Zimbabwe adverse events following immunisation surveillance system: A descriptive study with COVID-19 vaccine safety updates

Abstract

Background: A functional national adverse events following immunisation (AEFI) surveillance system is vital for guiding vaccination policies and sustaining public confidence. The system helps ensure safe immunisation delivery, thereby maintaining high delivery vaccine coverage and reducing vaccine-preventable diseases (VPDs). Optimising these systems remains a critical public health priority.
Objectives: This novel study reviews and evaluates Zimbabwe’s AEFI surveillance system from 1998–2024, including updates on coronavirus disease 2019 (COVID-19) vaccine safety to identify strengths, weaknesses and opportunities for improvement.
Method: We conducted an in-depth analysis of all AEFI reports received from 1998–2024, assessing reporting trends, overall system performance AEFI investigation, causality assessment and feedback to reporters using the World Health Organization (WHO) Global Benchmarking Tool (GBT). Duplications were excluded, and reports with evidence of AEFI(s) after vaccination were included.
Results: The findings show a steady increase in AEFI reports per annum, especially from 2006–2024, with substantial increases in 2023 and 2024, reaching rates of 64 and 82 reports per 100 000 surviving infants. The reporting rate exceeded the WHO-recommended minimum AEFI reporting rate in 13 years (50%) out of the 26 years. The COVID-19 vaccination programme generated 519 AEFI reports (23%) between 2021–2023, with reporting rates of 2.1, 0.1 and 1.1 per 100 000 population, respectively.
Conclusion: A strong partnership between the immunisation programme and regulatory authority has enhanced AEFI surveillance. However, incomplete AEFI case investigations and delays in AEFIs detection remain key. System improvements should incorporate digital tools to enhance reporting investigation and signal detection, including postmortem examinations for serious AEFIs.
Contribution: The unique Zimbabwe AEFI publication contributes to the scientific knowledge, challenges and potential signals to heed to enhancing vaccine safety systems.