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Published on: February 16, 2022
SARS-CoV-2 Sero-Surveillance in Greece: Evolution over Time and Epidemiological Attributes during the Pre-Vaccination
Michalis Koureas1, Zacharoula Bogogiannidou1, Alexandros Vontas1
1Laboratory of Hygiene and Epidemiology, Faculty of Medicine, University of Thessaly, 41222 Larissa, Greece.
Background:
Nation-wide SARS-CoV-2 seroprevalence surveys provide valuable insights into the course of the pandemic, including information often not captured by routine surveillance of reported cases.
Methods:
A serosurvey of IgG antibodies against SARS-CoV-2 was conducted in Greece between March and December 2020. It was designed as a cross-sectional survey repeated at monthly intervals. The leftover sampling methodology was used and a geographically stratified sampling plan was applied.
Results:
Of 55,947 serum samples collected, 705 (1.26%) were found positive for anti-SARS-CoV-2 antibodies, with higher seroprevalence (9.09%) observed in December 2020. Highest seropositivity levels were observed in the "0-29" and "30-49" year age groups. Seroprevalence increased with age in the "0-29" age group. Highly populated metropolitan areas were characterized with elevated seroprevalence levels (11.92% in Attica, 12.76% in Thessaloniki) compared to the rest of the country (5.90%). The infection fatality rate (IFR) was estimated at 0.451% (95% CI: 0.382-0.549%) using aggregate data until December 2020, and the ratio of actual to reported cases was 9.59 (7.88-11.33).
Conclusions:
The evolution of seroprevalence estimates aligned with the course of the pandemic and varied widely by region and age group. Young and middle-aged adults appeared to be drivers of the pandemic during a severe epidemic wave under strict policy measures.
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