SARS-CoV-2-specific T cell responses: a comparative analysis between QuantiFERON SARS-CoV-2, T-SPOT.COVID, and an in-house Omicron ELISpot.

BACKGROUND: T cell immunity plays a pivotal role in mitigating the severity of coronavirus disease 2019 (COVID-19). Therefore, reliable functional T cell assays are required to evaluate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T cell immunity in specific patient populations. METHODS: We recruited a cohort of 23 healthcare workers who received their bivalent Omicron BA.1 / ancestral mRNA booster vaccination or were infected with the Omicron variant at a median of 144 days and 227 days before blood collection, respectively. In this cohort, we compared the performances of two widely utilized commercial SARS-CoV-2 interferon-gamma release assays (IGRAs), i.e., QuantiFERON SARS-CoV-2 and T-SPOT.COVID, and an in-house designed Omicron enzyme-linked immunospot (ELISpot). RESULTS: The QuantiFERON SARS-CoV-2 and T-SPOT.COVID assays detected SARS-CoV-2 spike-specific T cells in 34.8% and 21.7% of participants, respectively. Moreover, our in-house designed ELISpot that included Omicron BA.4 and BA.5 full-spike peptides detected T cell responses in 47.8% of participants and was strongly associated with the T-SPOT.COVID. CONCLUSION: The evaluation of SARS-CoV-2 T cell immunity using commercially accessible assays may yield disparate outcomes as results from different assays are not directly comparable. A specific Omicron ELISpot should be considered to assess Omicron-specific T cell immunity.

Correction: COVID-19 Vaccine-Induced Myocarditis and Pericarditis: Towards Identification of Risk Factors.

[This corrects the article DOI: 10.5334/gh.1252.].

Evaluation of a New Standardized Nasal Sampling Method for Detection of SARS-CoV-2 RNA via RT-PCR.

The aim of this study was to compare the diagnostic accuracy of nasal sampling using a novel anterior nasal swab (ANS) (Rhinoswab) versus combined oro-nasopharyngeal (OP/NP) sampling in COVID-19 suspected patients. This prospective observational study was performed from 11 November to 2 December 2021 (part 1), and from 16 January to 22 February 2022 (part 2). Adult patients who attended the emergency room with suspected COVID-19 were asked to participate. One ANS and one OP/NP sample were consecutively collected, and both were analyzed via reverse transcription polymerase chain reaction (RT-PCR). The result of the OP/NP sample was considered to be the reference standard. A total of 412 patients were included, of whom 171 (41.5%) had a positive RT-PCR of the OP/NP swab, whereas 139 (33.7%) were positive on the ANS sample. The overall diagnostic accuracy for ANS sampling in terms of sensitivity, specificity, positive predictive value, and negative predictive value was 80.7% (95% CI 73.8-86.2), 99.6% (95% CI 97.3-100), 99.3% (95% CI 95.5-100), and 87.9% (95% CI 83.3-91.4), respectively. In conclusion, ANS sampling with the Rhinoswab identified 80.7% of all presented COVID-19 patients in an emergency department. Future studies should investigate if nasal Rhinoswab self-sampling is suitable for reliable diagnosis of COVID-19 in an outpatient setting.

Ancestral SARS-CoV-2 and Omicron BA.5-specific neutralizing antibody and T-cell responses after Omicron bivalent booster vaccination in previously infected and infection-naive individuals.

