

CONCLUSIONS

Our results indicate a high specificity and high sensitivity at 14 days of CV2T and CV2G as antibody detection assays.

Evaluation of commercial anti-SARS-CoV-2 antibody assays and comparison of standardized titers in vaccinated healthcare workers

With the availability of vaccines, commercial assays detecting anti-severe acute respiratory syndrome coronavirus-2 antibodies (Ab) evolved toward quantitative assays directed to the spike glycoprotein or its receptor binding domain (RBD). The main objective of the present study was to compare the Ab titers obtained with quantitative commercial binding Ab assays, after one dose (convalescent individuals) or two doses (naive individuals) of vaccine, in health care workers (HCW). Antibody titers were measured in 255 sera (from 150 HCW) with five quantitative immunoassays (Abbott RBD IgG II quant, bioMérieux RBD IgG, DiaSorin Trimeric spike IgG, Siemens Healthineers RBD IgG, Wantai RBD IgG). One qualitative total antibody anti-RBD detection assay (Wantai) was used to detect previous infection before vaccination. The results are presented in binding Ab units (BAU)/mL after application, when possible, of a conversion factor provided by the manufacturers and established from a World Health Organization internal standard. There was a 100% seroconversion with all assays evaluated after two doses of vaccine. With assays allowing BAU/mL correction, Ab titers were correlated (Pearson correlation coefficient, ρ, range: 0.85–0.94). The titer differences varied by a mean of 10.6% between Siemens and bioMérieux assays to 60.9% between Abbott and DiaSorin assays. These results underline the importance of BAU conversion for the comparison of Ab titer obtained with the different quantitative assays. However, significant differences persist, notably, between kits detecting Ab against the different antigens. A true standardization of the assays would be to include the International Standard in the calibration of each assay to express the results in IU/mL.

Clinical utility of Elecsys Anti-SARS-CoV-2 S assay in COVID-19 vaccination: An exploratory analysis of the mRNA-1273 phase 1 trial

Background

The ability to quantify an immune response after vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential. This study assessed the clinical utility of the quantitative Roche Elecsys^® Anti-SARS-CoV-2 S assay (ACOV2S) using samples from the 2019-nCoV vaccine (mRNA-1273) phase 1 trial (NCT04283461).

Methods

Samples from 30 healthy participants, aged 18–55 years, who received two injections with mRNA-1273 at a dose of 25 μg (n=15) or 100 μg (n=15), were collected at Days 1 (first vaccination), 15, 29 (second vaccination), 43 and 57. ACOV2S results (shown in U/mL – equivalent to BAU/mL per the first WHO international standard) were compared with results from ELISAs specific to antibodies against the Spike protein (S-2P) and the receptor binding domain (RBD) as well as neutralization tests including nanoluciferase (nLUC₈₀), live-virus (PRNT₈₀), and a pseudovirus neutralizing antibody assay (PsVNA₅₀).

Results

RBD-specific antibodies were already detectable by ACOV2S at the first time point of assessment (d15 after first vaccination), with seroconversion before in all but 2 participants (25 μg dose group); all had seroconverted by Day 29. Across all post-baseline visits, geometric mean concentration of antibody levels were 3.27–7.48-fold higher in the 100 μg compared with the 25 μg dose group. ACOV2S measurements were highly correlated with those from RBD ELISA (Pearson’s r=0.938; p<0.0001) and S-2P ELISA (r=0.918; p<0.0001). For both ELISAs, heterogeneous baseline results and smaller increases in antibody levels following the second vs first vaccination compared with ACOV2S were observed. ACOV2S showed absence of any baseline noise indicating high specificity detecting vaccine-induced antibody response. Moderate–strong correlations were observed between ACOV2S and neutralization tests (nLUC₈₀ r=0.933; PsVNA₅₀, r=0.771; PRNT₈₀, r=0.672; all p≤0.0001).

Conclusion

The Elecsys Anti-SARS-CoV-2 S assay (ACOV2S) can be regarded as a highly valuable method to assess and quantify the presence of RBD-directed antibodies against SARS-CoV-2 following vaccination, and may indicate the presence of neutralizing antibodies. As a fully automated and standardized method, ACOV2S could qualify as the method of choice for consistent quantification of vaccine-induced humoral response.

Reduced humoral immune response after BNT162b2 coronavirus disease 2019 messenger RNA vaccination in cancer patients under antineoplastic treatment

Background

Cancer patients are at a higher risk of developing severe coronavirus disease 2019 (COVID-19). However, the safety and efficacy of COVID-19 vaccination in cancer patients undergoing treatment remain unclear.

Patients and methods

In this interventional prospective multicohort study, priming and booster doses of the BNT162b2 COVID-19 vaccine were administered 21 days apart to solid tumor patients receiving chemotherapy, immunotherapy, targeted or hormonal therapy, and patients with a hematologic malignancy receiving rituximab or after allogeneic hematopoietic stem cell transplantation. Vaccine safety and efficacy (until 3 months post-booster) were assessed. Anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) receptor-binding domain (RBD) antibody levels were followed over time (until 28 days after the booster) and in vitro SARS-CoV-2 50% neutralization titers (NT50) toward the wild-type Wuhan strain were analyzed 28 days after the booster.

