Abstract
Objectives: To assess the prevalence of SARS-CoV-2-specific IgM and IgG antibodies among workers of the three public higher education institutions of Porto, Portugal, up to July 2020.
Methods: A rapid point-of-care test for specific IgM and IgG antibodies of SARS-CoV-2 was offered to all workers (SD Biosensor STANDARD Q COVID-19 IgM/IgG Duo and STANDARD Q COVID-19 IgM/IgG Combo). Testing was performed and a questionnaire was completed by 4592 workers on a voluntary basis from 21 May to 31 July 2020. We computed the apparent IgM, IgG, and combined IgM or IgG prevalence, along with the true prevalence and 95% credible intervals (95% CrI) using Bayesian inference.
Results: We found an apparent prevalence of 3.1% for IgM, 1.0% for IgG and 3.9% for either. The estimated true prevalence was 2.0% (95% CrI 0.1% to 4.3%) for IgM, 0.6% (95% CrI 0.0% to 1.3%) for IgG, and 2.5% (95% CrI 0.1% to 5.3%) for IgM or IgG. A SARS-CoV-2 molecular diagnosis was reported by 21 (0.5%) workers; and of these, 90.5% had a reactive IgG result. Seroprevalence was higher among those reporting contacts with confirmed cases, having been quarantined, having a previous molecular negative test or having had symptoms.
Conclusions: The seroprevalence among workers from the three public higher education institutions of Porto after the first wave of the SARS-CoV-2 infection was similar to national estimates for the same age working population. However, the estimated true seroprevalence was approximately five times higher than the reported SARS-CoV-2 infection based on a molecular test.
Keywords: COVID-19; Epidemiology; Occupational Health; Public Health Surveillance.
【저자키워드】 COVID-19, Epidemiology, occupational health, public health surveillance, 【초록키워드】 SARS-CoV-2, IgG, IgM, antibody, SARS-COV-2 infection, Seroprevalence, Infection, Symptoms, Prevalence, point-of-care, Testing, IgG antibody, Molecular diagnosis, IgM/IgG, Bayesian inference, age, molecular, estimate, Portugal, First wave, questionnaire, occupational, Contact, IgM and IgG, confirmed cases, National, Porto, specific IgM, molecular test, SD Biosensor, negative test, Public, FIVE, reactive, reported, was performed, interval, CrI, offered, the SARS-CoV-2, 【제목키워드】 cross-sectional, SARS-CoV-2 antibody, Porto,