Repeated Leftover Serosurvey of SARS-CoV-2 IgG Antibodies in Greece, May to August 2020

Bogogiannidou, Zacharoula; Speletas, Matthaios; Vontas, Alexandros; Nikoulis, Dimitrios J.; Dadouli, Katerina; Kyritsi, Maria A.; Mouchtouri, Varvara A.; Mina, Paraskevi; Anagnostopoulos, Lemonia; Koureas, Michalis; Karavasilis, Vasileios; Nikou, Olga; Pinaka, Ourania; Thomaidis, Pavlos C.; Kadoglou, Kornilia; Bedevis, Konstantinos; Spyrou, Natalia; Eleftheriou, Alexandros A.; Papaevangelou, Vassiliki; Gikas, Achilleas; Vatopoulos, Alkiviadis; Ntzani, Evangelia E.; Prezerakos, Panagiotis; Tsiodras, Sotirios; Hadjichristodoulou, Christos

A serosurvey of IgG antibodies against SARS-CoV-2 was conducted in Greece between May and August 2020. It was designed as a cross-sectional survey and was repeated at monthly intervals. The leftover sampling methodology was used and a geographically stratified sampling plan was applied. Of 20,110 serum samples collected, 89 (0.44%) were found to be positive for anti-SARS-CoV-2 antibodies, with higher seroprevalence (0.35%) observed in May 2020. The highest seroprevalence was primarily observed in the “30–49” year age group. Females presented higher seroprevalence compared to males in May 2020 (females: 0.58% VS males: 0.10%). This difference reversed during the study period and males presented a higher proportion in August 2020 (females: 0.12% VS males: 0.58%). Differences in the rate of seropositivity between urban areas and the rest of the country were also observed during the study period. The four-month infection fatality rate (IFR) was estimated to be 0.47%, while the respective case fatality rate (CFR) was at 1.89%. Our findings confirm low seroprevalence of COVID-19 in Greece during the study period. The young adults are presented as the most affected age group. The loss of the cumulative effect of seropositivity in a proportion of previous SARS-CoV-2 infections was indicated.