Our aim was to assess the seroprevalence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection after the lockdown in a sample of the Corsican population Between 16 April and 15 June 2020, 2312 residual sera were collected from patients with a blood analysis conducted in one of the participating laboratories Residual sera obtained from persons of all ages were tested for the presence of anti-SARS-CoV-2 Immunoglobulin G (IgG) using the EUROIMMUN enzyme immunoassay kit for semiquantitative detection of IgG antibodies against the S1 domain of viral spike protein (ELISA-S) Borderline and positive samples in ELISA-S were also tested with an in-house virus neutralization test (VNT) Prevalence values were adjusted for sex and age A total of 1973 residual sera samples were included in the study The overall seroprevalence based on ELISA-S was 5 27% (95% confidence interval (CI), 4 33&ndash;6 35) and 5 46% (4 51&ndash;6 57) after adjustment Sex was not associated with IgG detection However, significant differences were observed between age groups (p-value = 1 E-5) The highest values were observed among 10&ndash;19, 30&ndash;39, and 40&ndash;49 year-old age groups, ranging around 8&ndash;10% The prevalence of neutralizing antibody titers &ge;40 was 3% (2 28&ndash;3 84) In conclusion, the present study showed a low seroprevalence for COVID-19 in Corsica, a finding that is in accordance with values reported for other French regions in which the impact of the pandemic was low
Seroprevalence of SARS-CoV-2 IgG Antibodies in Corsica (France), April and June 2020