SARS-CoV-2 seroprevalence in Kaduna State, Nigeria during October/November 2021, following three waves of infection and immediately prior to detection of the Omicron variant

Nigeria is the most populated country in Africa with an estimated ~213 million inhabitants. As of November 2021 there have been three waves of SARS-CoV-2 infection in Nigeria but there has been only one seroprevalence survey conducted to assess the proportion of a population that have been infected, which was performed in December 2020 after the first wave of infection. To provide an update on seroprevalence in Nigeria, we conducted survey at one urban site (n=400) and one rural site (n=402) in Kaduna State, Nigeria during October and November 2021 following the third wave of infection. Seroprevalence for the urban and rural sites was 42.5% and 53.5% respectively (mean 48.0%). Symptoms associated with seropositivity were identified for each site. The overall seroprevalence among unvaccinated individuals was 45.4%. The data indicates an infection rate in Kaduna State at least 387 times greater than that derived from cases confirmed by PCR. Extrapolating to the whole of Nigeria, it would suggest there has been at least 96.7 million infections (compared to 206,138 confirmed cases at the time of surveillance). The work presented here will inform public health policy and deployment strategies for testing, treatment, and vaccination in Nigeria, and provide a baseline for SARS-CoV-2 seroprevalence in Nigeria immediately prior to the spread of the Omicron variant.