preprint · medRxiv
A cross-sectional study carried out across three tertiary and national hospitals in Dar es Salaam, Tanzania, assessed the presence of SARS-CoV-2 antibodies among healthcare workers between October 2021 and March 2022. Using pre-qualified ELISA test kits targeting nucleocapsid or spike proteins, the investigation analysed blood samples and survey data from 402 hospital staff. The overall antibody prevalence reached 90.9 percent among those with valid test results, reflecting substantial prior exposure to the virus. Although just over a third of participants had received at least one vaccine dose, vaccination was linked to a higher likelihood of antibody presence. Seropositivity was also notably higher among staff who suspected prior untested infection, as well as personnel working in anaesthetics, laboratory medicine, and obstetrics and gynaecology when compared to emergency department colleagues.
Understanding actual infection rates helps reveal how widely a virus spreads in high-risk environments where official case numbers may be underestimated. Highlighting vulnerability among frontline hospital staff helps health authorities design better infection prevention protocols, protect essential workers, and direct targeted occupational safety measures during future respiratory disease outbreaks.
The abstract does not indicate an application pathway, as it focuses strictly on epidemiological surveillance and clinical infection control insights.
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Abstract 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.
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DOI: 10.1101/2025.02.12.25322138
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