Side-by-Side Comparison of Three Fully Automated SARS-CoV-2 Antibody Assays with a Focus on Specificity

Dynamics of serum cross-neutralization capacity against SARS-CoV-2 Delta variant in convalescent COVID-19 patients

The magnitude and breadth of the neutralizing antibody response against variants of concern following natural infection would provide valuable insights regarding the immune response induced by severe acute respiratory syndrome-related coronavirus (SARS-CoV-2) infection. Herein, 25 patients were followed at 30 ±7 (Visit 1), 90± 15 (Visit 2), and 180 ± 15 (Visit 3) days post symptom onset (PSO). The neutralization titers against both Wuhan-Hu-1 (WT) and Delta variant were analyzed in parallel along with anti-Spike antibodies (anti-S1/S2 immunoglobulin G [IgG]). The median values of half-maximal neutralization titer (NT50 ) for the WT and Delta variants decreased by 75.8% and 82.2% at Visit 2 and by 85.4% and 81.4% at Visit 3, respectively. At Visit 1, the correlation between the anti-S1/S2 IgG and Nabs titers for the Delta variant was moderate for WT (r = 0.58) and weak for the Delta variant (r = 0.39). However, the correlation coefficient consistently remained above 0.7, with a very strong correlation at Visit 3 for both WT and Delta variants (r = 0.81). The dynamics of anti-S1/S2 IgG antibodies, NT50 , and cross-neutralization index correlated at different time points PSO. Longitudinal analysis of the cross-neutralization capacity of immune sera will inform upon the durability of the immune response against SARS CoV-2 variants.

The changing profile of SARS-CoV-2 serology in Irish blood donors

Background

The present study aimed to investigate the progression of the SARS-CoV-2 pandemic in Ireland over the first three waves of infection.

Method

A selection of blood donor serum samples collected between February 2020 and December 2021 were analysed by various commercially available serological assays for antibodies to SARS-CoV-2 (n = 15,066).

Results

An increase in seropositivity was observed between wave 1 (February to September 2020) and wave 2 (November and December 2020) of 2.20% to 3.55%. A large increase in estimated seroprevalence to 11.89% was observed in samples collected in February and March 2021 (wave 3 of infection).The rate of seropositivity varied by age group, with the highest rate observed in the youngest donors (18-29 years) peaking at 18.79% in wave 3. The results of spike antibody (anti-S) testing indicated that 44/1009 (4.36%) of seroreactive donors in wave 3 had a serological profile consistent with vaccination. By November 2021, we detected an overall seropositivity of 97.04%.

Conclusions

The present study provides a comprehensive estimation of the level of circulating SARS-CoV-2 antibodies in Irish blood donors, enabling differentiation between vaccination and natural infection, as well as real-time monitoring of the progression of the COVID-19 pandemic in Ireland. Seroepidemiology has a role in determining reliable estimates of transmission, infection fatality rates and vaccine uptake. The continued screening of blood donors for this purpose has the potential to generate important data to assist with the management of future waves of SARS-CoV-2.

Association between reactogenicity and immunogenicity after BNT162b2 booster vaccination: a secondary analysis of a prospective cohort study

OBJECTIVES

A weak correlation between symptom severity and antibody levels after primary immunization against COVID-19 has already been shown. This study aimed to describe the association between reactogenicity and immunogenicity after booster vaccination.

METHODS

This secondary analysis of a prospective cohort study included 484 healthcare workers who received a booster vaccination with BNT162b2. Anti-receptor binding domain (RBD) antibodies were assessed at baseline and 28 days after booster vaccination. Side effects were graded (none, mild, moderate, or severe) and reported daily for 7 days after booster vaccination. Spearman correlation coefficient (rho) was used to determine the correlations between the severity of each symptom and anti-RBD levels before vaccination and 28 days after. The Bonferroni method was used to adjust p values for multiple comparisons.

RESULTS

Most of the 484 participants reported at least one local (451 [93.2%]) or systemic (437 [90.3%]) post-booster symptom. No correlations between the severity of local symptoms and antibody levels were found. Except for nausea, systemic symptoms showed weak but statistically significant correlations with 28-day anti-RBD levels (fatigue [rho = 0.23, p < 0.01], fever [rho = 22, p < 0.01], headache [rho = 0.15, p 0.03], arthralgia [rho = 0.2, p < 0.01], myalgia [rho = 0.17, p < 0.01]). There was no association between post-booster symptoms and pre-booster antibody levels.

DISCUSSION

This study showed only a weak correlation between the severity of systemic post-booster symptoms and anti-SARS-CoV-2 antibody levels at 28 days. Therefore, self-reported symptom severity cannot be used to predict immunogenicity after booster vaccination.

Assessment of mRNA Vaccine Immunogenicity in Solid Organ Transplant Recipients

Background and Objectives: Solid organ transplant (SOT) recipients have a higher risk of suffering from severe Coronavirus (COVID-19) compared to the general population. Studies have shown impaired immunogenicity of mRNA vaccines in this high-risk population; thus, SOT recipients have been prioritized globally for primary and booster doses. Materials and Methods: We analyzed 144 SOT recipients who had previously received two doses of BNT162b2 or mRNA1273 vaccine, and who were subsequently vaccinated with a booster dose of the mRNA1273 vaccine. Humoral and cellular immune responses were measured 1 and 3 months after the second dose, and 1 month after the third dose. Results: One month after the second dose, 33.6% (45/134) of patients displayed a positive antibody response with a median (25th, 75th) antibody titer of 9 (7, 161) AU/mL. Three months after the second dose, 41.8% (56/134) tested positive with a median (25th, 75th) antibody titer of 18 (7, 251) AU/mL. After the booster dose, the seropositivity rate increased to 69.4% (93/134), with a median (25th, 75th) titer of 966 (10, 8027) AU/mL. The specific SARS-CoV-2 T-cell response was assessed in 44 randomly selected recipients 3 months after the second dose, and 11.4% (5/44) of them had a positive response. Following the third dose, 42% (21/50) tested positive. Side effects after the third dose were mild, with pain at the injection site being the most frequent adverse effect, reported by 73.4% of the recipients. Conclusion: Our study shows a mild delayed increase in antibody titer, three months after primary vaccination compared to one month after. It also shows a robust augmentation of humoral and specific T-cell responses after the booster dose, as well as the safety and tolerability of the mRNA vaccines in SOT recipients.

Disease Course, Management and Outcomes in Kidney Transplant Recipients with SARS-CoV-2 Infection during the Omicron-Variant Wave: A Single-Center Experience

Background: Since December 2019, kidney transplant recipients (KTRs) have experienced a great impact of the coronavirus disease 2019 (COVID-19) pandemic, with a higher risk of morbidity and mortality compared to the general population. Preliminary data in KTRs suggest that the Omicron variant, which has been dominant since December 2021, is more infectious than the previous ones but is associated with reduced risk of severity and low lethality rates. The purpose of our study was to assess the disease course and outcomes of the SARS-CoV-2 infection in KTRs during the Omicron-surge. Methods: This retrospective study included 451 KTRs diagnosed with SARS-CoV-2 infection between 1 December 2021 and 30 September 2022. Demographic and clinical characteristics at the time of infection, vaccination data, treatment, clinical course, and outcomes were recorded and analyzed. Results: Mean age was 51.8 ± 13.7 years with a male predominance (61.2%). The majority (76.1%) were vaccinated with at least three doses of the available mRNA vaccines, although serology revealed low anti-SARS-CoV-2 antibody titers before infection (33 [3.3–1205] AU/mL). Only 6% of the patients experienced moderate–severe disease. Accordingly, there was low prevalence of adverse outcomes, such as SARS-CoV-2-related hospitalization (11.3%) and death (0.9%). Multivariate analysis revealed that only age significantly increased the risk of SARS-CoV-2-related hospitalization. Conclusions: During the Omicron wave, the clinical course of the SARS-CoV-2 infection in KTRs has substantially changed, with lower rates of moderate and severe disease and a low prevalence of adverse outcomes. Prospective clinical trials are warranted to further elucidate the evolving pathogenesis, management, and long-term outcomes of COVID-19 in such high-risk populations.

Lessons learned: A look back at the performance of nine COVID-19 serologic assays and their proposed utility

BACKGROUND

Serologic assays for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been proposed to assist with the acute diagnosis of infection, support epidemiological studies, identify convalescent plasma donors, and evaluate vaccine response.

METHODS

We report an evaluation of nine serologic assays: Abbott (AB) and Epitope (EP) IgG and IgM, EUROIMMUN (EU) IgG and IgA, Roche anti-N (RN TOT) and anti-S (RS TOT) total antibody, and DiaSorin (DS) IgG. We evaluated 291 negative controls (NEG CTRL), 91 PCR positive (PCR POS) patients (179 samples), 126 convalescent plasma donors (CPD), 27 healthy vaccinated donors (VD), and 20 allogeneic hematopoietic stem cell transplant (HSCT) recipients (45 samples).

RESULTS

We observed good agreement with the method performance claims for specificity (93-100%) in NEG CTRL but only 85% for EU IgA. The sensitivity claims in the first 2 weeks of symptom onset was lower (26-61%) than performance claims based on > 2 weeks since PCR positivity. We observed high sensitivities (94-100%) in CPD except for AB IgM (77%), EP IgM (0%). Significantly higher RS TOT was observed for Moderna vaccine recipients then Pfizer (p-values < 0.0001). A sustained RS TOT response was observed for the five months following vaccination. HSCT recipients demonstrated significantly lower RS TOT than healthy VD (p < 0.0001) at dose 2 and 4 weeks after.

CONCLUSIONS

Our data suggests against the use of anti-SARS-CoV-2 assays to aid in acute diagnosis. RN TOT and RS TOT can readily identify past-resolved infection and vaccine response in the absence of native infection. We provide an estimate of expected antibody response in healthy VD over the time course of vaccination for which to compare antibody responses in immunosuppressed patients.

Multiparametric Prediction Models for Coronavirus Disease 2019 Vaccine Selection: Results of a Comparative Population-Based Cohort Study

BACKGROUND

An understanding vaccine-dependent effects on protective and sustained humoral immune response is crucial to planning future vaccination strategies against coronavirus disease 2019 (COVID-19).

METHODS

In this multicenter, population-based, cohort study including 4601 individuals after primary vaccination against COVID-19 ≥ 4 months earlier we compared factors associated with residual antibody levels against severe acute respiratory syndrome coronavirus-2 receptor-binding domain (RBD) across different vaccination strategies (BNT162b2, mRNA-1273, or ChAdOx1).

