ABSTRACT
In the Czech Republic, the first wave of the COVID-19 epidemic, caused by the SARS-CoV-2 virus, occurred in the spring of 2020, peaking at the end of March. From March 1st to May 31st, a total of 9,230 people tested positive by PCR were detected. We assessed the prevalence of COVID-19 infections in employees of the National Institute of Public Health at the end of the first wave by detecting specific antibodies against SARS-CoV-2. Voluntary testing for the presence of IgA and IgG antibodies was performed by ELISA tests using Euroimmun SARS-CoV-2 IgA and Euroimmun SARS-CoV-2 IgG semi-quantitative commercial assays. The participants answered a questionnaire regarding symptoms of an acute respiratory infection in the last quarter and known contact with COVID-19 infection. A total of 78 out of 270 persons (29%) experienced symptoms of acute respiratory infection, 7 (2.6%) lost the olfactory sense or taste and 15 (5.6%) were in contact with an infected person. The first sampling was performed between April 6th and May 22nd, 2020. A total of 270 employees were tested, of which 224 (83%) were women. The IgA and IgG antibodies SARS-CoV-2 were positive or borderline in 31 subjects. The second sample was taken from 30 of them and the third sample was from taken two persons several weeks apart. Based on the dynamics of the antibodies, 10 (3.7% of the whole group) were evaluated as seropositive, in whom we indirectly infer a past SARS-CoV-2 infection. A total of 246 people had negative serology (of which 239 based on the first sample and 7 based on the second one). In 14 people it was not possible to determine whether an infection occurred, i.e. the result was evaluated as inconclusive. The positive association of persistent seroconversion in the symptomatic subjects compared to the asymptomatic ones was statistically insignificant with a relative risk of 1.61 (95% CI: 0.47–5.54), p = 0.449. © 2021, Czech Medical Association J.E. Purkyne. All rights reserved.