SARS-CoV-2 seroprevalence across six states of Nigeria, October 2020 and June 2021

ABSTRACT

Introduction/ Background: There have been low reported cases per population of SARS-CoV-2 in sub-Saharan Africa. Populationbased studies are needed to estimate the true cumulative incidence of SARS-CoV-2 to inform public health interventions. This study estimated SARS-CoV- 2 seroprevalence in four states in Nigeria in October 2020, and two states in June 2021. Methods: We conducted a two-stage cluster sample household survey in Enugu, Gombe, Lagos, and Nasarawa September-October 2020 and Kano and Federal Capital Territory (FCT) in June 2021. Thirty-four enumeration areas (EAs) were randomly sampled per state (30 in Lagos), and 20 households randomly selected per EA. All household members were eligible. Oral and nasopharyngeal swabs were taken for molecular testing and blood collected for antibody testing. Samples were tested on the multi-antigen target Luminex xMAP assay. Results: A total of 3,546 households (>83% of households) and 14,835 individuals (>94% of individuals) participated. In October 2020, SARS-CoV-2 seroprevalence was 25.2% (95% CI21.8-28.6) in Enugu, 9.3% (95% CI7.0- 11.5) in Gombe, 23.3% (95% CI20.5, 26.4) in Lagos, and 18.0% (95% CI14.4-21.6) in Nasarawa. In June 2021, seroprevalence was 42.6% (95% CI39.4-45.8) in Kano and 40.3% (95% CI34.7-45.9) in FCT. By July 2021, <3% of the populations of Kano and FCT had received at least one vaccine dose. Among the 38.9% and 53.1% respectively who indicated they would not take the vaccine, safety concern was the main reason (84.9%, 83.7% respectively). Impact Population based surveys are important tools to estimate the true seroprevalence of novel pathogens more accurately with predominantly asymptomatic presentation. These surveys provide seroprevalence provide estimates that are not subject to bias from unequal distribution or uptake of testing services during outbreaks for development of accurate public health mitigation measures. Conclusion: Sixteen months in, approximately 60% of the populations of FCT and Kano had no antibodies to SARS-CoV-2, indicating a significant proportion of the population remained vulnerable to infection. Rapid scale-up of vaccine distribution and efforts to encourage vaccine uptake are needed to prevent the emergence of SARS-CoV-2 variants of concern.