Coronavirus disease-2019 (COVID-19) bivalent ancestral/Omicron messenger RNA (mRNA) booster vaccinations became available to boost and expand the immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron infections. In a prospective cohort study including 59 healthcare workers, we assessed SARS-CoV-2 ancestral and Omicron BA.5-specific neutralizing antibody and T-cell responses in previously infected and infection-naive individuals. Also, we assessed the effect of an ancestral/Omicron BA.1 bivalent mRNA booster vaccination on these immune responses. 10 months after previous monovalent mRNA vaccinations, ancestral SARS-CoV-2 S1-specific T-cell and anti-RBD IgG responses remained detectable in most individuals and a previous SARS-CoV-2 infection was associated with increased T-cell responses. T-cell responses, anti-RBD IgG, and Omicron BA.5 neutralization activity increased after receiving an ancestral/Omicron BA.1 bivalent booster mRNA vaccination. An Omicron BA.5 infection in addition to bivalent vaccination, led to a higher ratio of Omicron BA.5 to ancestral strain neutralization activity compared to no bivalent vaccination and no recent SARS-CoV-2 infection. In conclusion, SARS-CoV-2 T-cell and antibody responses persist for up to 10 months after a monovalent booster mRNA vaccination. An ancestral/Omicron BA.1 bivalent booster mRNA vaccination increases these immune responses and also induces Omicron BA.5 cross-neutralization antibody activity. Finally, our data indicate that hybrid immunity is associated with improved preservation of T-cell immunity.

Airborne virus shedding of the alpha, delta, omicron SARS-CoV-2 variants and influenza virus in hospitalized patients.

Airborne transmission is an important transmission route for the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Epidemiological data indicate that certain SARS-CoV-2 variants, like the omicron variant, are associated with higher transmissibility. We compared virus detection in air samples between hospitalized patients infected with different SARS-CoV-2 variants or influenza virus. The study was performed during three separate time periods in which subsequently the alpha, delta, and omicron SARS-CoV-2 variants were predominant. In total, 79 patients with coronavirus disease 2019 (COVID-19) and 22 patients with influenza A virus infection were included. Collected air samples were positive in 55% of patients infected with the omicron variant in comparison to 15% of those infected with the delta variant (p < 0.01). In multivariable analysis, the SARS-CoV-2 omicron BA.1/BA.2 variant (as compared to the delta variant) and the viral load in nasopharynx were both independently associated with air sample positivity, but the alpha variant and COVID-19 vaccination were not. The proportion of positive air samples patients infected with the influenza A virus was 18%. In conclusion, the higher air sample positivity rate of the omicron variant compared to previous SARS-CoV-2 variants may partially explain the higher transmission rates seen in epidemiological trends.

Performance of point-of care molecular and antigen-based tests for SARS-CoV-2: a living systematic review and meta-analysis.

BACKGROUND: Molecular and antigen point-of-care tests (POCTs) have augmented our ability to rapidly identify and manage SARS-CoV-2 infection. However, their clinical performance varies among individual studies. OBJECTIVES: The evaluation of the performance of molecular and antigen-based POCTs in confirmed, suspected, or probable COVID-19 cases compared with that of laboratory-based RT-PCR in real-life settings. DATA SOURCES: MEDLINE/PubMed, Scopus, Embase, Web of Science, Cochrane Library, Cochrane COVID-19 study register, and COVID-19 Living Evidence Database from the University of Bern. STUDY ELIGIBILITY CRITERIA: Peer-reviewed or preprint observational studies or randomized controlled trials that evaluated any type of commercially available antigen and/or molecular POCTs for SARS-CoV-2, including multiplex PCR panels, approved by the United States Food and Drug Administration, with Emergency Use Authorization, and/or marked with Conformitè Europëenne from European Commission/European Union. PARTICIPANTS: Close contacts and/or patients with symptomatic and/or asymptomatic confirmed, suspected, or probable COVID-19 infection of any age. TEST/S: Molecular and/or antigen-based SARS-CoV-2 POCTs. REFERENCE STANDARD: Laboratory-based SARS-CoV-2 RT-PCR. ASSESSMENT OF RISK OF BIAS: Eligible studies were subjected to quality-control and risk-of-bias assessment using the Quality Assessment of Diagnostic Accuracy Studies 2 tool. METHODS OF DATA SYNTHESIS: Summary sensitivities and specificities with their 95% CIs were estimated using a bivariate model. Subgroup analysis was performed when at least three studies informed the outcome. RESULTS: A total of 123 eligible publications (97 and 26 studies assessing antigen-based and molecular POCTs, respectively) were retrieved from 4674 initial records. The pooled sensitivity and specificity for 13 molecular-based POCTs were 92.8% (95% CI, 88.9-95.4%) and 97.6% (95% CI, 96.6-98.3%), respectively. The sensitivity of antigen-based POCTs pooled from 138 individual evaluations was considerably lower than that of molecular POCTs; the pooled sensitivity and specificity rates were 70.6% (95% CI, 67.2-73.8%) and 98.9% (95% CI, 98.5-99.2%), respectively. DISCUSSION: Further studies are needed to evaluate the performance of molecular and antigen-based POCTs in underrepresented patient subgroups and different respiratory samples.

