Seroprevalence of anti SARS-CoV-2 antibodies in a random sample of inhabitants of Katowice Region, Poland

Abstract

Unknown seroprevalence of COVID-19 in Poland was the reason for implementation of a seroepidemiological study in the Katowice Region (2 100 000 inhabitants). In October-November 2020 questionnaire examination and measurement of anti-SARSCOV-2 IgG and IgM antibodies (Euroimmun ELISA) were performed in a random sample of general population, stratified for age and sex (n = 1167). The objectives of the study were to estimate the prevalence of SARS-CoV-2 antibodies and to assess their host-related correlates. The prevalence of IgG seropositivity was 11.4% (95%CI: 9.5 – 13.2%) and of IgM seropositivity was 4.6% (95%CI: 3.5 – 5.8%). Diagnosis of COVID-19 was found in 4.8% of subjects, 12.7% had contact with a COVID-19 patient, and 12.2% were put on quarantine, prior to the study. Positive IgG test was statistically significantly associated with age (inverse relationship), person’s contact with COVID-19 patient, quarantine, and two symptoms in the past: fever and loss of smell/taste. Positive IgG tests were less prevalent in subjects who had diagnoses of arterial hypertension, diabetes or rheumatologic disorders. For positive IgM test quarantine and loss of smell/taste were the only explanatory variables, and no effect of chronic diseases was found. In Poland, in the period October-November 2020, the prevalence of SARS-CoV-2 infection was larger than earlier estimates obtained in other European countries, probably reflecting the ascending curve of the „second wave” of epidemic. Such conclusion seems to be supported by associations of anti-SARS-CoV-2 antibodies with a history of contacts with COVID-19 patients and symptoms suggestive of COVID-19.