RESULTS

Our main model including 3787 individuals (2 × BNT162b2, n = 2271; 2 × mRNA-1273, n = 251; 2 × ChAdOx1, n = 1265), predicted significantly lower levels of anti-RBD antibodies after 6 months in individuals vaccinated with ChAdOx1 (392.7 binding antibody units per milliliter [BAU/mL]) compared with those vaccinated with BNT162b2 (1179.5 BAU/mL) or mRNA-1273 (2098.2 BAU/mL). Vaccine-dependent association of antibody levels was found for age with a significant predicted difference in BAU/ml per year for BNT162b2 (-21.5; 95% confidence interval [CI], -24.7 to -18.3) and no significant association for mRNA-1273 (-4.0; 95% CI, -20.0 to 12.1) or ChAdOx1 (1.7; 95% CI, .2 to 3.1). The predicted decrease over time since full immunization was highest in mRNA-1273 (-23.4; 95% CI, -31.4 to -15.4) compared with BNT162b2 (-5.9; 95% CI, -7 to -4.8).

CONCLUSIONS

Our study revealed population-based evidence of vaccine-dependent effects of age and time since full immunization on humoral immune response. Findings underline the importance of individualized vaccine selection, especially in elderly individuals.

The accelerated waning of immunity and reduced effect of booster in patients treated with bDMARD and tsDMARD after SARS-CoV-2 mRNA vaccination

Objectives

This study aimed to assess the duration of humoral responses after two doses of SARS-CoV-2 mRNA vaccines in patients with inflammatory joint diseases and IBD and booster vaccination compared with healthy controls. It also aimed to analyze factors influencing the quantity and quality of the immune response.

Methods

We enrolled 41 patients with rheumatoid arthritis (RA), 35 with seronegative spondyloarthritis (SpA), and 41 suffering from inflammatory bowel disease (IBD), excluding those receiving B-cell-depleting therapies. We assessed total anti-SARS-CoV-2 spike antibodies (Abs) and neutralizing Ab titers 6 months after two and then after three doses of mRNA vaccines compared with healthy controls. We analyzed the influence of therapies on the humoral response.

Results

Patients receiving biological or targeted synthetic disease-modifying antirheumatic drugs (b/tsDMARDs) showed reduced anti-SARS-CoV-2 S Abs and neutralizing Ab titers compared with HC or patients receiving conventional synthetic (cs)DMARDs 6 months after the first two vaccination doses. Anti-SARS-CoV-2 S titers of patients with b/tsDMARDs declined more rapidly, leading to a significant reduction in the duration of vaccination-induced immunity after two doses of SARS-CoV-2 mRNA vaccines. While 23% of HC and 19% of patients receiving csDMARDs were without detectable neutralizing Abs 6 months after the first two vaccination doses, this number was 62% in patients receiving b/tsDMARDs and 52% in patients receiving a combination of csDMARDs and b/tsDMARDs. Booster vaccination led to increased anti-SARS-CoV-2 S Abs in all HC and patients. However, anti-SARS-CoV-2 S Abs after booster vaccination was diminished in patients receiving b/tsDMARDs, either alone or in combination with csDMARDs compared to HC.

Conclusion

Patients receiving b/tsDMARDs have significantly reduced Abs and neutralizing Ab titers 6 months after mRNA vaccination against SARS-CoV-2. This was due to a faster decline in Ab levels, indicating a significantly reduced duration of vaccination-induced immunity compared with HC or patients receiving csDMARDs. In addition, they display a reduced response to a booster vaccination, warranting earlier booster vaccination strategies in patients under b/tsDMARD therapy, according to their specific Ab levels.

Comparison of one single-antigen assay and three multi-antigen SARS-CoV-2 IgG assays in Nigeria

Objectives

Determining an accurate estimate of SARS-CoV-2 seroprevalence has been challenging in African countries where malaria and other pathogens are endemic. We compared the performance of one single-antigen assay and three multi-antigen SARS-CoV-2 IgG assays in a Nigerian population endemic for malaria.

Methods

De-identified plasma specimens from SARS-CoV-2 RT-PCR positive, dried blood spot (DBS) SARS-CoV-2 RT-PCR positive, and pre-pandemic negatives were used to evaluate the performance of the four SARS-CoV-2 assays (Tetracore, SARS2MBA, RightSign, xMAP).

Results

Results showed higher sensitivity with the multi-antigen (81% (Tetracore), 96% (SARS2MBA), 85% (xMAP)) versus the single-antigen (RightSign (64%)) SARS-CoV-2 assay. The overall specificities were 98% (Tetracore), 100% (SARS2MBA and RightSign), and 99% (xMAP). When stratified based on <15 days to ≥15 days post-RT-PCR confirmation, the sensitivities increased from 75% to 88.2% for Tetracore; from 93% to 100% for the SARS2MBA; from 58% to 73% for RightSign; and from 83% to 88% for xMAP. With DBS, there was no positive increase after 15-28 days for the three assays (Tetracore, SARS2MBA, and xMAP).

Conclusion

Multi-antigen assays performed well in Nigeria, even with samples with known malaria reactivity, and might provide more accurate measures of COVID-19 seroprevalence and vaccine efficacy.

Preanalytical stability of SARS-CoV-2 anti-nucleocapsid antibodies

OBJECTIVES

Anti-nucleocapsid (NC) antibodies are produced in response to SARS-CoV-2 infection. Therefore, they are well suited for the detection of a previous infection. Especially in the case of seroprevalence studies or during the evaluation of a novel in-vitro diagnostic test, samples have been stored at <-70 °C (short- and long-term) or 2-10 °C (short-term) before analysis. This study aimed to assess the impact of different storage conditions relevant to routine biobanking on anti-NC antibodies.

METHODS

The preanalytical impact of short-term storage (84 [58-98] days) on <-70 °C and for 14 days at 2-10 °C was evaluated using samples from 111 donors of the MedUni Vienna Biobank. Long-term effects (443 [409-468] days) were assessed using 208 samples from Biobank Graz and 49 samples from Biobank Vienna. Anti-Nucleocapsid antibodies were measured employing electrochemiluminescence assays (Roche Anti-SARS-CoV-2).

RESULTS

After short-term storage, the observed changes did not exceed the extent that could be explained by analytical variability. In contrast, results after long-term storage were approximately 20% higher and seemed to increase with storage duration. This effect was independent of the biobank from which the samples were obtained. Accordingly, the sensitivity increased from 92.6 to 95.3% (p=0.008). However, comparisons with data from Anti-Spike protein assays, where these deviations were not apparent, suggest that this deviation could also be explained by the analytical variability of the qualitative Anti-NC assay.

CONCLUSIONS

Results from anti-NC antibodies are stable during short-term storage at <-70 °C and 2-10 °C. After long-term storage, a slight increase in sensitivity could not be ruled out.

Comparison of five Anti-SARS-CoV-2 antibody assays across three doses of BNT162b2 reveals insufficient standardization of SARS-CoV-2 serology

OBJECTIVES

To investigate the comparability of WHO standard referenced commercial SARS-CoV-2 antibody tests over three doses of BNT162b2 vaccine and up to 14 months.

METHODS

114 subjects (without previous SARS-CoV-2 infection or immunosuppressive medication) vaccinated with three doses of BNT162b2 were included in this study. Antibody levels were quantified 3 weeks after the first dose, 5-6 weeks and 7 months after the second dose, and 4-5 weeks and 4 months after the third dose using the Roche Elecsys SARS-CoV-2 S, the Abbott SARS-CoV-2 IgG II Quant, the DiaSorin LIAISON SARS-CoV-2 TrimericS IgG, the GenScript cPASS sVNT and the TECO sVNT assays.

RESULTS

For each time point analyzed, systematic differences are evident between the results in BAU/mL of the three antibody binding assays. The assay ratios change in a time-dependent manner even beyond administering the third dose (Roche measuring 9 and 3 times higher than Abbott and DiaSorin, respectively). However, changes decrease in magnitude with increasing time intervals from the first dose. IgG-based assays show better agreement across them than with Roche (overall correlations: Abbott x DiaSorin: ρ = 0.94 vs. Abbott x Roche: ρ=0.89, p < 0.0001; DiaSorin x Roche: ρ = 0.87, p < 0.0001), but results are not interchangeable. The sVNTs suggest an underestimation of antibody levels by Roche and slight overestimation by both IgG assays after the first vaccine dose.

CONCLUSIONS

Standardization of SARS-CoV-2 antibody binding assays still needs to be improved to allow reliable use of variable assay systems for longitudinal analyses.

Immunogenicity of the Two mRNA SARS-CoV-2 Vaccines in a Large Cohort of Dialysis Patients

Chronic kidney disease patients, especially those on hemodialysis, are at the highest risk of a severe course and death from COVID-19. Moreover, they appear to have suboptimal response in both cellular and humoral immunity after vaccination. The present study investigated humoral and cellular response and safety after two doses of either of the two authorized mRNA vaccines in a cohort of 310 patients on maintenance dialysis. The antibody response rate was 94.5%, with a median (25th, 75th) antibody titer of 3478 (1236, 8141) AU/mL. Only mild adverse effects were observed. Only vaccine type was independently associated with immunogenicity. Α statistically significant difference in favor of mRNA1273 versus BNT162b2 vaccine was observed. Antibody positivity (100% vs. 94.3%, p < 0.001), median (25th, 75th) antibody levels: 9499 (6118, 20,780) AU/mL vs. 3269 (1220, 7807) AU/mL (p < 0.001). Among the 65 patients tested for T-cell response, 27 (41.5%) had a positive one with a median (25th, 75th) antibody titer of 6007 (3405, 12,068) AU/mL, while 38 with no T-cell response presented a lower median (25th, 75th) antibody titer of 1744 (850, 4176) AU/mL (p < 0.001). Both mRNA vaccines are safe for dialysis patients and can trigger humoral and cellular responses, although with lower titers than those that have been reported to healthy individuals.

Antibody tests for identification of current and past infection with SARS-CoV-2

BACKGROUND

The diagnostic challenges associated with the COVID-19 pandemic resulted in rapid development of diagnostic test methods for detecting SARS-CoV-2 infection. Serology tests to detect the presence of antibodies to SARS-CoV-2 enable detection of past infection and may detect cases of SARS-CoV-2 infection that were missed by earlier diagnostic tests. Understanding the diagnostic accuracy of serology tests for SARS-CoV-2 infection may enable development of effective diagnostic and management pathways, inform public health management decisions and understanding of SARS-CoV-2 epidemiology.

OBJECTIVES

To assess the accuracy of antibody tests, firstly, to determine if a person presenting in the community, or in primary or secondary care has current SARS-CoV-2 infection according to time after onset of infection and, secondly, to determine if a person has previously been infected with SARS-CoV-2. Sources of heterogeneity investigated included: timing of test, test method, SARS-CoV-2 antigen used, test brand, and reference standard for non-SARS-CoV-2 cases.