Dynamics of Antibody and T Cell Immunity against SARS-CoV-2 Variants of Concern and the Impact of Booster Vaccinations in Previously Infected and Infection-Naïve Individuals.

Despite previous coronavirus disease 2019 (COVID-19) vaccinations and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections, SARS-CoV-2 still causes a substantial number of infections due to the waning of immunity and the emergence of new variants. Here, we assessed the SARS-CoV-2 spike subunit 1 (S1)-specific T cell responses, anti-SARS-CoV-2 receptor-binding domain (RBD) IgG serum concentrations, and the neutralizing activity of serum antibodies before and one, four, and seven months after the BNT162b2 or mRNA-1273 booster vaccination in a cohort of previously infected and infection-naïve healthcare workers (HCWs). Additionally, we assessed T cell responses against the spike protein of the SARS-CoV-2 Delta, Omicron BA.1 and BA.2 variants of concern (VOC). We found that S1-specific T cell responses, anti-RBD IgG concentrations, and neutralizing activity significantly increased one month after booster vaccination. Four months after booster vaccination, T cell and antibody responses significantly decreased but levels remained steady thereafter until seven months after booster vaccination. After a similar number of vaccinations, previously infected individuals had significantly higher S1-specific T cell, anti-RBD IgG, and neutralizing IgG responses than infection-naïve HCWs. Strikingly, we observed overall cross-reactive T cell responses against different SARS-CoV-2 VOC in both previously infected and infection-naïve HCWs. In summary, COVID-19 booster vaccinations induce strong T cell and neutralizing antibody responses and the presence of T cell responses against SARS-CoV-2 VOC suggest that vaccine-induced T cell immunity offers cross-reactive protection against different VOC.

An international observational study to assess the impact of the Omicron variant emergence on the clinical epidemiology of COVID-19 in hospitalised patients.

