SARS-CoV-2 seroprevalence study after the first wave among persons living and working in an overcrowded Swiss prison.

PURPOSE: Prisons can be epicentres of infectious diseases. However, empirical evidence on the impact of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic in prison is still scarce. This study aims to estimate the seroprevalence rates of anti-SARS-CoV-2 in the largest and most crowded Swiss prison and compare them with the seroprevalence rate in the general population. DESIGN/METHODOLOGY/APPROACH: A cross-sectional study was conducted in June 2020, one month after the first wave of SARS-CoV-2 in Switzerland. Groups included: people living in detention (PLDs) detained before the beginning of the pandemic (n = 116), PLDs incarcerated after the beginning of the pandemic (n = 61), prison staff and prison healthcare workers (n = 227) and a sample from the general population in the same time period (n = 3,404). The authors assessed anti-SARS-CoV-2 IgG antibodies. FINDINGS: PLDs who were incarcerated before the beginning of the pandemic had a significantly lower seroprevalence rate [0.9%, confidence interval (CI)95%: 0.1%-5.9%] compared to the general population (6.3%, CI 95%: 5.6-7.3%) (p = 0.041). The differences between PLDs who were incarcerated before and other groups were marginally significant (PLDs incarcerated after the beginning of the pandemic: 6.6%, CI 95%: 2.5%-16.6%, p = 0.063; prison staff CI 95%: 4.8%, 2.7%-8.6%, p = 0.093). The seroprevalence of prison staff was only slightly and non-significantly lower than that of the general population. ORIGINALITY/VALUE: During the first wave, despite overcrowding and interaction with the community, the prison was not a hotspot of SARS-CoV-2 infection. Preventive measures probably helped avoiding clusters of infection. The authors suggest that preventive measures that impact social welfare could be relaxed when overall circulation in the community is low to prevent the negative impact of isolation.

Feasibility of home-based ELISA capillary blood self-testing for anti-SARS-CoV-2 antibodies.

Objectives: Serological assays for the presence of anti-SARS-CoV-2 antibodies are crucially needed for research and monitoring of the SARS-CoV-2 pandemic. Antibodies are reliability detected in capillary blood, a minimally invasive and cost-effective alternative to venous blood testing. However, there is a limited knowledge on feasibility of capillary blood self-sampling. This study compared the feasibility of capillary blood self-testing in people aged less than 65 vs. people aged 65 or more. A secondary aim was to investigate the performance of the Hem-Col® (no additive) device compared to venous blood testing. Design and methods: Data were collected in a prospective study in Switzerland (n = 106). Capillary blood was collected using the Hem-Col® (no additive) device. Feasibility was assessed using 1) collecting the recommended amount of capillary blood and 2) achieving all steps of capillary blood collection. A sample of 5 ml of venous blood was also collected. Results: For the primary objective, 86.2%/62.1% of patients aged less than 65 collected the recommended amount of capillary blood/achieved all steps vs. 62.5%/39.6% of patients aged 65 or more (p = .006/p = .022). For the secondary objective, the correlation between capillary and venous blood was r = 0.992 and kappa = 1. Conclusions: Capillary blood self-testing appeared as a feasible and reliable alternative to venous blood testing. Such alternative would improve access to serological testing and spare health care resources. However, the difference between age groups should be considered when using self-sampling devices. Help should be developed for older people, such as phone counseling or encouraging asking younger family members for help.

A Comparative Study of Nine SARS-CoV-2 IgG Lateral Flow Assays Using Both Post-Infection and Post-Vaccination Samples.

BACKGROUND: Since the SARS-CoV-2 pandemic, lateral flow assays (LFA) detecting specific antibodies have entered the market in abundance. Despite being CE-IVD-labeled, the antigenic compounds of the assays are often unknown, the performance characteristics provided by the manufacturer are often incomplete, and the samples used to obtain the data are not detailed. OBJECTIVE: To perform a comparative evaluation of nine lateral flow assays to detect IgG responses against SARS-CoV-2. For the evaluation, a carefully designed serum panel containing post-infection samples and post-vaccination (both mRNA vaccine and inactivated virus vaccine) samples was used. RESULTS: The sensitivity of the assays overall ranged from 9 to 90.3% and the specificity ranged from 94.2 to 100%. Spike protein-containing assays performed generally better than the assays with only nucleocapsid protein. The sensitivity of some assays was higher on post-infection samples, while other assays had a higher sensitivity to post-vaccination samples. CONCLUSION: A comparative approach in the verification of LFAs with an adequately designed serum panel enabled the identification of the antigens used in the assays. Sensitivities differed between post-infection and post-vaccination samples, depending on the assays used. This demonstrates that the verification of assays must be performed with samples representative of the intended use of the assay.

Head-to-Head Evaluation of Five Automated SARS-CoV-2 Serology Immunoassays in Various Prevalence Settings.

PURPOSE: To assess the diagnostic performances of five automated anti-SARS-CoV-2 immunoassays, Epitope (N), Diasorin (S1/S2), Euroimmun (S1), Roche N (N), and Roche S (S-RBD), and to provide a testing strategy based on pre-test probability. METHODS: We assessed the receiver operating characteristic (ROC) areas under the curve (AUC) values, along with the sensitivity, specificity, positive predictive values (PPVs), and negative predictive values (NPVs), of each assay using a validation sample set of 172 COVID-19 sera and 185 negative controls against a validated S1-immunofluorescence as a reference method. The three assays displaying the highest AUCs were selected for further serodetection of 2033 sera of a large population-based cohort. RESULTS: In the validation analysis (pre-test probability: 48.1%), Roche N, Roche S and Euroimmun showed the highest discriminant accuracy (AUCs: 0.99, 0.98, and 0.98) with PPVs and NPVs above 96% and 94%, respectively. In the population-based cohort (pre-test probability: 6.2%) these three assays displayed AUCs above 0.97 and PPVs and NPVs above 90.5% and 99.4%, respectively. A sequential strategy using an anti-S assay as screening test and an anti-N as confirmatory assays resulted in a 96.7% PPV and 99.5% NPV, respectively. CONCLUSIONS: Euroimmun and both Roche assays performed equally well in high pre-test probability settings. At a lower prevalence, sequentially combining anti-S and anti-N assays resulted in the optimal trade-off between diagnostic performances and operational considerations.