SEARCH METHODS

The COVID-19 Open Access Project living evidence database from the University of Bern (which includes daily updates from PubMed and Embase and preprints from medRxiv and bioRxiv) was searched on 30 September 2020. We included additional publications from the Evidence for Policy and Practice Information and Co-ordinating Centre (EPPI-Centre) 'COVID-19: Living map of the evidence' and the Norwegian Institute of Public Health 'NIPH systematic and living map on COVID-19 evidence'. We did not apply language restrictions.

SELECTION CRITERIA

We included test accuracy studies of any design that evaluated commercially produced serology tests, targeting IgG, IgM, IgA alone, or in combination. Studies must have provided data for sensitivity, that could be allocated to a predefined time period after onset of symptoms, or after a positive RT-PCR test. Small studies with fewer than 25 SARS-CoV-2 infection cases were excluded. We included any reference standard to define the presence or absence of SARS-CoV-2 (including reverse transcription polymerase chain reaction tests (RT-PCR), clinical diagnostic criteria, and pre-pandemic samples).

DATA COLLECTION AND ANALYSIS

We use standard screening procedures with three reviewers. Quality assessment (using the QUADAS-2 tool) and numeric study results were extracted independently by two people. Other study characteristics were extracted by one reviewer and checked by a second. We present sensitivity and specificity with 95% confidence intervals (CIs) for each test and, for meta-analysis, we fitted univariate random-effects logistic regression models for sensitivity by eligible time period and for specificity by reference standard group. Heterogeneity was investigated by including indicator variables in the random-effects logistic regression models. We tabulated results by test manufacturer and summarised results for tests that were evaluated in 200 or more samples and that met a modification of UK Medicines and Healthcare products Regulatory Agency (MHRA) target performance criteria.

MAIN RESULTS

We included 178 separate studies (described in 177 study reports, with 45 as pre-prints) providing 527 test evaluations. The studies included 64,688 samples including 25,724 from people with confirmed SARS-CoV-2; most compared the accuracy of two or more assays (102/178, 57%). Participants with confirmed SARS-CoV-2 infection were most commonly hospital inpatients (78/178, 44%), and pre-pandemic samples were used by 45% (81/178) to estimate specificity. Over two-thirds of studies recruited participants based on known SARS-CoV-2 infection status (123/178, 69%). All studies were conducted prior to the introduction of SARS-CoV-2 vaccines and present data for naturally acquired antibody responses. Seventy-nine percent (141/178) of studies reported sensitivity by week after symptom onset and 66% (117/178) for convalescent phase infection. Studies evaluated enzyme-linked immunosorbent assays (ELISA) (165/527; 31%), chemiluminescent assays (CLIA) (167/527; 32%) or lateral flow assays (LFA) (188/527; 36%). Risk of bias was high because of participant selection (172, 97%); application and interpretation of the index test (35, 20%); weaknesses in the reference standard (38, 21%); and issues related to participant flow and timing (148, 82%). We judged that there were high concerns about the applicability of the evidence related to participants in 170 (96%) studies, and about the applicability of the reference standard in 162 (91%) studies. Average sensitivities for current SARS-CoV-2 infection increased by week after onset for all target antibodies. Average sensitivity for the combination of either IgG or IgM was 41.1% in week one (95% CI 38.1 to 44.2; 103 evaluations; 3881 samples, 1593 cases), 74.9% in week two (95% CI 72.4 to 77.3; 96 evaluations, 3948 samples, 2904 cases) and 88.0% by week three after onset of symptoms (95% CI 86.3 to 89.5; 103 evaluations, 2929 samples, 2571 cases). Average sensitivity during the convalescent phase of infection (up to a maximum of 100 days since onset of symptoms, where reported) was 89.8% for IgG (95% CI 88.5 to 90.9; 253 evaluations, 16,846 samples, 14,183 cases), 92.9% for IgG or IgM combined (95% CI 91.0 to 94.4; 108 evaluations, 3571 samples, 3206 cases) and 94.3% for total antibodies (95% CI 92.8 to 95.5; 58 evaluations, 7063 samples, 6652 cases). Average sensitivities for IgM alone followed a similar pattern but were of a lower test accuracy in every time slot. Average specificities were consistently high and precise, particularly for pre-pandemic samples which provide the least biased estimates of specificity (ranging from 98.6% for IgM to 99.8% for total antibodies). Subgroup analyses suggested small differences in sensitivity and specificity by test technology however heterogeneity in study results, timing of sample collection, and smaller sample numbers in some groups made comparisons difficult. For IgG, CLIAs were the most sensitive (convalescent-phase infection) and specific (pre-pandemic samples) compared to both ELISAs and LFAs (P < 0.001 for differences across test methods). The antigen(s) used (whether from the Spike-protein or nucleocapsid) appeared to have some effect on average sensitivity in the first weeks after onset but there was no clear evidence of an effect during convalescent-phase infection. Investigations of test performance by brand showed considerable variation in sensitivity between tests, and in results between studies evaluating the same test. For tests that were evaluated in 200 or more samples, the lower bound of the 95% CI for sensitivity was 90% or more for only a small number of tests (IgG, n = 5; IgG or IgM, n = 1; total antibodies, n = 4). More test brands met the MHRA minimum criteria for specificity of 98% or above (IgG, n = 16; IgG or IgM, n = 5; total antibodies, n = 7). Seven assays met the specified criteria for both sensitivity and specificity. In a low-prevalence (2%) setting, where antibody testing is used to diagnose COVID-19 in people with symptoms but who have had a negative PCR test, we would anticipate that 1 (1 to 2) case would be missed and 8 (5 to 15) would be falsely positive in 1000 people undergoing IgG or IgM testing in week three after onset of SARS-CoV-2 infection. In a seroprevalence survey, where prevalence of prior infection is 50%, we would anticipate that 51 (46 to 58) cases would be missed and 6 (5 to 7) would be falsely positive in 1000 people having IgG tests during the convalescent phase (21 to 100 days post-symptom onset or post-positive PCR) of SARS-CoV-2 infection.

AUTHORS' CONCLUSIONS

Some antibody tests could be a useful diagnostic tool for those in whom molecular- or antigen-based tests have failed to detect the SARS-CoV-2 virus, including in those with ongoing symptoms of acute infection (from week three onwards) or those presenting with post-acute sequelae of COVID-19. However, antibody tests have an increasing likelihood of detecting an immune response to infection as time since onset of infection progresses and have demonstrated adequate performance for detection of prior infection for sero-epidemiological purposes. The applicability of results for detection of vaccination-induced antibodies is uncertain.

Reactogenicity and immunogenicity of the second COVID-19 vaccination in patients with inborn errors of immunity or mannan-binding lectin deficiency

Background

Patients with inborn errors of immunity (IEI) are at increased risk for severe courses of SARS-CoV-2 infection. COVID-19 vaccination provides effective protection in healthy individuals. However, it remains unclear whether vaccination is efficient and safe in patients with constitutional dysfunctions of the immune system. Thus, we analyzed the humoral response, adverse reactions and assessed the disease activity of the underlying disease after COVID-19 vaccination in a cohort of patients suffering from IEIs or mannan-binding lectin deficiency (MBLdef).

Methods

Vaccination response was assessed after basic immunization using the Elecsys anti-SARS-CoV-2 S immunoassay and via Vero E6 cell based assay to detect neutralization capabilities. Phenotyping of lymphocytes was performed by flow cytometry. Patient charts were reviewed for disease activity, autoimmune phenomena as well as immunization status and reactogenicity of the vaccination. Activity of the underlying disease was assessed using a patient global numeric rating scale (NRS).

Results

Our cohort included 11 individuals with common variable immunodeficiency (CVID), one patient with warts hypogammaglobulinemia immunodeficiency myelokathexis (WHIM) syndrome, two patients with X-linked agammaglobulinemia (XLA), one patient with Muckle Wells syndrome, two patients with cryopyrin-associated periodic syndrome, one patient with Interferon-gamma (IFN-gamma) receptor defect, one patient with selective deficiency in pneumococcal antibody response combined with a low MBL level and seven patients with severe MBL deficiency. COVID-19 vaccination was generally well tolerated with little to no triggering of autoimmune phenomena. 20 out of 26 patients developed an adequate humoral vaccine response. 9 out of 11 patients developed a T cell response comparable to healthy control subjects. Tested immunoglobulin replacement therapy (IgRT) preparations contained Anti-SARS-CoV-2 S antibodies implicating additional protection through IgRT.

Summary

In summary the data support the efficacy and safety of a COVID-19 vaccination in patients with IEIs/MBLdef. We recommend evaluation of the humoral immune response and testing for virus neutralization after vaccination in this cohort.

Evaluation of the performance of multiple immunoassay diagnostic platforms on the National Microbiology Laboratory SARS-CoV-2 National Serology Panel

BACKGROUND

Serological assays designed to detect SARS-CoV-2 antibodies are being used in serological surveys and other specialized applications. As a result, and to ensure that the outcomes of serological testing meet high quality standards, evaluations are required to assess the performance of these assays and the proficiency of laboratories performing them.

METHODS

A panel of 60 plasma/serum samples from blood donors who had reverse transcriptase-polymerase chain reaction (RT-PCR) confirmed SARS-CoV-2 infections and 21 SARS-CoV-2 negative samples were secured and distributed to interested laboratories within Canada (n = 30) and the United States (n = 1). Participating laboratories were asked to provide details on the diagnostic assays used, the platforms the assays were performed on, and the results obtained for each panel sample. Laboratories were blinded with respect to the expected outcomes.

RESULTS

The performance of the different assays evaluated was excellent, with the high-throughput platforms of Roche, Ortho, and Siemens demonstrating 100% sensitivity. Most other high-throughput platforms had sensitivities of >93%, with the exception of the IgG assay using the Abbott ARCHITECT which had an average sensitivity of only 87%. The majority of the high-throughput platforms also demonstrated very good specificities (>97%).

CONCLUSION

This proficiency study demonstrates that most of the SARS-CoV-2 serological assays utilized by provincial public health or hospital laboratories in Canada have acceptable sensitivity and excellent specificity.

Humoral Response to the Third Dose of Sars-Cov-2 Vaccine in Kidney Transplant Recipients

BACKGROUND

Most solid organ transplant recipients did not develop an appreciable serologic response after 2 doses of the mRNA SARS-CoV-2 vaccine.

METHODS

We analyzed the humoral response after a third dose of the BNT162b2 vaccine in 130 kidney transplant recipients, compared to 48 health care workers, and associated factors, including prevaccine cellular immune response, by evaluating intracellular cytokine production after stimulation of donor's peripheral blood mononuclear cells.

RESULTS

After 2 doses, most of the controls (47 out of 48, 98%) and only 40% of kidney recipients (52 of 130) kidney recipients were seropositive (P < .001). Most seronegative recipients developed a serologic response after the booster (47 out 78, 60%), thus bringing the total number of seropositive recipients to 99 out of 130 (76%). After the third dose, there was a significant increase in antibodies titers in both groups. Decreased humoral response was significantly associated with an older age, lower lymphocyte count, and a lower level of antibodies before booster administration. CD4+TNFα+ and CD4+INFγ+ were correlated with mean increase in antibody titers.

