Factors associated with SARS-CoV-2 infection amongst Health Workers in Bamako, Mali: a cohort study from November 2021 to February 2023

Background . Health workers (HWs) are at high risk of SARS-CoV-2 infection due to their frontline role and considered as priority group for COVID-19 vaccination. This study aimed to estimate SARS-CoV-2 infection and COVID-19 incidence rates and identify the risk factors among HWs in Mali to strengthen prevention measures. Method . A cohort study of 1098 HWs was conducted from November 2021 to February 2023, in six health centers and two university hospitals of Bamako. Sociodemographic and clinical data, nasopharyngeal swabs were collected to determine asymptomatic SARS-CoV-2 infection rate during the cross-sectional surveys. Self-reported COVID-19 cases were collected during biweekly follow-ups. REDCap was used for data management. Mixed-effects Cox regression models and multivariate logistic regression were used to identify the risk factors for SARS-CoV-2 infection. Results. Amongst 1098 HWs, 34.7% were nurses, 8.2% have had contact with COVID-19 patients, and 18% with COVID-19 samples. A significant change in the rate of SARS-CoV-2 infection (asymptomatic infection) was observed between November 2021 (3.4%), February 2022 (1.3%) and February 2023 (4.8%, p = 0.0001). SARS-CoV-2 21I (36.7%) and 21L (8.2%) Delta variants were observed mainly in November 2021 giving place to Omicron over time. The distribution of SARS-CoV-2 variants was similar in vaccinated and unvaccinated health workers (p = 0.716). Absence of anti-N antibodies (HR=3.98 95%CI, 2.23-7.12), contact with COVID-19 patients (HR=3.85 95%CI, 2.00-7.44]), use of public transport (HR=2.20 95%CI, 1.05-4.61) and participation in public events (HR=7.93 95%CI, 1.03-60.1) were associated with a higher risk COVID-19 confirmed cases (symptomatic SARS-CoV-2 infection). Conclusion. Results show a high rate of SARS-CoV-2 infection in February 2023, and the risk factors were both in work and community settings.