SARS-CoV-2 antibody seroprevalence in Togo: a national cross-sectional household survey, May-June, 2021.

Background: The extent of SARS-CoV-2 circulation in African countries is still unclear. Seroprevalence studies are a common approach to epidemiological surveillance, allowing estimation of the proportion of people who have had contact with the virus. We aimed at estimating the seroprevalence of anti-SARS-CoV-2 antibodies and associated factors in Togo at the national level in 2021 according to age groups, gender, and place of residence (rural or urban).

Methods: From 15 May to 31 June 2021, we conducted a nationally representative cross-sectional serological survey in 12 health districts (two districts per health region) in the > 5 years old population in Togo. The Wantai SARS-CoV-2 total antibody assay S protein receptor-binding domain-based ELISA (Wantai Biological Pharmacy Enterprise Co.; Beijing, China) was used to determine the presence of SARS-CoV-2 total antibodies in plasma. Crude and weighted seroprevalences (weighted by age, sex and place of residence) were calculated and then weighted seroprevalences were adjusted according to sensitivity and specificity of the ELISA test. Finally, logistic regression models were performed in order to describe factors associated.

Results: Of the 7593 participants, the overall weighted and adjusted seroprevalence of total anti-SARS-CoV-2 antibodies was 65.5% (CI95%: 18.9-21.1). Urban dwellers, young adults (30-49 years) and vaccinated individuals were significantly more likely to be seropositive.

Conclusion: The high seroprevalence we observed is consistent with observations across West Africa. Quantification of the level of immunity in the population is needed to know how close we are to herd immunity. In the meantime, vaccination against the COVID-19 remains necessary.