SARS-CoV-2 antibody seroprevalence in Tbilisi, the capital city of country of Georgia

Background: Georgia timely implemented effective response measures, with testing, contact tracing and isolation being the main pillar of the national response, achieving the lowest cumulative incidence of SARS-CoV-2 in the European region. Methods: We conducted a survey to estimate SARS-CoV-2 IgG antibody seroprevalence among adult residents of capital city of Tbilisi (adult population: 859,328). Participants were recruited through respondent driven sampling during May 18-27, 2020. Blood specimens were tested for SARS-CoV-2 IgG antibodies using commercially available lateral flow immunoassay (COVID-19 IgG/IgM Rapid Test Cassette, Zhejiang Orient Gene Biotech). Crude seroprevalence was weighted by population characteristics (age, sex, district of Tbilisi) and further adjusted for test accuracy. Results: Among 1,068 adults recruited 963 (90.2%) were between 18 and 64 years-old, 682 (63.9%) women. 176 (16.5%) reported symptoms indicative of SARS-CoV-2 infection occurring in previous three months. Nine persons tested positive for IgG: crude seroprevalence: 0.84%, (95% CI: 0.33%-1.59%), weighted seroprevalence: 0.94% (95% CI: 0.37%-1.95%), weighted and adjusted for test accuracy: 1.02% (95% CI: 0.38%-2.18%). The seroprevalence estimates translate into 7,200 to 8,800 infections among adult residents of Tbilisi, which is at least 20 times higher than the number of confirmed cases. Conclusions: Low seroprevalence confirms that Georgia successfully contained spread of SARS-CoV-2 during the first wave of pandemic. Findings also suggest that undocumented cases due to asymptomatic or very mild disease account for majority of infections. Given that asymptomatic persons can potentially spread the virus, test and isolate approach should be further expanded to control the epidemic.