CONCLUSIONS

A third dose of the BNT162b2 mRNA vaccine in kidney recipients is safe and effectively results in increased IgG anti-S levels, including in individuals who were seronegative after 2 doses. Long-term studies of the length of the immune response and protection are required.

Features of the humoral response to immunization "Gam-COVID-Vac" and in patients with COVID-19

The paper present the results of a survey of people who have undergone immunization with a combined vector vaccine for the prevention of coronavirus infection COVID-19 «Sputnik V - Gam-COVID-Vac», as well as COVID-19 recovalents. Using a quantitative enzyme-linked immunosorbent assay, the levels of specific IgG were determined in persons who had had different degrees of severity before vaccination, in persons who were immuno-negative before immunization, as well as in convalescents who had undergone coronavirus infection of varying severity. The immunological targeting of antibodies against various SARS-CoV-2 proteins is considered.

Performance of Severe Acute Respiratory Syndrome Coronavirus 2 Serological Diagnostic Tests and Antibody Kinetics in Coronavirus Disease 2019 Patients

Serological testing is recommended to support the detection of undiagnosed coronavirus disease 2019 (COVID-19) cases. However, the performance of serological assays has not been sufficiently evaluated. Hence, the performance of six severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) binding antibody assays [three chemiluminescence (CLIAs) and three lateral flow immunoassays (LFIAs)] and a surrogate virus neutralization test (sVNT) was analyzed in a total of 988 serum samples comprising 389 COVID-19-positives and 599 COVID-19-negatives. The overall diagnostic sensitivities of CLIAs and LFIAs ranged from 54.2 to 56.6% and from 56.3 to 64.3%, respectively. The overall diagnostic specificities of CLIAs and LFIAs ranged from 98.2 to 99.8% and from 97.3 to 99.0%, respectively. In the symptomatic group (n = 321), the positivity rate increased by over 80% in all assays > 14 days after symptom onset. In the asymptomatic group (n = 68), the positivity rate increased by over 80% in all assays > 21 days after initial RT-PCR detection. In LFIAs, negatively interpreted trace bands accounted for the changes in test performance. Most false-positive results were weak or trace reactions and showed negative results in additional sVNT. For six binding antibody assays, the overall agreement percentages ranged from 91.0 to 97.8%. The median inhibition activity of sVNT was significantly higher in the symptomatic group than in the asymptomatic group (50.0% vs. 29.2%; p < 0.0001). The median times to seropositivity in the symptomatic group were 9.7 days for CLIA-IgG, 9.2 and 9.8 days for two CLIAs-Total (IgM + IgG), 7.7 days for LFIA-IgM, 9.2 days for LFIA-IgG, and 8.8 days for sVNT-IgG, respectively. There was a strong positive correlation between the quantitative results of the four binding antibody assays and sVNT with Spearman ρ-values ranging from 0.746 to 0.854. In particular, when using LFIAs, we recommend using more objective interpretable assays or establishing a band interpretation system for each laboratory, accompanied by observer training. We also anticipate that sVNT will play an essential role in SARS-CoV-2 antibody testing and become the practical routine neutralizing antibody assay.

Seroprevalence of SARS-CoV-2 spike IgG antibodies after the second BNT162b2 mRNA vaccine in Japanese kidney transplant recipients

We aimed to evaluate the seroprevalence and investigated factors associated with seropositivity after the second SARS-CoV-2 mRNA vaccination in kidney transplant (KT) recipients. This retrospective study conducted between June and November 2021 included 106 KT recipients and 127 healthy controls who received the second dose of the BNT162b2 mRNA vaccine at least 7 days before the measurement of antibody titers. The antibody titer against the receptor-binding domain of SARS-CoV-2 spike (S) protein was determined. We compared seroprevalence rates (immunoglobulin G [IgG] level of ≥ 0.8 or ≥ 15 U/mL) between the healthy controls and KT recipients and identified factors associated with impaired humoral response. The seroprevalence rate of the healthy controls and KT recipients was 98% and 22%, respectively. Univariate logistic regression analysis revealed that age > 53 years, rituximab use, mycophenolate mofetil use, and KT vintage < 7 years were negatively associated with the rate of anti-SARS-CoV-2 S IgG ≥ 15 U/mL in KT recipients. ABO blood type incompatible KT was not significantly associated with seroprevalence. Humoral response after the second BNT162b2 mRNA vaccine was greatly hindered by immunosuppression therapy in KT recipients. Older age, rituximab use, mycophenolate mofetil use, and KT vintage may play key roles in seroconversion.

Effect of active anticancer therapy on serologic response to SARS-CoV-2 BNT162b2 vaccine in patients with urothelial and renal cell carcinoma

Objectives

To evaluate the serologic response to the BNT162b2 messenger ribonucleic acid vaccine in patients with urothelial carcinoma and renal cell carcinoma.

Methods

Between June 2021 and November 2021, we retrospectively evaluated blood samples from 60 healthy controls (control group), 57 patients with urothelial carcinoma, and 28 patients with renal cell carcinoma who had received two doses of the BNT162b2 vaccine at Hirosaki University Hospital. We determined the immunoglobulin G antibody titers against the severe acute respiratory syndrome coronavirus 2 spike receptor‐binding domain. Seropositivity was defined as ≥15 U/mL. We investigate factors associated with antibody titers and seropositivity in the patients with urothelial carcinoma and renal cell carcinoma.

Results

Antibody titers in the control, urothelial carcinoma, and renal cell carcinoma groups were 813, 431, and 500 U/mL, respectively. Seropositivity was 100%, 90%, and 96% in the control, urothelial carcinoma, and renal cell carcinoma groups, respectively. Of the 85 patients, 37 of 57 (65%) and 21 of 28 (75%) were actively undergoing anticancer treatment for urothelial carcinoma and renal cell carcinoma, respectively. Anti‐severe acute respiratory syndrome coronavirus 2 spike immunoglobulin G antibody titers and seropositivity was not significantly different between the patients with urothelial carcinoma and renal cell carcinoma. Anti‐severe acute respiratory syndrome coronavirus 2 spike immunoglobulin G antibody titers were not significantly associated with active anticancer therapy or steroid treatment for immune‐related adverse events. Univariable logistic regression analysis revealed that older age and metastatic disease were significantly and negatively associated with seropositivity.

Conclusions

Patients with urothelial carcinoma or renal cell carcinoma exhibited an adequate antibody response to the BNT162b2 vaccine. Active anticancer therapy was not significantly associated with seropositivity following vaccination with severe acute respiratory syndrome coronavirus 2 BNT162b2 in patients with urothelial carcinoma and renal cell carcinoma.

SARS-CoV-2 in inflammatory bowel disease population: Antibodies, disease and correlation with therapy

BACKGROUND

Guidelines recommend to cease inflammatory bowel disease (IBD) biologic therapy during coronavirus disease 2019 (COVID-19).

AIM

To investigate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody positivity in an IBD cohort, COVID-19 disease severity and to evaluate the correlation with clinical/therapeutic variables.

METHODS

Prospective observational cohort study. IBD patients were tested for SARS-CoV-2 IgG. Data on COVID-19 disease, demographics/therapeutics and clinical features of the IBD population were collected. IgG ≥ 7 was set for SARS-CoV-2 antibody positivity. Throat swab was performed in cases of IgG positivity. Correlations between antibody positivity or COVID-19 symptoms and therapeutic/clinical data were assessed.

RESULTS

In total, 103 IBD patients were enrolled. Among them, 18.4% had IgG ≥ 7. Multivariate analysis of antibody positivity correlated only with IBD treatment. For IgG ≥ 7, the odds ratio was 1.44 and 0.16 for azathioprine and mesalazine, respectively, vs biologic drugs (P = 0.0157 between them). COVID-19 related symptoms were reported in 63% of patients with IgG positivity. All but one patient with COVID-19 symptoms did not require ceasing IBD treatment or hospitalization. IBD treatment and body mass index correlated with COVID-19 disease development with symptoms.

CONCLUSION

The IBD population does not have a higher risk of severe COVID-19. The relative risk of having SARS-CoV-2 antibodies and symptoms was higher for patients taking azathioprine, then biologic therapy and lastly mesalazine. None of the patients under biologic therapy developed severe COVID-19.

SARS-CoV-2 in inflammatory bowel disease population: Antibodies, disease and correlation with therapy

BACKGROUND

Guidelines recommend to cease inflammatory bowel disease (IBD) biologic therapy during coronavirus disease 2019 (COVID-19).

AIM

To investigate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody positivity in an IBD cohort, COVID-19 disease severity and to evaluate the correlation with clinical/therapeutic variables.

METHODS

Prospective observational cohort study. IBD patients were tested for SARS-CoV-2 IgG. Data on COVID-19 disease, demographics/therapeutics and clinical features of the IBD population were collected. IgG ≥ 7 was set for SARS-CoV-2 antibody positivity. Throat swab was performed in cases of IgG positivity. Correlations between antibody positivity or COVID-19 symptoms and therapeutic/clinical data were assessed.

RESULTS

In total, 103 IBD patients were enrolled. Among them, 18.4% had IgG ≥ 7. Multivariate analysis of antibody positivity correlated only with IBD treatment. For IgG ≥ 7, the odds ratio was 1.44 and 0.16 for azathioprine and mesalazine, respectively, vs biologic drugs (P = 0.0157 between them). COVID-19 related symptoms were reported in 63% of patients with IgG positivity. All but one patient with COVID-19 symptoms did not require ceasing IBD treatment or hospitalization. IBD treatment and body mass index correlated with COVID-19 disease development with symptoms.

CONCLUSION

The IBD population does not have a higher risk of severe COVID-19. The relative risk of having SARS-CoV-2 antibodies and symptoms was higher for patients taking azathioprine, then biologic therapy and lastly mesalazine. None of the patients under biologic therapy developed severe COVID-19.

A Novel Quantitative Multi-Component Serological Assay for SARS-CoV-2 Vaccine Evaluation

A multi-component microarray, applying a novel analysis algorithm, was developed for quantitative evaluation of the SARS-CoV-2 vaccines' immunogenicity. The array enables simultaneous quantitation of IgG, IgM, and IgA, specific to the SARS-CoV-2 spike, receptor binding domain, and nucleocapsid proteins. The developed methodology is based on calculating an apparent immunoglobulin signal from the linear range of the fluorescent read-outs generated by scanning the microarray slides at different exposure times. A dedicated algorithm, employing a rigorous set of embedded conditions, then generates a normalized signal for each of the unique assays. Qualification of the multi-component array performance (evaluating linearity, extended dynamic-range, specificity, precision, and accuracy) was carried out with an in-house COVID-19, qRT-PCR positive serum, as well as pre-pandemic commercial negative sera. Results were compared to the WHO international standard for anti-SARS-CoV-2 immunoglobulins. Specific IgG, IgM, and IgA signals obtained by this array enabled successful discrimination between SARS-CoV-2 q-RT-PCR positive (seroconverted SARS-CoV-2 patients) and negative (naïve) samples. This array is currently used for evaluation of the humoral response to BriLife, the VSV-based Israeli vaccine during phase I/II clinical trials.

