Coronavirus SARS-CoV-2 antibody seroprevalence study in Estonia (two-region test study)

Background: At the end of 2019, a new coronavirus (SARS-CoV-2) was detected in China, causing coronavirus disease (COVID-19). The virus has spread rapidly around the world, including to Estonia, and in March 2020, an outbreak of COVID-19 was declared a pandemic by the World Health Organization (WHO). The disease can be severe or completely asymptomatic. Therefore, examination of patients by PCR does not allow the actual number of people exposed to SARS-CoV-2 to be estimated. To assess the actual number of people exposed to SARS-CoV-2, it is necessary to perform a population-based seroprevalence study, ie to determine the prevalence of virus-specific antibodies in the population. To our knowledge, the results of COVID-19 seroprevalence studies have not yet been published and therefore the actual prevalence of the disease is nowhere known. To assess the prevalence, we first conduct a test study in two regions of Estonia (Saaremaa and Harjumaa). The data collected from the test study are necessary to plan an adequate sample size for the nationwide SARS-CoV-2 seroprevalence study. Objectives: 1) to determine the prevalence of SARS-CoV-2 antibodies in different age groups; 2) to assess the number of people who have had COVID-19 before having a blood test; 3) to assess how many people suffered from COVID-19 asymptomatically. Methods: In the course of this cross-sectional seroprevalence study, blood sera from randomly selected people are collected in two regions of Estonia (Saaremaa and Harjumaa) and the level of SARS-CoV-2 antibodies is determined by ELISA. In addition, a short questionnaire is completed for each subject with demographic and clinical data. Importance of research results: Research is important