Seroprevalence and Determinants of SARS-Cov-2 Antibodies Among Healthcare Workers in Dar es Salaam, Tanzania
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Background
Studies from the Sub-Saharan African (SSA) countries suggest an underestimate of SARS-CoV-2 infections early in the pandemic. To understand and inform infection control strategies to protect key and vulnerable populations, this study investigated the seroprevalence and factors associated with anti-SARS CoV-2 seropositivity among healthcare workers (HCWs) in Dar es Salaam, Tanzania.
Methods
This cross-sectional study was conducted in three tertiary and national hospitals in Dar es Salaam, Tanzania. Employed HCWs aged ≥18 years were enrolled between October 2021 and March 2022. Laboratory testing for Immunoglobulin G (IgG) against SARS-CoV-2 nucleocapsid (N) or spike (S) proteins was performed using WHO/FDA pre-qualified SARS-CoV-2 ELISA test kits, and data were collected on demographics and COVID-19-related exposures. Descriptive statistics were used to determine the SARS-CoV-2 antibody prevalence. Multivariable Modified Poisson regression with robust standard errors accounting for clustering within sites was used to test the independent association between HCW characteristics and SARS-CoV-2 serologic status.
Results
A total of 402 participants [mean age (SD) of 37.9 (9.7) years] were included in this study. 150 (37.3%) reported receiving at least one dose of SARS-CoV-2 vaccine. The overall seroprevalence of anti-SARS-CoV-2 antibodies (anti-SARS-CoV-2 IgG (S or N)) was 90.9% (358/394) among those with valid results. HCWs who reported receiving the SARS-CoV-2 vaccine were 1.14 times more likely to have anti-SARS-CoV-2 antibodies compared to those who reported not being vaccinated (aPR (95% CI) = 1.14 (1.03- 1.26)). HCWs who believed to have contracted COVID-19 previously but never tested had an 11% higher risk of being seropositive for SARS-CoV-2 IgG compared to those who thought never to have contracted COVID-19 before (aPR (95% CI) = 1.11 (1.05- 1.16)). Anesthetists and HCWs working in the laboratory and Obstetrics and Gynecology departments were more likely to have SARS-CoV-2 antibodies than HCWs from the Emergency Medicine Department (EMD).
Conclusion
The seroprevalence of anti-SARS-CoV-2 IgG among HCWs in this study was high in this population indicating high SARS-CoV-2 exposure among HCWs. Our work highlights the need for more effective infection control practices in healthcare settings in future pandemics like these, especially among HCWs at highest risk.
