Widespread SARS-CoV-2 exposure in West Africa: findings from a 20,748-participant multi-country seroepidemiology study

Background Africa seemed to have had low SARS-CoV-2 infection and COVID-19 morbidity and mortality. While several studies reported high SARS-CoV-2 seropositivity among healthy Africans, others hypothesized that this could have resulted from pre-existing cross-reactive antibodies. Our study tracks trends in seropositivity across three West African countries during the Delta- and Omicron-dominant pandemic periods using validated SARS-CoV-2 IgG/IgM rapid diagnostic tests (Prestige Diagnostics in Ghana and Burkina Faso; SD Biosensor in Nigeria). Methods Cross-sectional studies were conducted in three West African countries (Burkina Faso, Ghana, and Nigeria), with study sites conveniently selected within each country. Using validated immunoassay kits with published validation procedures, SARS-CoV-2 antibodies were detected in peripheral blood during the Delta- and Omicron-dominant periods. Because we did not perform widespread viral sequencing on participant samples, we could not attribute seropositivity to a specific variant; instead, we classified sampling periods by the variant reported as dominant nationally/globally at the time of sample collection. Participants’ demographic and clinical data were obtained using a semi-structured questionnaire, and the primary outcome was the proportion of each population with SARS-CoV-2 antibodies. Results Across the 3 countries, 20,748 participants were recruited, and SARS-CoV-2 IgG seropositivity ranged from 24.1 to 76.4%, with higher rates during the Omicron-dominant period. All sites showed low self-reported vaccination rates, suggesting that seropositivity may be primarily driven by natural infection rather than vaccination. While there was a significant positive association between seropositivity and age across all sites, the association with other demographic factors was country-dependent, and most participants expressed positive opinions of vaccination. Conclusion This is one of the largest multi-country community-based SARS-CoV-2 seroepidemiology studies in Africa, showing widespread exposure to SARS-CoV-2 infection among our study population across three West African countries. These findings are consistent with a marked disconnect between high population exposure and low reported clinical burden, underscoring the need for strengthened community surveillance.