Interest of seroprevalence surveys for the epidemiological surveillance of the SARS-CoV-2 pandemic in African populations: insights from the ARIACOV Project in Benin

Background Many SARS-CoV-2 seroprevalence surveys since the end of 2020 have disqualified the first misconception that Africa had been spared by the pandemic. Through the analysis of three SARS-CoV-2 seroprevalence surveys carried out in Benin as part of the ARIACOV project, we argue that the integration of epidemiological serosurveillance of the SARS-COV2 infection in the national surveillance package would be of great use to refine the understanding of the COVID-19 pandemic in Africa. Methods Three repeated cross-sectional surveys have been carried out in Benin, two in Cotonou, the economic capital in March and May 2021, and one in Natitingou, a semi-rural city in North in August 2021. The global and by age-groups weighted seroprevalences have been estimated and the risk factors of the infection by SARS-COV-2 have been assessed by using logistic regression. Results In Cotonou, a slight increase in overall age-standardized SARS-CoV-2 seroprevalence from 29.77% (95% CI: 23.12-37.41%) at the first survey to 34.86% (95% CI: 31.57-38.30%) at the second survey was observed. In Natitingou the global adjusted seroprevalence was 33.34% (95% CI: 27.75-39.44%), much higher than expected. Adults over 40 seemed to be more at risk than the youngest during the first survey in Cotonou but no longer in the second survey, showing the persistence of the SARS-COV-2 virus circulation outside the epidemic waves. Conclusions A routine serological surveillance on strategic sentinel sites and / or populations could constitute a cost / effective compromise to better anticipate the onset of new waves and define public health strategies.