RESUMO
BackgroundCOVID-19 vaccines are highly effective for reducing severe disease and mortality. However, vaccine effectiveness data is limited from sub-Saharan Africa, where SARS-CoV-2 epidemiology has differed from other regions. We report COVID-19 vaccine effectiveness against progression to in-hospital mortality in Zambia. MethodsWe conducted a retrospective cohort study among admitted patients at eight COVID-19 treatment centers across Zambia during April 2021 through March 2022. Patient demographic and clinical information including vaccination status and hospitalization outcome (discharged or died) werecollected. Multivariable logistic regression was used to assess the odds of in-hospital mortality by vaccination status, adjusted for age, sex, number of comorbid conditions, disease severity, and COVID-19 treatment center. Vaccine effectiveness of [≥]1 vaccine dose was calculated from the adjusted odds ratio. ResultsAmong 1,653 patients with data on their vaccination status and hospitalization outcome, 365 (22.1%) died. Overall, 236 (14.3%) patients had received [≥]1 vaccine dose before hospital admission. For patients who had received [≥]1 vaccine dose, 22 (9.3%) died compared with 343 (24.2%) among unvaccinated patients (p <0.01). The median time since receipt of a first vaccine dose was 52.5 days (IQR: 28-107). Vaccine effectiveness for progression to in-hospital mortality among hospitalized patients was 64.8% (95% CI: 42.3-79.4%). ConclusionsAmong patients admitted to COVID-19 treatment centers in Zambia, COVID-19 vaccination was associated with lower progression to in-hospital mortality. These data are consistent with evidence from other countries demonstrating benefit of COVID-19 vaccination against severe complications. Vaccination is a critical tool for reducing the consequences of COVID-19 in Zambia. Key points- Receipt of [≥]1 COVID-19 vaccine dose reduced progression to in-hospital mortality in Zambia by 64.8% - Mortality benefit of COVID-19 vaccines was sustained during the period of omicron transmission in Zambia