Background: Whilst timely clinical characterisation of infections caused by novel SARS-CoV-2 variants is necessary for evidence-based policy response, individual-level data on infecting variants are typically only available for a minority of patients and settings. Methods: Here, we propose an innovative approach to study changes in COVID-19 hospital presentation and outcomes after the Omicron variant emergence using publicly available population-level data on variant relative frequency to infer SARS-CoV-2 variants likely responsible for clinical cases. We apply this method to data collected by a large international clinical consortium before and after the emergence of the Omicron variant in different countries. Results: Our analysis, that includes more than 100,000 patients from 28 countries, suggests that in many settings patients hospitalised with Omicron variant infection less often presented with commonly reported symptoms compared to patients infected with pre-Omicron variants. Patients with COVID-19 admitted to hospital after Omicron variant emergence had lower mortality compared to patients admitted during the period when Omicron variant was responsible for only a minority of infections (odds ratio in a mixed-effects logistic regression adjusted for likely confounders, 0.67 [95% confidence interval 0.61-0.75]). Qualitatively similar findings were observed in sensitivity analyses with different assumptions on population-level Omicron variant relative frequencies, and in analyses using available individual-level data on infecting variant for a subset of the study population. Conclusions: Although clinical studies with matching viral genomic information should remain a priority, our approach combining publicly available data on variant frequency and a multi-country clinical characterisation dataset with more than 100,000 records allowed analysis of data from a wide range of settings and novel insights on real-world heterogeneity of COVID-19 presentation and clinical outcome. Funding: Bronner P. Gonçalves, Peter Horby, Gail Carson, Piero L. Olliaro, Valeria Balan, Barbara Wanjiru Citarella, and research costs were supported by the UK Foreign, Commonwealth and Development Office (FCDO) and Wellcome [215091/Z/18/Z, 222410/Z/21/Z, 225288/Z/22/Z]; and Janice Caoili and Madiha Hashmi were supported by the UK FCDO and Wellcome [222048/Z/20/Z]. Peter Horby, Gail Carson, Piero L. Olliaro, Kalynn Kennon and Joaquin Baruch were supported by the Bill & Melinda Gates Foundation [OPP1209135]; Laura Merson was supported by University of Oxford's COVID-19 Research Response Fund - with thanks to its donors for their philanthropic support. Matthew Hall was supported by a Li Ka Shing Foundation award to Christophe Fraser. Moritz U.G. Kraemer was supported by the Branco Weiss Fellowship, Google.org, the Oxford Martin School, the Rockefeller Foundation, and the European Union Horizon 2020 project MOOD (#874850). The contents of this publication are the sole responsibility of the authors and do not necessarily reflect the views of the European Commission. Contributions from Srinivas Murthy, Asgar Rishu, Rob Fowler, James Joshua Douglas, François Martin Carrier were supported by CIHR Coronavirus Rapid Research Funding Opportunity OV2170359 and coordinated out of Sunnybrook Research Institute. Contributions from Evert-Jan Wils and David S.Y. Ong were supported by a grant from foundation Bevordering Onderzoek Franciscus; and Andrea Angheben by the Italian Ministry of Health "Fondi Ricerca corrente-L1P6" to IRCCS Ospedale Sacro Cuore-Don Calabria. The data contributions of J.Kenneth Baillie, Malcolm G. Semple, and Ewen M. Harrison were supported by grants from the National Institute for Health Research (NIHR; award CO-CIN-01), the Medical Research Council (MRC; grant MC_PC_19059), and by the NIHR Health Protection Research Unit (HPRU) in Emerging and Zoonotic Infections at University of Liverpool in partnership with Public Health England (PHE) (award 200907), NIHR HPRU in Respiratory Infections at Imperial College London with PHE (award 200927), Liverpool Experimental Cancer Medicine Centre (grant C18616/A25153), NIHR Biomedical Research Centre at Imperial College London (award IS-BRC-1215-20013), and NIHR Clinical Research Network providing infrastructure support. All funders of the ISARIC Clinical Characterisation Group are listed in the appendix.

Comparative clinical manifestations and immune effects of cytomegalovirus infections following distinct types of immunosuppression.

BACKGROUND: Cytomegalovirus (CMV) infection is a well-recognised complication of solid organ and hematopoietic cell transplantation. However, CMV infection also occurs in patients with human immunodeficiency virus infection, previously immunocompetent intensive care unit patients, and individuals on immunosuppressive medications for various underlying diseases. OBJECTIVES: This review describes the comparative effects of CMV infection in distinct types of acquired immunosuppression. SOURCES: Selected peer-reviewed publications on CMV infections published until December 2021. CONTENT: CMV infection affects various organ systems through direct cytolytic mechanisms but may also exert indirect effects by promoting pro-inflammatory and immunosuppressive responses. This has been well studied in transplant recipients, for whom antiviral prophylaxis and pre-emptive therapy have now become standard practice. These strategies not only prevent direct CMV disease manifestations but also mitigate various immunopathological processes to reduce graft-vs.-host disease, graft rejection, and the occurrence of secondary bacterial and fungal infections. The efficacy of neither prophylactic nor pre-emptive treatment of CMV infection has been demonstrated for patients with critical illness- or medication-induced immunosuppression. Many observational studies have shown an independent association between CMV reactivation and a prolonged duration of mechanical ventilation or increased mortality in the intensive care unit. Furthermore, data suggest that CMV reactivation may increase pulmonary inflammation and prolong the duration of mechanical ventilation. IMPLICATIONS: A large number of observational and experimental studies suggest attributable morbidity and mortality related to CMV infection, not only in transplant recipients and patients with human immunodeficiency virus infection but also in patients with critically illness- or medication-induced immunosuppression. Adequately powered randomised controlled trials investigating the efficacy of prophylaxis or pre-emptive treatment of CMV infection in these patients are lacking, with a notable exception for transplant recipients.