Systemic Adverse Effects Induced by the BNT162b2 Vaccine Are Associated with Higher Antibody Titers from 3 to 6 Months after Vaccination

Objective: We aimed to determine the relationship between vaccine-related adverse effects and antibody (Ab) titers from 3 to 6 months after the second dose of the BNT162b2 coronavirus disease 2019 (COVID-19) mRNA vaccine (Pfizer/BioNTech) in Japan. Methods: We enrolled 378 healthcare workers (255 women and 123 men) whose Ab titers were analyzed 3 and 6 months after the second dose in our previous study and whose characteristics and adverse effects were collected previously by using a structured self-report questionnaire. Results: The workers’ median age was 44 years. Although injection-site symptoms occurred with almost equal frequency between the first and second doses, systemic adverse effects, such as general fatigue and fever, were significantly more frequent after the second dose than after the first dose. Multivariate analysis showed that fever was significantly correlated with female participants for the second dose (odds ratio (OR), 2.139; 95% confidence interval (95% CI), 1.185–3.859), older age for the first dose (OR, 0.962; 95% CI, 0.931–0.994) and second dose (OR, 0.957; 95% CI, 0.936–0.979), and dyslipidemia for the first dose (OR, 8.750; 95% CI, 1.814–42.20). Age-adjusted Ab titers at 3 months after vaccination were 23.7% and 23.4% higher in patients with a fever than in those without a fever after the first and second dose, respectively. In addition, age-adjusted Ab titers at 3 and 6 months after the second dose were, respectively, 21.7% and 19.3% higher in the group in which an anti-inflammatory agent was used than in the group without the use of an anti-inflammatory agent. Conclusion: Participants with systemic adverse effects tend to have higher Ab titers from 3 to 6 months after the second dose of the BNT162b2 vaccine. Our results may encourage vaccination, even among people with vaccine hesitancy related to relatively common systemic adverse effects.

B Cell Depletion and SARS-CoV-2 Vaccine Responses in Neuroimmunologic Patients

OBJECTIVE

The study was undertaken to assess the impact of B cell depletion on humoral and cellular immune responses to severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) vaccination in patients with various neuroimmunologic disorders on anti-CD20 therapy. This included an analysis of the T cell vaccine response to the SARS-CoV-2 Delta variant.

METHODS

We investigated prospectively humoral and cellular responses to SARS-CoV-2 mRNA vaccination in 82 patients with neuroimmunologic disorders on anti-CD20 therapy and 82 age- and sex-matched healthy controls. For quantification of antibodies, the Elecsys anti-SARS-CoV-2 viral spike (S) immunoassay against the receptor-binding domain (RBD) was used. IFN-gamma enzyme-linked immunosorbent spot assays were performed to assess T cell responses against the SARS-CoV-2 Wuhan strain and the Delta variant.

RESULTS

SARS-CoV-2-specific antibodies were found less frequently in patients (70% [57/82]) compared with controls (82/82 [100%], p < 0.001). In patients without detectable B cells (<1 B cell/mcl), seroconversion rates and antibody levels were lower compared to nondepleted (≥1 B cell/mcl) patients (p < 0.001). B cell levels ≥1 cell/mcl were sufficient to induce seroconversion in our cohort of anti-CD20 treated patients. In contrast to the antibody response, the T-cell response against the Wuhan strain and the Delta variant was more pronounced in frequency (p < 0.05) and magnitude (p < 0.01) in B-cell depleted compared to nondepleted patients.

INTERPRETATION

Antibody responses to SARS-CoV-2 mRNA vaccinnation can be attained in patients on anti-CD20 therapy by the onset of B cell repopulation. In the absence of B cells, a strong T cell response is generated which may help to protect against severe coronavirus disease 2019 (COVID-19) in this high-risk population. ANN NEUROL 2022;91:342-352.

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.

Healthcare Workers in South Korea Maintain a SARS-CoV-2 Antibody Response Six Months After Receiving a Second Dose of the BNT162b2 mRNA Vaccine

Background

Effective vaccines against coronavirus disease 2019 (COVID-19) are available worldwide; however, the longevity of vaccine effectiveness is not known.

Objective

We performed a prospective observational study to assess the antibody response of healthcare workers against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) after BNT162b2 mRNA COVID-19 vaccination.

Methods

SARS-CoV-2 neutralizing antibody (nAb) and spike (S) protein-IgG (S-IgG) antibody titers were examined in participants who received two doses of the BNT162b2 mRNA COVID-19 vaccine in a single center between March 1, 2021, and October 11, 2021. Antibody levels were analyzed at four times: before vaccination (visit 1), 4 weeks after the first vaccination (visit 2), 3 months after the second vaccination (visit 3), and 6 months after the second vaccination (visit 4).

Results

A total of 249 healthcare workers at Jeju National University Hospital were enrolled in this study, and 982 blood samples were analyzed. The mean age was 38.1 ± 9.5 years, and 145 (58.2%) participants were females. Positive nAbs (inhibition rates ≥ 20%) were measured in 166/249 (66.7%) subjects at visit 2, 237/243 (97.5%) subjects at visit 3, and 150/237 (63.3%) subjects at visit 4. A S-IgG (≥50 AU/mL) positivity was detected in 246/249 (98.8%) subjects at visit 1, and all participants had positive S-IgG antibody levels at visits 3 and 4 after being fully vaccinated. Further analysis of S-IgG levels revealed a median quantitative antibody level of 1275.1 AU/mL (interquartile range [IQR] 755.5–2119.0) at visit 2, 2765.9 AU/mL (IQR 1809.8–4138.4) at visit 3, and 970.1 AU/mL (IQR 606.0–1495.9) at visit 4. Patient characteristics, such as age, body mass index, and comorbidity, had no relationship with nAb or S-IgG levels at any of the visits. Considering the change in antibody levels over time, both nAb and S-IgG levels at visit 4 decreased compared with the corresponding levels at visit 3. No evidence of SARS-CoV-2 infection was found among any of the participants throughout the study.

Conclusions

The BNT162b2 mRNA vaccine was effective in protecting healthcare personnel working in COVID-19-related departments. While the level of S-IgG antibodies was maintained for 6 months after the second vaccination, nAb levels waned over this 6-month period, indicating the need for a booster vaccination in some healthcare workers 6 months after full vaccination. Herein, we suggest that further studies are needed to evaluate the need for an interval of booster vaccination after full vaccination.

Head-To-Head Comparison of Response Rates to the Two mRNA SARS-CοV-2 Vaccines in a Large Cohort of Solid Organ Transplant (SOT) Recipients

Due to their higher risk of developing life-threatening COVID-19 disease, solid organ transplant (SOT) recipients have been prioritized in the vaccination programs of many countries. However, there is increasing evidence of reduced immunogenicity to SARS-CοV-2 vaccination. The present study investigated humoral response, safety, and effectiveness after the two mRNA vaccines in 455 SOT recipients. Overall, the antibody response rate was low, at 39.6%. Higher immunogenicity was detected among individuals vaccinated with the mRNA1273 compared to those with the BNT162b2 vaccine (47% vs. 36%, respectively, p = 0.025) as well as higher median antibody levels of 31 (7, 372) (AU/mL) vs. 11 (7, 215) AU/mL, respectively. Among the covariates assessed, vaccination with the BNT162b2 vaccine, antimetabolite- and steroid-containing immunosuppression, female gender, the type of transplanted organ and older age were factors that negatively influenced immune response. Only mild adverse effects were observed. Our findings confirm poor immunogenicity after vaccination, implicating a reevaluation of vaccination policy in SOT recipients.

Rapid Weight Loss, Central Obesity Improvement and Blood Glucose Reduction Are Associated with a Stronger Adaptive Immune Response Following COVID-19 mRNA Vaccine

Obesity is associated with a poor COVID-19 prognosis, and it seems associated with reduced humoral response to vaccination. Public health campaigns have advocated for weight loss in subjects with obesity, hoping to eliminate this risk. However, no evidence proves that weight loss leads to a better prognosis or a stronger immune response to vaccination. We aimed to investigate the impact of rapid weight loss on the adaptive immune response in subjects with morbid obesity. Twenty-one patients followed a hypocaloric, very-low-carbohydrate diet one week before to one week after the two mRNA vaccine doses. The diet’s safety and efficacy were assessed, and the adaptive humoral (anti-SARS CoV-2 S antibodies, Abs) and cell-mediated responses (IFNγ secretion on stimulation with two different SARS CoV-2 peptide mixes, IFNγ-1 and IFNγ-2) were evaluated. The patients lost ~10% of their body weight with metabolic improvement. A high baseline BMI correlated with a poor immune response (R −0.558, p = 0.013 for IFNγ-1; R −0.581, p = 0.009 for IFNγ-2; R −0.512, p = 0.018 for Abs). Furthermore, there was a correlation between weight loss and higher IFNγ-2 (R 0.471, p = 0.042), and between blood glucose reduction and higher IFNγ-1 (R 0.534, p = 0.019), maintained after weight loss and waist circumference reduction adjustment. Urate reduction correlated with higher Abs (R 0.552, p = 0.033). In conclusion, obesity is associated with a reduced adaptive response to a COVID-19 mRNA vaccine, and weight loss and metabolic improvement may reverse the effect.

Humoral and cellular immune response to severe acute respiratory syndrome coronavirus-2 vaccination in haemodialysis and kidney transplant patients

End-stage renal disease (ESRD) patients are amongst the vulnerable groups and thus prioritized in the Coronavirus disease-2019 vaccination programmes. However, this cohort was excluded from vaccine-trials and yet shares the same vaccination scheme with the general population. Here, we explore trends of immune response-proportions amongst ESRD patients on renal replacement therapy for up to 4 weeks post-vaccination completion with Pfizer/Moderna vaccines. From inception to 10 July 2021, we searched six online-databases for articles reporting humoral and cellular immune response proportions for up to 4 weeks post booster-vaccination. We pooled the responders' proportions by meta-analysis and conducted a meta-regression stratifying outcomes by significant confounders. Twenty-seven eligible studies reported 2789 ESRD patients. 1337, 1452 and 477 were on haemodialysis, received kidney transplantation, and healthy controls, respectively. Haemodialysis patients' proportions of humoral and cellular immune responses varied from 87.29% (80.77-93.81)-88.78% (86.76-90.80) and 62.86% (56.56, 69.17)-85.78% (78.99, 92.57), respectively, between first- and fourth-weeks. Kidney transplant patients' proportions of humoral and cellular immune responses ranged from 2.6% (0.06-13.48)-29.87% (27.68, 32.07) and 5.13% (0.63-17.3)-59.84% (54.57-65.10), respectively, between first- and fourth-weeks. All healthy controls maintained ≥93% proportions of both responses throughout the follow-up. Study design and country of study influenced the pooled response proportions. Conclusively, haemodialysis and kidney transplant patients have lower proportions of humoral and cellular immune responses than healthy controls. However, haemodialysis patients' response proportions improve, reaching near healthy-control levels by the fourth week. Kidney transplant patients' lower responses' proportions also improve but remain significantly lower than healthy controls throughout four-weeks. The "one-size-fits-all" vaccination scheme might be inadequate for kidney transplant patients.

