SARS-CoV-2 Seroprevalence and Accuracy Diagnostic Evaluation During a Covid-19 Outbreak in a Major Penitentiary Complex in Brazil, June-July 2020: A Population-Based Study (preprint)

ABSTRACT

Summary: The pandemic of COVID-19 has presented as a threat to prison systems worldwide, as overcrowding, limited possibility of social distancing and sanitary restrictions favouring viral spread. SARS-CoV-2 seroprevalence studies in prison settings are important tools to understand transmission and to develop control measures. We aimed to estimate the overall SARS-CoV-2 seroprevalence and evaluated the accuracy of an antibody rapid test compared to a reference serological assay during a COVID-19 outbreak in a prison complex housing over 13,000 inmates in Brasília. Methods: We conducted a repeated serosurvey of IgM/IgG SARS-CoV-2 antibodies among inmates between June 17-July 1 (baseline) and July 8-22, 2020 (21-days follow-up). We obtained a randomized, stratified representative sample of each prison unit. Inmates who accepted to be part of the study were interviewed through a standardised questionnaire covering sociodemographic and clinical characteristics. Blood samples were collected from each participant for the evaluation of SARS-CoV-2 antibodies with a lateral-flow immunochromatographic assay (LFIA). Inmates with negative results in the first serosurvey were interviewed and tested for a second time to evaluate recent symptoms history and serological status 21 days later. Samples were also retested using a chemiluminescence enzyme immunoassay (CLIA) to compare SARS-CoV-2 seroprevalence and 21-days incidence, as well as to estimate the overall infection fatality rate (IFR) and determine the diagnostic accuracy of the LFIA test.Findings: We identified 485 eligible individuals and enrolled 460 participants (94.8%), distributed across four prison units. Baseline and 21-days follow-up seroprevalence were estimated at 52.0% (95%CI 44.9-59.0) and 56.7% (95%CI 48.2-65.3) with the LFIA test; and 80.7% (95%CI 74.1-87.3) and 81.1% (95%CI 74.4-87.8) with the CLIA test, with an overall IFR of 0.02%. There were 78.2% (95%CI 66.7-89.7) symptomatic inmates among the positive cases, and the main symptoms included changes in taste or smell, headache, and fever. Sensitivity and specificity of LFIA test were estimated at 43.4% and 83.3% for IgM; 46.5% and 91.5% for IgG; and 59.1% and 77.3% for combined tests. There was a fair agreement between LFIA and CLIA results (Kappa score 0.23).Interpretation: We found rapid viral spread and high seroprevalence of anti-SARS-CoV-2 antibodies within the prison complex. The occurrence of asymptomatic infection highlights the importance of periodic mass testing in addition to case-finding of symptomatic inmates, however the field performance of LFIA tests should be validated. We recommend that vaccination strategies consider the inclusion of persons deprived of liberty and prison staff in priority groups.Funding: EN, GASR, RH, WNA acknowledge the Brazilian Ministry of Education (MEC) for support the COVID-19 response by University of Brasília (#23106.028855/2020-74). RH, WMR and WNA acknowledge the Federal District Research Foundation (FAP-DF) for grants that supported this research (# 00193-00000495/2020-72). GASR, JHC, WMR, WNA acknowledge the National Research Council (CNPq) for grants that supported this research (# 402957/2020-2)Declaration of Interest None to declare. Ethical Approval The study was part of an epidemiological investigation conducted by the Brazilian Field Epidemiology Training Program/Ministry of Health as a response to a public health emergency, and it is supported by the national law 8.080/1990. Moreover, all participants provided informed consent and ethics approval was obtained under the CONEP protocol number 37007220.1.0000.0008.