ESCMID guidelines on testing for SARS-CoV-2 in asymptomatic individuals to prevent transmission in the health care setting.

SCOPE: This guideline addresses the indications for direct testing of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in asymptomatic individuals in health care facilities, with the aim to prevent SARS-CoV-2 transmissions in these settings. The benefit of testing asymptomatic individuals to create a safe environment for patients and health care workers must be weighed against potential unintended consequences, including delaying necessary treatments owing to false positive results and lower quality of care owing to strict isolation measures. METHODS: A total of nine PICOs (population, intervention, comparison, outcome) on the topic of testing asymptomatic individuals was selected by the panel members. Subsequently, a literature search for existing guidelines and systematic reviews was performed on PubMed, Epistemonikos, and RecMap using relevant filters available in each database. Data on article/recommendation type, setting, target population, intervention, and quality of the evidence were extracted. Credibility of the systematic reviews was evaluated using the AMSTAR tool, and level of agreement with available recommendation was evaluated with the AGREE II score. Because the evidence available from systematic reviews was deemed insufficiently updated to formulate relevant recommendations, an additional search targeting relevant guidance documents from major public health institutions and original studies was performed. Provisional recommendations were discussed via web conferences until agreement was reached, and final recommendations were formulated according to the GRADE approach. RECOMMENDATIONS: Recommendations were formulated regarding systematic testing in asymptomatic individuals upon admission to a health care setting, during hospital stay, before elective procedures, and before scheduled nonsurgical procedures. Moreover, recommendations regarding testing of asymptomatic visitors, personal caregivers, and health care workers in health care facilities were presented. Recommendations also were given on contact tracing in asymptomatic patients or health care workers and the possibility of a negative screening test to shorten the quarantine period. Furthermore, if applicable, recommendations were specified to transmission rate and vaccination coverage.

Etiology of Myocardial Injury in Critically Ill Patients with Sepsis: A Cohort Study.

Rationale: Myocardial injury occurs frequently during sepsis and is independently associated with mortality. However, its etiology remains largely unknown. Objectives: To assess the relative contributions of hyperinflammation, activated coagulation, and endothelial dysfunction to myocardial injury in critically ill patients with sepsis. Methods: We included consecutive patients with sepsis presenting to two tertiary intensive care units in the Netherlands between 2011 and 2013. High-sensitivity cardiac troponin I as well as a wide range of plasma biomarkers related to inflammation, coagulation, and endothelial function were measured. Structural equation modeling was used to construct latent variables representing each of these pathophysiological constructs and to subsequently study their associations with troponin elevation while adjusting for confounders. Results: We analyzed 908 (88%) of 1,037 eligible patients, 553 (61%) of whom had raised high-sensitivity cardiac troponin I levels upon intensive care unit admission. The latent variables included interleukin (IL)-6, IL-8, and IL-1ß for inflammation; platelet count, prothrombin time, and protein C for coagulation; and soluble E-selectin, intercellular adhesion molecule-1, and angiopoietin-2 for endothelial function. After adjustment for age and cardiovascular comorbidities, structural equation modeling analysis showed that activated coagulation was independently associated with elevated troponin during sepsis (standardized regression coefficient, 0.551; 95% confidence interval [CI], 0.257-0.845; P < 0.001) whereas hyperinflammation and endothelial dysfunction were not (standardized regression coefficient, -0.161; 95% CI, -0.418 to 0.096 and -0.054; 95% CI, -0.168 to 0.060, respectively). Conclusions: Our findings suggest that myocardial injury during sepsis is mediated by systemic activation of coagulation rather than by circulating inflammatory mediators or activation of the endothelium. These findings may guide evaluation of strategies to protect the myocardium during sepsis. Clinical trial registered with clinicaltrials.gov (NCT01905033).