Central obesity, smoking habit, and hypertension are associated with lower antibody titres in response to COVID-19 mRNA vaccine

AIMS

To explore variables associated with the serological response following COVID-19 mRNA vaccine.

METHODS

Eighty-six healthcare workers adhering to the vaccination campaign against COVID-19 were enrolled in January-February 2021. All subjects underwent two COVID-19 mRNA vaccine inoculations (Pfizer/BioNTech) separated by 3 weeks. Blood samples were collected before the 1st and 1-4 weeks after the second inoculation. Clinical history, demographics, and vaccine side effects were recorded. Baseline anthropometric parameters were measured, and body composition was performed through dual-energy-X-ray absorptiometry.

RESULTS

Higher waist circumference was associated with lower antibody (Ab) titres (R = -0.324, p = 0.004); smokers had lower levels compared to non-smokers [1099 (1350) vs. 1921 (1375), p = 0.007], as well as hypertensive versus normotensive [650 ± 1192 vs. 1911 (1364), p = 0.001] and dyslipideamic compared to those with normal serum lipids [534 (972) vs 1872 (1406), p = 0.005]. Multivariate analysis showed that higher waist circumference, smoking, hypertension, and longer time elapsed since second vaccine inoculation were associated with lower Ab titres, independent of BMI, age. and gender.

CONCLUSIONS

Central obesity, hypertension, and smoking are associated with lower Ab titres following COVID-19 vaccination. Although it is currently impossible to determine whether lower SARS-CoV-2 Abs lead to higher likelihood of developing COVID-19, it is well-established that neutralizing antibodies correlate with protection against several viruses including SARS-CoV-2. Our findings, therefore, call for a vigilant approach, as subjects with central obesity, hypertension, and smoking could benefit from earlier vaccine boosters or different vaccine schedules.

Attenuation of Antibody Titers from 3 to 6 Months after the Second Dose of the BNT162b2 Vaccine Depends on Sex, with Age and Smoking Risk Factors for Lower Antibody Titers at 6 Months

Objective: We aimed to determine antibody titers at six months and their percentage change from three to six months after the second dose of the BNT162b2 coronavirus disease 2019 (COVID-19) mRNA vaccine (Pfizer/BioNTech) and to explore clinical variables associated with titers in Japan. Methods: We enrolled 365 healthcare workers (250 women, 115 men) whose three-month antibody titers were analyzed in our previous study and whose blood samples were collected 183 ± 15 days after the second dose. Participant characteristics, collected previously, were used. The relationships of these factors with antibody titers at six months and percentage changes in antibody titers from three to six months were analyzed. Results: Median age was 44 years. Median antibody titer at six months was 539 U/mL. Older participants had significantly lower antibody titers (20s, 752 U/mL; 60s–70s, 365 U/mL). In age-adjusted analysis, smoking was the only factor associated with lower antibody titers. Median percentage change in antibody titers from three to six months was −29.4%. The only factor significantly associated with the percentage change in Ab titers was not age or smoking, but sex (women, −31.6%; men, −25.1%). Conclusion: The most important factors associated with lower antibody titers at six months were age and smoking, as at three months, probably reflecting their effect on peak antibody titers. However, the only factor significantly associated with the attenuation in Ab titers from three to six months was sex, which reduced the sex difference seen during the first three months. Antibody titers may be affected by different factors at different time points.

Quantitative serological evaluation as a valuable tool in the COVID-19 vaccination campaign

OBJECTIVES

After exceptional research efforts, several vaccines were developed against SARS-CoV-2 which sustains the pandemic COVID-19. The Comirnaty vaccine showed high efficacy in clinical trials and was the first to be approved for its distribution to the general population. We evaluated the immune response induced by the first vaccine dose in different sex/age groups and subjects with or without naturally present anti-SARS-CoV-2 antibodies.

METHODS

As part of an Italian multicenter project (Covidiagnostix), serum samples from 4,290 health-professionals were serologically tested the day of the first vaccination dose, and 21 days later, using two different instrumentations (Siemens-Healthineers and Roche).

RESULTS

In total, 97% of samples showed the presence of specific antibodies 21 days after the vaccination dose; the percentage of non-responders increased with age in both genders. Remarkably, naturally seropositive individuals showed antibody persistence up to 11 months and an exceptionally higher vaccination response compared to subjects never infected by SARS-CoV-2.

CONCLUSIONS

This study highlighted the importance of the serological test i) to identify naturally SARS-CoV-2 seropositive individuals and ii) to evaluate the antibody level elicited by the first vaccination dose. Both tests, highlighted differences in the immune response, when subjects were stratified by sex and age, and between naturally seropositive and seronegative subjects. The data obtained show how serological tests could play a crucial role in the triage of the population subjected to the vaccination campaign for COVID-19. The definition of suitable instrumentation-specific thresholds is needed to correctly follow eventually acquired post-vaccination immunity in the general population.

Antibody Titer Kinetics and SARS-CoV-2 Infections Six Months after Administration with the BNT162b2 Vaccine

Background: Studies reporting the long-term humoral response after receiving the BNT162b2 COVID-19 vaccine are important to drive future vaccination strategies. Yet, available literature is scarce. Covidiagnostix is a multicenter study designed to assess the antibody response in >1000 healthcare professionals (HCPs) who received the BNT162b2 vaccine. Methods: Serum was tested at time-0 (T₀), before the first dose, T₁, T_2, and T₃, respectively, 21, 42, and 180 days after T₀. Antibodies against the SARS-CoV-2 nucleocapsid-protein were measured to assess SARS-CoV-2 infections, whereas antibodies against the receptor-binding domain of the spike protein were measured to assess the vaccine response. Neutralization activity against the D614G, B.1.1.7, and B.1.351 variants were also analyzed. Results: Six months post-vaccination HCPs showed an antibody titer decrease of approximately 70%, yet, the titer was still one order of magnitude higher than that of seropositive individuals before vaccination. We identified 12 post-vaccination infected HCPs. None showed severe symptoms. Interestingly, most of them showed titers at T₂ above the neutralization thresholds obtained from the neutralization activity experiments. Conclusion: Vaccination induces a humoral response which is well detectable even six months post-vaccination. Vaccination prevents severe COVID-19 cases, yet post-vaccination infection is possible even in the presence of a high anti-S serum antibody titer.

Investigating Adherence to COVID-19 Vaccination and Serum Antibody Concentration among Hospital Workers-The Experience of an Italian Private Hospital

SARS-CoV-2 transmission has been high, especially among healthcare workers worldwide during the first wave. Vaccination is recognized as the most effective approach to combat the pandemic, but hesitation to get vaccinated represents an obstacle. Another important issue is the duration of protection after administration of the full vaccination cycle. Based on these premises, we conducted a study to evaluate vaccination adherence and the anti-S antibodies levels among hospital workers, from January to March, 2021. To assess adherence, an anonymous questionnaire was used. Anti-S antibody levels were obtained from the monitoring serological sample database. In total, 56.2% of the unvaccinated people did not report a previous infection from COVID-19. Among those who have not been vaccinated, 12.5% showed distrust against the vaccine, 8.3% stated to have received contraindications to the vaccination, and 6.3% did not report any choice. Analyzing anti-S antibody levels, only one person was found to have a value below the lower cut-off, two weeks, and three months after receiving their second dose. One was below the cut-off after two weeks, and then above the same cut-off after three months. The results of our survey should be seen as a stimulus to further sensitize hospital staff to the importance of vaccination and pay attention to anti-S antibody levels monitoring.

Serum antibody response to BNT162b2 after natural SARS-CoV-2 infection

BACKGROUND

There is preliminary evidence that individuals with previous SARS-CoV-2 infections exhibit a more pronounced antibody response. However, these assumptions have not yet been supported by data obtained through various CE-marked tests. This study aimed to close this gap.

METHODS

Sixty-nine seronegatives and 12 individuals post-SARS-CoV-2 infection (tested by CE-labelled Roche NC immunoassay or PCR-confirmed assay) were included 21 ± 1 days after receiving the first dose of the Pfizer/BioNTech BNT162b2 vaccine. Antibody response to viral spike protein (S) was assessed by CE-labelled Roche S and DiaSorin S1/S2 assays and by a surrogate virus neutralization test (sVNT).

RESULTS

After a single dose of BNT162b2, individuals after natural SARS-CoV-2 infection presented with markedly higher anti-S levels than naïve individuals (Roche S: 9078.5 BAU/mL [5267.0-24 298.5] vs 79.6 [24.7-142.3]; and DiaSorin S1/S2: 1465.0 AU/mL [631.0-5365.0] vs 63.7 [47.8-87.5]) and showed all the maximum observed inhibition activity in the sVNT (98%), without overlaps between groups. There was a trend for higher responses in those with a more distant infection, although not statistically significant. The relative antibody increase after dose 2 was significantly higher among naïve individuals (25-fold), but antibody levels remained below that of seropositives.

CONCLUSIONS

Compared with naïve individuals, seropositives after natural SARS-CoV-2 infection presented with a substantially higher antibody response already after dose 1 of BNT162b2, as measured by two CE-marked in vitro diagnostic tests and a sVNT. These results should stimulate discussion and research on whether individuals after previous SARS-CoV-2 infection would benefit from a two-part vaccination schedule or whether these currently much-needed second doses could be saved.

SARS-CoV-2 vaccination in rituximab-treated patients: B cells promote humoral immune responses in the presence of T-cell-mediated immunity

OBJECTIVES

Evidence suggests that B cell-depleting therapy with rituximab (RTX) affects humoral immune response after vaccination. It remains unclear whether RTX-treated patients can develop a humoral and T-cell-mediated immune response against SARS-CoV-2 after immunisation.

METHODS

Patients under RTX treatment (n=74) were vaccinated twice with either mRNA-1273 or BNT162b2. Antibodies were quantified using the Elecsys Anti-SARS-CoV-2 S immunoassay against the receptor-binding domain (RBD) of the spike protein and neutralisation tests. SARS-CoV-2-specific T-cell responses were quantified by IFN-γ enzyme-linked immunosorbent spot assays. Prepandemic healthy individuals (n=5), as well as healthy individuals (n=10) vaccinated with BNT162b2, served as controls.