Results

Local and systemic adverse events (AEs) were mostly mild to moderate (only 1%-3% of patients experienced severe AEs). Local, but not systemic, AEs occurred more frequently after the booster dose. Twenty-eight days after the booster vaccination of 197 cancer patients, RBD-binding antibody titers and NT50 were lower in the chemotherapy group {234.05 IU/ml [95% confidence interval (CI) 122.10-448.66] and 24.54 (95% CI 14.50-41.52), respectively} compared with healthy individuals [1844.93 IU/ml (95% CI 1383.57-2460.14) and 122.63 (95% CI 76.85-195.67), respectively], irrespective of timing of vaccination during chemotherapy cycles. Extremely low antibody responses were seen in hematology patients receiving rituximab; only two patients had RBD-binding antibody titers necessary for 50% protection against symptomatic SARS-CoV-2 infection (<200 IU/ml) and only one had NT50 above the limit of detection. During the study period, five cancer patients tested positive for SARS-CoV-2 infection, including a case of severe COVID-19 in a patient receiving rituximab, resulting in a 2-week hospital admission.

Conclusion

The BNT162b2 vaccine is well-tolerated in cancer patients under active treatment. However, the antibody response of immunized cancer patients was delayed and diminished, mainly in patients receiving chemotherapy or rituximab, resulting in breakthrough infections.

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The BNT162b2 vaccine is well-tolerated in cancer patients, including patients under immunotherapy.

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Full BNT162b2 vaccination results in a blunted humoral immune response in cancer patients under active treatment.

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The humoral immune response after BNT162b2 vaccination varies between different antineoplastic treatments.

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Two doses of BNT162b2 vaccination may insufficiently protect patients receiving chemotherapy or rituximab against SARS-CoV-2.

Humoral and Cellular Responses to mRNA-1273 and BNT162b2 SARS-CoV-2 Vaccines Administered to Hemodialysis Patients

RATIONALE & OBJECTIVE

Patients with kidney failure who are receiving maintenance dialysis have a higher risk of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and worse clinical outcomes after coronavirus disease 2019 (COVID-19) than the general population. Therefore, immunization against SARS-CoV-2 with effective vaccines is an important component of health-maintenance strategies for these patients. This study evaluated the humoral and cellular responses to messenger RNA (mRNA) SARS-CoV-2 vaccines in this population.

STUDY DESIGN

Observational prospective multicenter cohort study.

SETTING & PARTICIPANTS

205 patients treated at 3 dialysis units at the Hospital Clínic of Barcelona (Spain) were vaccinated from February 3 to April 4, 2021, and followed until April 23, 2021.

EXPOSURE

Immunization with either the mRNA-1273 (Moderna) or BNT162b2 (Pfizer-BioNTech) SARS-CoV-2 mRNA vaccine.

OUTCOME

Seroconversion, defined as the detection of IgG antibodies to the receptor-binding domain of the S1 spike antigen of SARS-CoV-2 (anti-S1-RBD IgG), and the identification of activated CD4+T cells 3 weeks after completing vaccination. Anti-S1-RBD IgG levels were also analyzed as a secondary outcome.

ANALYTICAL APPROACH

Univariate and multivariable logistic and multiple linear regression models were used to evaluate the associations between vaccination and study outcomes.

RESULTS

We found that 97.7% of 175 vaccinated patients who were seronegative at baseline developed a response (humoral, cellular, or both); 95.4% of these patients seroconverted, while 62% of those tested for cellular immunity had a positive response. Greater age and immunosuppressive treatment were associated with lower antibody levels.

LIMITATIONS

Mandatory vaccine administration by health authorities. Anti-S1-RBD IgG levels were reported up to 150U/mL and cellular immune responses were characterized qualitatively. Antibody assay and cellular response assessment may not be comparable with previously published laboratory approaches.

CONCLUSIONS

Immunization with mRNA vaccines generated a humoral and cellular immune response in a high proportion of patients with kidney failure receiving maintenance dialysis. These findings as well as the high risk of infection and poor clinical outcomes among these patients make their vaccination a health priority.

Comparative Immunogenicity of BNT162b2 mRNA Vaccine with Natural SARS-CoV-2 Infection

BNT162b2 has proven to be highly effective, but there is a paucity of data regarding immunogenicity factors and comparison between response to vaccination and natural infection. This study included 871 vaccinated healthcare workers (HCW) and 181 patients with natural infection. Immunogenicity was assessed by measuring anti-SARS-CoV-2 against the RBD domain of the spike protein (anti-RBD). Samples were collected 1-2 weeks after vaccination or 15-59 days post-onset of symptoms. Post-vaccine anti-RBD concentrations were associated with age, gender, vaccination side-effects (VSE) and prior infection (Pr-CoV). Anti-RBD median levels (95%CI) were lower by 2466 (651-5583), 6228 (3254-9203) and 7651 (4479-10,823) AU/mL in 35-44, 45-54, 55-70 yrs, respectively, compared with the 18-34 yrs group. In females, the median levels were higher by 2823 (859-4787), 5024 (3122-6926) in individuals with VSE, and 9971 (5158-14,783) AU/mL in HCWs with Pr-CoV. The ratio of anti-RBD in vaccinated individuals versus those with natural infection varied from 1.0 to 19.4. The high immunogenicity of BNT162b2 is verified, although its sustainability has yet to be elucidated. The use of comparative data from natural infection serological panels, expressing the clinical heterogeneity of natural infection, may facilitate early decisions for candidate vaccines to be evaluated in clinical trials.