SARS-CoV-2 antibody and T cell responses one year after COVID-19 and the booster effect of vaccination: A prospective cohort study.

OBJECTIVES: First, to describe SARS-CoV-2 T cell and antibody responses in a prospective cohort of healthcare workers that suffered from mild to moderate COVID-19 approximately one year ago. Second, to assess COVID-19 vaccine-induced immune responses in these prior-infected individuals. METHODS: SARS-CoV-2-specific T cell and anti-SARS-CoV-2-Spike-RBD immunoglobulin G (IgG) responses in blood were determined before COVID-19 vaccination with mRNA-1273, BNT162b2, Ad26.CoV2-S or ChAdOx1-S, two weeks after first vaccination, and after second vaccination. RESULTS: 55 prior SARS-CoV-2 infected and seroconverted individuals were included. S1-specific T cell responses and anti-RBD IgG were detectable one year post SARS-CoV-2 infection: 24 spot-forming cells per 106 peripheral blood mononuclear cells (SFCs/106 PBMCs) after S1 stimulation and anti-RBD IgG concentration of 74 (IQR 36-158) IU/mL. Responses after the first and second vaccination were comparable with S1-specfic T cell responses of 198 (IQR 137-359) and 180 (IQR 103-347) SFCs/106 PBMCs, and IgG concentrations of 6792 (IQR 3386-15,180) and 6326 (IQR 2336-13,440) IU/mL, respectively. These responses retained up to four months after vaccination. CONCLUSIONS: Both T cell and IgG responses against SARS-CoV-2 persist for up to one year after COVID-19. A second COVID-19 vaccination in prior-infected individuals did not further increase immune responses in comparison to one vaccination.

Development of an in-house SARS-CoV-2 interferon-gamma ELISpot and plate reader-free spot detection method.

Coronavirus disease 2019 (COVID-19) vaccination programs rolled out in an attempt to stop the COVID-19 pandemic. Besides neutralising antibodies, effective T cell responses are also crucial for protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and COVID-19 disease severity. To assess SARS-CoV-2-specific T cell immunity, we developed an interferon-gamma (IFN-γ) enzyme-linked immunospot (ELISpot) that can be deployed in research and diagnostic settings. We optimised our ELISpot by testing multiple antigen concentrations to stimulate peripheral blood mononuclear cells of SARS-CoV-2-unexposed, COVID-19 convalescent and COVID-19 vaccinated volunteers. Also, we developed an ELISpot plate reader-free method to detect and quantify spots, which we compared to manual spot counting and automated analysis by an ELISpot plate reader. We observed strong SARS-CoV-2-reactive T cell responses in COVID-19 convalescent, and COVID-19 vaccinated volunteers but absent or only weak responses in unexposed volunteers. Overall, antigens with concentrations from 0.1 to 5.0 µg/mL per peptide elicited similar T cell responses. Also, our plate reader-free detection method reliably detected and quantified SARS-CoV-2-specific T cells, demonstrated by an excellent reliability when compared to manual analysis and automated analysis by an ELISpot plate reader.

Painful and swollen tongue: mucosal leishmaniasis due to Leishmania infantum.