RESULTS

All healthy controls developed antibodies against the SARS-CoV-2 RBD of the spike protein, but only 39% of the patients under RTX treatment seroconverted. Antibodies against SARS-CoV-2 RBD significantly correlated with neutralising antibodies (τ=0.74, p<0.001). Patients without detectable CD19+ peripheral B cells (n=36) did not develop specific antibodies, except for one patient. Circulating B cells correlated with the levels of antibodies (τ=0.4, p<0.001). However, even patients with a low number of B cells (<1%) mounted detectable SARS-CoV-2-specific antibody responses. SARS-CoV-2-specific T cells were detected in 58% of the patients, independent of a humoral immune response.

CONCLUSIONS

The data suggest that vaccination can induce SARS-CoV-2-specific antibodies in RTX-treated patients, once peripheral B cells at least partially repopulate. Moreover, SARS-CoV-2-specific T cells that evolved in more than half of the vaccinated patients may exert protective effects independent of humoral immune responses.

Age and Smoking Predict Antibody Titres at 3 Months after the Second Dose of the BNT162b2 COVID-19 Vaccine

Objective: We aimed to determine antibody (Ab) titres 3 months after the second dose of the BNT162b2 coronavirus disease-2019 (COVID-19) vaccine and to explore clinical variables predicting these titres in Japan. Methods: We enrolled 378 healthcare workers (255 women, 123 men) whose blood samples were collected 91 ± 15 days after the second of two inoculations of the BNT162b2 COVID-19 mRNA vaccine (Pfizer/BioNTech) given 3 weeks apart. Medical histories and demographic characteristics were recorded using a structured self-reported questionnaire. The relationships between Ab titres and these factors were analysed. Results: Median age (interquartile range (IQR)) of the participants was 44 (32–54) years. Median Ab titre (IQR) against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike antigen was 764 (423–1140) U/mL. Older participants had significantly lower Ab titres; median (IQR) Ab titres were 942 (675–1390) and 1095 (741–1613) U/mL in men and women in their 20s, respectively, but 490 (297–571) and 519 (285–761) U/mL in men and women in their 60–70s, respectively. In the age-adjusted analysis, the only risk factors for lower Ab titres were male sex and smoking. However, the sex difference may have arisen from the sex difference in smoking rate. Moreover, Ab titres were significantly lower in current smokers than in ex-smokers. Conclusions: The most important factors associated with low Ab titres were age and smoking habit. In particular, current smoking status caused lower Ab titres, and smoking cessation before vaccination may improve the individual efficacy of the BNT162b2 vaccine.

Kidney transplant recipients vaccinated before transplantation maintain superior humoral response to SARS-CoV-2 vaccine

Majority of transplant recipients did not develop an appreciable humoral response following SARS-CoV-2 vaccine, in contrast to dialysis patients and healthy individuals. We analyzed the serologic response to BNT162b2 (Pfizer-BioNTech) vaccine in a cohort of 19 kidney transplant recipients, vaccinated prior to transplantation, compare to 109 recipients vaccinated after transplantation, and to 39 healthcare workers, by determining the level of anti-spike antibodies after transplantation. All controls and 17 of 19 (90%) of recipients vaccinated before transplant were seropositive, while only 49 of 109 (45%) recipients vaccinated post-transplant had positive serology (P < .001). Median anti-spike IgG in the group of kidney transplant recipients vaccinated after transplantation (10.7 AU/ml, [IQR 0-62.5]) was lower than the patients vaccinated before transplantation (66.2 AU/ml [21.6-138]), which was significantly lower than in the controls (156 AU/ml [99.7-215.5]). Negative humoral response was associated with vaccination post transplantation (odds ratio 22.4), older age (OR = 1.04), and longer time on dialysis (OR = 1.02), while higher lymphocyte count at time of vaccination was protective (OR = .52). Our findings of sustained superior humoral response to SARS-CoV-2 vaccine in kidney transplant recipients vaccinated prior to transplantation strongly support the recommendations of SARS-CoV-2 vaccination of transplant candidates, especially those younger than 60 years.

Anti-Spike Protein Assays to Determine SARS-CoV-2 Antibody Levels: a Head-to-Head Comparison of Five Quantitative Assays

Reliable quantification of the antibody response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is highly relevant, e.g., for identifying possible vaccine failure and estimating the time of protection. Therefore, we evaluated five different anti-SARS-CoV-2 antibody assays regarding the quantification of anti-spike (S) antibodies. Sera from 69 SARS-CoV-2-naive individuals 21 ± 1 days after vaccination with a single dose of BNT162b2 (Pfizer/BioNTech) were tested using the following quantitative assays: Roche S total antibody, DiaSorin trimeric spike IgG, DiaSorin S1/S2 IgG, Abbott II IgG, and Serion/Virion IgG. Results were further compared to the percent inhibition calculated from a surrogate virus neutralization test (sVNT). Individual values were distributed over several orders of magnitude for all assays. Although the assays were in good overall agreement (ρ = 0.80 to 0.94), Passing-Bablok regression revealed systematic constant and proportional differences, which could not be eliminated by converting the results to binding antibody units (BAU) per milliliter, as suggested by the manufacturers. Seven (10%) individuals had negative sVNT results (i.e., <30% inhibition). These samples were identified by most assays and yielded significantly lower binding antibody levels. Although all assays showed good correlation, they were not interchangeable, even when converted to BAU per milliliter using the WHO international standard for SARS-CoV-2 immunoglobulin. This highlights the need for further standardization of SARS-CoV-2 serology. IMPORTANCE Reliable quantification of the antibody response to SARS-CoV-2 is highly relevant, e.g., for identifying possible vaccine failure and estimating the time of protection. We compared the performance of five CE marked tests that quantify antibodies against the viral spike protein. Our findings suggest that, although all assays showed good correlation, their results were not interchangeable, even when converted to BAU per milliliter using the WHO international standard for SARS-CoV-2 immunoglobulin. This highlights the need for further standardization of SARS-CoV-2 serology.

Probability-Based Estimates of Severe Acute Respiratory Syndrome Coronavirus 2 Seroprevalence and Detection Fraction, Utah, USA

We aimed to generate an unbiased estimate of the incidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in 4 urban counties in Utah, USA. We used a multistage sampling design to randomly select community-representative participants >12 years of age. During May 4–June 30, 2020, we collected serum samples and survey responses from 8,108 persons belonging to 5,125 households. We used a qualitative chemiluminescent microparticle immunoassay to detect SARS-CoV-2 IgG in serum samples. We estimated the overall seroprevalence to be 0.8%. The estimated seroprevalence-to-case count ratio was 2.5, corresponding to a detection fraction of 40%. Only 0.2% of participants from whom we collected nasopharyngeal swab samples had SARS-CoV-2–positive reverse transcription PCR results. SARS-CoV-2 antibody prevalence during the study was low, and prevalence of PCR-positive cases was even lower. The comparatively high SARS-CoV-2 detection rate (40%) demonstrates the effectiveness of Utah’s testing strategy and public health response.

Large-scale study of antibody titer decay following BNT162b2 mRNA vaccine or SARS-CoV-2 infection

BACKGROUND

Immune protection following either vaccination or infection with SARS-CoV-2 decreases over time.

OBJECTIVE

To determine the kinetics of SARS-CoV-2 IgG antibodies following administration of two doses of BNT162b2 vaccine, or SARS-CoV-2 infection in unvaccinated individuals.

METHODS

Antibody titers were measured between January 31, 2021, and July 31, 2021 in two mutually exclusive groups: i) vaccinated individuals who received two doses of BNT162b2 vaccine and had no history of previous infection with COVID-19 and ii) SARS-CoV-2 convalescents who had not received the vaccine.

RESULTS

A total of 2,653 individuals fully vaccinated by two doses of vaccine during the study period and 4,361 convalescent patients were included. Higher SARS-CoV-2 IgG antibody titers were observed in vaccinated individuals (median 1581 AU/mL IQR [533.8-5644.6]) after the second vaccination, than in convalescent individuals (median 355.3 AU/mL IQR [141.2-998.7]; p<0.001). In vaccinated subjects, antibody titers decreased by up to 40% each subsequent month while in convalescents they decreased by less than 5% per month. Six months after BNT162b2 vaccination 16.1% subjects had antibody levels below the seropositivity threshold of <50 AU/mL, while only 10.8% of convalescent patients were below <50 AU/mL threshold after 9 months from SARS-CoV-2 infection.

CONCLUSIONS

This study demonstrates individuals who received the Pfizer-BioNTech mRNA vaccine have different kinetics of antibody levels compared to patients who had been infected with the SARS-CoV-2 virus, with higher initial levels but a much faster exponential decrease in the first group.

FUNDING

This research was internally funded by Leumit Health Services (LHS) and was supported in part by the Intramural Research Program, National Institutes of Health, National Cancer Institute, Center for Cancer Research.The content of this publication does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.

IMPACT STATEMENT

Large scale study display the kinetics of SARS-CoV-2 IgG antibodies present in individuals vaccinated with two doses of mRNA vaccine vs. unvaccinated patients who had recovered from the disease: initial levels of antibody are much higher in vaccinated patients, but decrease faster.

Assessing the Quality of Serological Testing in the COVID-19 Pandemic: Results of a European External Quality Assessment (EQA) Scheme for Anti-SARS-CoV-2 Antibody Detection

External quality assessment (EQA) is a key instrument for achieving harmonization, and thus a high quality, of diagnostic procedures. As reliable test results are crucial for accurate assessment of SARS-CoV-2 infection prevalence, vaccine response, and immunity, and thus for successful management of the ongoing COVID-19 pandemic, the Reference Institute for Bioanalytics (RfB) was the first EQA provider to offer an open scheme for anti-SARS-CoV-2 antibody detection. The main objectives of this EQA were (i) to gain insights into the current diagnostic landscape and the performance of serological tests in Europe and (ii) to provide recommendations for diagnostic improvements. Within the EQA, a blinded panel of precharacterized human serum samples with variable anti-SARS-CoV-2 antibody titers was provided for detection of anti-SARS-CoV-2 IgG, IgA, and IgM antibodies. Across the three distribution rounds in 2020, 284 laboratories from 22 countries reported a total of 3,744 results for anti-SARS-CoV-2 antibody detection using more than 24 different assays for IgG. Overall, 97/3,004 results were false for anti-SARS-CoV-2 IgG, 88/248 for IgA, and 34/124 for IgM. Regarding diagnostic sensitivity and specificity, substantial differences were found between the different assays used, as well as between certified and noncertified tests. For cutoff samples, a drop in the diagnostic sensitivity to 46.3% and high interlaboratory variability were observed. In general, this EQA highlights the current variability of anti-SARS-CoV-2 antibody detection, technical limitations with respect to cutoff samples, and the lack of harmonization of testing procedures. Recommendations are provided to help laboratories and manufacturers further improve the quality of anti-SARS-CoV-2 serological diagnostics.

