Seroprevalence of SARS-CoV-2 antibodies in blood donors during the third wave of infection in Campeche Mexico.

At the end of 2020 and previous to the second wave of COVID-19 in Mexico, the seroprevalence in unvaccinated people in the state of Campeche, Mexico was below 15 %. The prevalence changes with ongoing pandemic and per geographical areas. Blood donors screening is a powerful and cost-effective alternative to monitor the population's infection exposure. The aim of the study was to estimate IgG anti-SARS-CoV-2 seropositivity in the Campeche's main blood bank in Mexico. This was a cross-sectional study carried out at the main blood bank of the State of Campeche, located in the Yucatan peninsula, Mexico for the period of August through September 2021 during the third wave of the epidemic. A blood sample from 479 blood donors were included in the study, the overall seropositivity for SARS-CoV-2 IgG antibodies was 69.1 %. Vaccinated donors represented 69.9 % versus 29.4 % unvaccinated. The seropositivity in unvaccinated represented 42.5 % and 81.17 % in vaccinated. The seroconversion in vaccinated donors after first shot was 79 % for Astra-Zeneca-vaccine and 90 % for Pfizer-vaccine. In conclusion 69.1 % of blood donors are seropositive for SARS-CoV-2 and 42.5 percent unvaccinated people are already also seropositive.