BACKGROUND: Leishmaniasis is a parasitic disease caused by different Leishmania species. L. infantum is found in the Mediterranean area. It usually causes visceral or cutaneous leishmaniasis, but rarely mucosal leishmaniasis (ML). METHODS: A 62-year-old man with metastatic non-small-cell lung carcinoma visited the outpatient clinic because of a painful and swollen tongue. Initially, oral candidiasis was suspected and patient was unsuccessfully treated accordingly. Subsequently, a biopsy from the tongue was taken. RESULTS: Histology of the tongue biopsy showed an inflammation with histiocytes and Leishmania amastigotes. Molecular analysis determined these parasites as L. donovani complex. Based on the patient's travel history, ML caused by L. infantum was diagnosed. CONCLUSION: ML is an unusual presentation of L. infantum. ML is not only caused by Leishmania species endemic in Latin America, but also should be considered in the differential diagnosis for European patients. A biopsy of the affected location is needed to confirm the diagnosis.

SARS-CoV-2 antibody response dynamics and heterogeneous diagnostic performance of four serological tests and a neutralization test in symptomatic healthcare workers with non-severe COVID-19.

BACKGROUND: Most COVID-19 patients experience non-severe illness. The presence of SARS-CoV-2 antibodies suggest possible protection against re-infections in prior SARS-CoV-2 infected individuals. OBJECTIVES: The aims of this prospective observational study were to longitudinally assess the antibody response during the first 4-6 months after polymerase chain reaction (PCR) confirmed SARS-CoV-2 infection, and to study the diagnostic performance of four different enzyme-linked immunosorbent assays (ELISAs) and a surrogate virus neutralization test (sVNT) in symptomatic healthcare workers (HCWs) with non-severe COVID-19. STUDY DESIGN: HCWs in a teaching hospital were included between March 8 and June 15, 2020, when they had a PCR-confirmed SARS-CoV-2 infection in the past 3 months. The performances of four ELISAs (Wantai, Bio-Rad Platelia, BioTrading Immy clarus, and Euroimmun) were evaluated in serum samples obtained at the moment of study inclusion and subsequently at 1, 2 and 3 months thereafter. Furthermore, in the last available serum sample sVNT by GenScript was performed. RESULTS: 309 samples from 80 positive HCWs were included of whom 70 (88%) were SARS-CoV-2 seropositive. The detection rates of SARS-CoV-2 antibodies by the different ELISAs were heterogenous ranging from 64% for the Euroimmun ELISA to 88% for the Wantai ELISA. The Wantai ELISA had the highest and almost perfect agreement with sVNT (96%, Cohen's kappa 0.83). CONCLUSION: SARS-CoV-2 (neutralizing) antibodies were detectable in most symptomatic individuals with non-severe COVID-19. The presence of antibodies remained stable up to six months after initial infection. There is large variability in diagnostic test performance between ELISA tests.

Rapid screening method for the detection of SARS-CoV-2 variants of concern.

BACKGROUND: Comprehensive and up-to-date monitoring of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOC) is crucial as these are characterized by their increased transmissibility, immune evasion and virulence. OBJECTIVES: To describe the wide-scale implementation of a reverse transcriptase polymerase chain reaction (RT-PCR) multiple variants assay with melting curve analysis as a routine procedure. STUDY DESIGN: We prospectively performed multiple variants RT-PCR on consecutive SARS-CoV-2 RT-PCR positive samples from patients, healthcare workers and nursing home residents from our hospital catchment area. This technique was implemented in our automated Roche FLOW system with a turn-around time of 6 h. RESULTS: Between February 1 and May 2, 2021, 989 samples were tested by the variant RT-PCR. Our method was validated by comparison of variant RT-PCR to whole genome sequencing testing. We observed an increase over time in the proportion of UK variant that became the dominant variant, and the concurrent emergence of the South-African and Brazilian variants. Prompt public health responses for infection control were possible because of this rapid screening method, resulting in early detection and reduction of unnoticed spread of VOC as early as possible. CONCLUSION: A variant RT-PCR with additional melting curve analyses is a feasible, rapid and efficient screening strategy that can be implemented in routine microbiological laboratories.