Clinical performance of the Elecsys® anti-SARS-CoV-2 combined in an algorithm with two specific anti-IgG immunoassays for the evaluation of the serological response of patients with COVID-19 in a population with a high prevalence of infection

BACKGROUND

Anti-SARS-CoV-2 antibodies have been used in the study of the immune response in infected patients. However, differences in sensitivity and specificity have been reported, depending on the method of analysis. The aim of the present study was to evaluate the diagnostic accuracy of an algorithm in which a high-throughput automated assay for total antibodies was used for screening and two semi-automated IgG-specific methods were used to confirm the results, and also to correlate the analytical results with the clinical data and the time elapsed since infection.

METHODS

We studied 306 patients, some hospitalized and some outpatients, belonging to a population with a high prevalence of COVID-19. One-hundred and ten patients were classified as SARS-CoV-2 negative and 196 as positive by polymerase chain reaction.

RESULTS

The algorithm and automated assay alone had a specificity and a positive predictive value of 100%, although the sensitivity and negative predictive value of the algorithm was higher. Both methods showed a good sensitivity from day 11 of the onset of symptoms in asymptomatic and symptomatic patients. The absorbance of the total antibodies was significantly higher in severely symptomatic than in asymptomatic or mildly symptomatic patients, which suggests the antibody level was higher. We found 15 patients who did not present seroconversion at 12 days from the onset of symptoms or the first polymerase chain reaction test.

CONCLUSION

This study highlights the proper functioning of algorithms in the diagnosis of the immune response to COVID-19, which can help to define testing strategies against this disease.

Multicentre Performance Evaluation of the Elecsys Anti-SARS-CoV-2 Immunoassay as an Aid in Determining Previous Exposure to SARS-CoV-2

Introduction

We performed a multicentre evaluation of the Elecsys^® Anti-SARS-CoV-2 immunoassay (Roche Diagnostics), an assay utilising a recombinant protein representing the nucleocapsid (N) antigen, for the in vitro qualitative detection of antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Methods

Specificity was evaluated using serum/plasma samples from blood donors and routine diagnostic specimens collected before September 2019 (i.e., presumed negative for SARS-CoV-2-specific antibodies); sensitivity was evaluated using samples from patients with polymerase chain reaction (PCR)-confirmed SARS-CoV-2 infection. Point estimates and 95% confidence intervals (CIs) were calculated. Method comparison was performed versus commercially available assays.

Results

Overall specificity for the Elecsys Anti-SARS-CoV-2 immunoassay (n = 9575) was 99.85% (95% CI 99.75–99.92): blood donors (n = 6714; 99.82%), routine diagnostic specimens (n = 2861; 99.93%), pregnant women (n = 2256; 99.91%), paediatric samples (n = 205; 100.00%). The Elecsys Anti-SARS-CoV-2 immunoassay demonstrated significantly higher specificity versus LIAISON SARS-CoV-2 S1/S2 IgG (99.71% vs. 98.48%), EUROIMMUN Anti-SARS-CoV-2 IgG (100.00% vs. 94.87%), ADVIA Centaur SARS-CoV-2 Total (100.00% vs. 87.32%) and iFlash SARS-CoV-2 IgM (100.00% vs. 99.58%) assays, and comparable specificity to ARCHITECT SARS-CoV-2 IgG (99.75% vs. 99.65%) and iFlash SARS-CoV-2 IgG (100.00% vs. 100.00%) assays. Overall sensitivity for Elecsys Anti-SARS-CoV-2 immunoassay samples drawn at least 14 days post-PCR confirmation (n = 219) was 93.61% (95% CI 89.51–96.46). No statistically significant differences in sensitivity were observed between the Elecsys Anti-SARS-CoV-2 immunoassay versus EUROIMMUN Anti-SARS-CoV-2 IgG (90.32% vs. 95.16%) and ARCHITECT SARS-CoV-2 IgG (84.81% vs. 87.34%) assays. The Elecsys Anti-SARS-CoV-2 immunoassay showed significantly lower sensitivity versus ADVIA Centaur SARS-CoV-2 Total (85.19% vs. 95.06%) and iFlash SARS-CoV-2 IgG (86.25% vs. 93.75%) assays, but significantly higher sensitivity versus the iFlash SARS-CoV-2 IgM assay (86.25% vs. 33.75%).

Conclusion

The Elecsys Anti-SARS-CoV-2 immunoassay demonstrated very high specificity and high sensitivity in samples collected at least 14 days post-PCR confirmation of SARS-CoV-2 infection, supporting its use to aid in determination of previous exposure to SARS-CoV-2.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-021-00504-9.

Using Serologic Testing to Assess the Effectiveness of Outbreak Control Efforts, Serial Polymerase Chain Reaction Testing, and Cohorting of Positive Severe Acute Respiratory Syndrome Coronavirus 2 Patients in a Skilled Nursing Facility

We characterized serology following a nursing home outbreak where residents were serially tested by RT-PCR and positive residents were cohorted. When tested 46-76 days later, 24/26 RT-PCR-positive residents were seropositive; none of the 124 RT-PCR-negative residents had confirmed seropositivity, supporting serial SARS-CoV-2 RT-PCR testing and cohorting in nursing homes.

Low immunogenicity to SARS-CoV-2 vaccination among liver transplant recipients

BACKGROUND & AIMS

Two SARS-CoV-2 mRNA vaccines were approved to prevent COVID-19 infection, with reported vaccine efficacy of 95%. Liver transplant (LT) recipients are at risk of lower vaccine immunogenicity and were not included in the registration trials. We assessed vaccine immunogenicity and safety in this special population.

METHODS

LT recipients followed at the Tel-Aviv Sourasky Medical Center and healthy volunteers were tested for SARS-CoV-2 IgG antibodies directed against the Spike-protein (S) and Nucleocapsid-protein (N) 10-20 days after receiving the second Pfizer-BioNTech BNT162b2 SARS-CoV-2 vaccine dose. Information regarding vaccine side effects and clinical data was collected from patients and medical records.

RESULTS

Eighty LT recipients were enrolled. Mean age was 60 years and 30% were female. Twenty-five healthy volunteer controls were younger (mean age 52.7 years, p = 0.013) and mostly female (68%, p = 0.002). All participants were negative for IgG N-protein serology, indicating immunity did not result from prior COVID-19 infection. All controls were positive for IgG S-protein serology. Immunogenicity among LT recipients was significantly lower with positive serology in only 47.5% (p <0.001). Antibody titer was also significantly lower in this group (mean 95.41 AU/ml vs. 200.5 AU/ml in controls, p <0.001). Predictors for negative response among LT recipients were older age, lower estimated glomerular filtration rate, and treatment with high dose steroids and mycophenolate mofetil. No serious adverse events were reported in either group.

CONCLUSION

LT recipients developed substantially lower immunological response to the Pfizer-BioNTech SARS-CoV-2 mRNA-based vaccine. Factors influencing serological antibody responses include age, renal function and immunosuppressive medications. The findings require re-evaluation of vaccine regimens in this population.

LAY SUMMARY

The Pfizer-BioNTech BNT162b2 SARS-CoV-2 vaccine elicited substantially inferior immunity in liver transplant recipients. Less than half of the patients developed sufficient levels of antibodies against the virus, and in those who were positive, average antibody levels were 2x less compared to healthy controls. Factors predicting non-response were older age, renal function and immunosuppressive medications.

Reduced humoral response to mRNA SARS-CoV-2 BNT162b2 vaccine in kidney transplant recipients without prior exposure to the virus

COVID-19 is associated with increased morbidity and mortality in transplant recipients. There are no efficacy data available regarding these patients with any of the available SARS-CoV-2 vaccines. We analyzed the humoral response following full vaccination with the BNT162b2 (Pfizer-BioNTech) in 136 kidney transplant recipients, and compared it to 25 controls. In order to exclude prior exposure to the virus, only participants with negative serology to SARS-CoV-2 nucleocapsid protein were included. All controls developed a positive response to spike protein, while only 51 of 136 transplant recipients (37.5%) had positive serology (p < .001). Mean IgG anti-spike level was higher in the controls (31.05 [41.8] vs. 200.5 [65.1] AU/mL, study vs. control, respectively, p < .001). Variables associated with null humoral response were older age (odds ratio 1.66 [95% confidence interval 1.17-2.69]), high-dose corticosteroids in the last 12 months (1.3 [1.09-1.86]), maintenance with triple immunosuppression (1.43 [1.06-2.15]), and regimen that includes mycophenolate (1.47 [1.26-2.27]). There was a similar rate of side effects between controls and recipients, and no correlation was found between the presence of symptoms and seroconversion. Our findings suggest that most kidney transplant recipients remain at high risk for COVID-19 despite vaccination. Further studies regarding possible measures to increase recipient's response to vaccination are required.

Usefulness of IVD Kits for the Assessment of SARS-CoV-2 Antibodies to Evaluate the Humoral Response to Vaccination

Background: The introduction of the vaccination against SARS-CoV-2 infection creates the need for precise tools for the quality control of vaccination procedures, detection of poor humoral response, and estimation of the achieved protection against the disease. Thus, the study aimed to compare the results of the anti-SARS-CoV-2 tests to evaluate the application of the WHO standard unitage (the binding antibody units; BAU/mL) for a measurement of response to the vaccination. Methods: Patients undergoing vaccination against SARS-CoV-2 with Pfizer/BioNTech BNT162b2 (BNT162b2) (n = 79), referred for SARS-CoV-2 antibody measurement prior to vaccination and 21 days after dose 1, and 8, 14, and 30 days after dose 2 were included. The sera were tested with three assays: Elecsys SARS-CoV-2 S (Roche), LIAISON^® SARS-CoV-2 TrimericS IgG (DiaSorin), and SARS-CoV-2 IgG II Quant (Abbott). Results: The three assays showed varying correlations at different time points in the study. The overall agreement for all samples was moderate to high (ρ = 0.663–0.902). We observed the most uniform agreement for the day of dose 2 (ρ = 0.775–0.825), while it was least consistent for day 8 (ρ = −0.131–0.693) and 14 (ρ = −0.247–0.603) after dose 2. The dynamics of changes of the SARS-CoV-2 antibody levels in patients without history of prior SARS-CoV-2 infection appears homogenous based on the Roche results, more heterogenous when considering the DiaSorin results, and in between for the Abbott results. Conclusions: The results highlight the need for further work on the international standard of measurement of SARS-CoV-2 Ig, especially in the era of vaccination. The serological assays can be useful to detect IgG/IgM antibodies to assess the response to the vaccination. However, they cannot be used interchangeably. In terms of the evaluation of the immune response to the BNT162b2 vaccine, Roche and Abbott kits appear to be more useful.