Seroprevalence against SARS-CoV-2 among blood donors in Niamey, Niger, from October 2021 to March 2022

Abstract During the first wave of the COVID-19 pandemic, a substantial proportion of SARS-CoV-2 infections were asymptomatic or mild and therefore likely to remain undetected by routine clinical surveillance. Blood donor serosurveys provided an important complementary approach for estimating community exposure and identifying infections that may not have been captured through symptom-based testing. In this context, this study aimed to estimate SARS-CoV-2 seroprevalence and identify factors associated with seropositivity among blood donors attending the Centre National de Transfusion Sanguine (CNTS) in Niamey, Niger. A cross-sectional study was conducted from October 2021 to March 2022 among blood donors attending the Centre National de Transfusion Sanguine (CNTS) in Niamey, Niger. Participants were selected using systematic random sampling (sampling interval, k = 6), and 3,656 blood donors were included. Data on socio-demographic characteristics, SARS-CoV-2 exposure, and preventive practices were collected using a structured questionnaire, and blood samples were tested for SARS-CoV-2 antibodies. Chi-square and Fisher’s exact tests were used to assess associations between categorical variables. Among the 3656 selected blood donors, sex ratio (M/F) was 4.1 and 12% were vaccinated with at least one dose. The overall seroprevalence of SARS-CoV-2 among vaccinated and non-vaccinated was respectively 65% and 53% (p-value < 0.01). In vaccinated group, seropositivity rate was statistically higher in more 50 years age group (87%,) and no difference was shown in non-vaccinated group (p-value = 0.54). Among vaccinated, according with blood groups, 0 negative group was less positive than other groups (46%) and among unvaccinated group 0 + group was less positive than other groups (48%)). In multivariate analysis, headache and anorexia were associated to SARS-CoV-2 seropositivity. Blood donor seroprevalence studies provide a rapid, scalable, and ethically deployable surveillance necessary to track a respiratory virus with high asymptomatic carriage, make the control of virus circulation possible in healthy people and help implement strategies to reduce virus transmission.