Real-world COVID-19 vaccine effectiveness in Zimbabwe: A test-negative case-control study

COVID-19 vaccination is critical in sub-Saharan Africa to reduce the disease burden. This study assessed real-world vaccine effectiveness (VE) in Zimbabwe.

To determine COVID-19 VE and factors associated with disease severity and mortality in Zimbabwe.

The study setting comprised a test-negative case-control study across health facilities in Harare and Bulawayo (May 2023 - August 2023).

Adults (≥ 18 years) were recruited from COVID-19 registers (1:1 case-control; matched by sex, age and clinic visit date). Telephone interviews assessed vaccination status, disease severity (cases) and comorbidities. Conditional logistic regression estimated VE (1 - odds ratio*100), with stratification by age and comorbidities. Ordinal and simple logistic regression analysed factors associated with disease severity and vaccination-variant relationships.

Overall vaccination coverage was 38% (fully vaccinated including boosters), with 62% unvaccinated. The median age was 38 years (interquartile range [IQR]: 30-50) with more females (n = 352). Overall VE against any COVID-19 infection was 32.2% (95% CI: 8.9, 49.5). Older age (45+ years) and chronic conditions were associated with increased hospitalisation risk. Among cases, hospitalisation rate was 34.8% (n = 174/500) and COVID-19-related mortality rate was 11.6% (n = 58/500).

This study found a moderate VE of COVID-19 vaccines in Zimbabwe, potentially influenced by age, comorbidities and variants. We highlight the need for targeted vaccination strategies and public health measures informed by these findings.

This research informs public health strategies to optimise vaccination efforts and improve health outcomes across Africa, aligning with the journal's focus on public health issues.