Descriptive Study of the Adverse Events Following Immunization (AEFIs) Surveillance System in Zimbabwe

Abstract

Abstract Introduction: Functional national systems that monitor Adverse Events Following Immunization (AEFIs) are vital for implementing evidence-based vaccination policy while ensuring the safe access to these life-saving technologies. These systems can counteract vaccine hesitancy by increasing public trust and uptake in vaccination minimizing the burden of vaccine-preventable diseases (VPDs). Ensuring that these systems function optimally is a critical public health imperative. This is a novel study evaluating AEFI surveillance system including causality assessment, in Zimbabwe. Aim:This study provides a review of Zimbabwe’s national AEFI surveillance system since its launch in 1998, highlighting strengths, weaknesses, and opportunities for improvement. Method: We conducted an in-depth analysis of all AEFI reports received until 2021, assessing reporting trends and overall performance of the AEFI system in terms of investigation, causality assessment. The WHO Global Benchmarking Tool (GBT) was used to assess regulatory performance in terms of AEFI surveillance. Duplications were excluded and reports with evidence of AEFI(s) after vaccination were included. Results: There was a steady increase of AEFI reports per annum particularly from 2006 to 2021 with a more dramatic increase during the COVID-19 epidemic with an AEFI reporting ratio of 43.46/million adults for COVID-19 vaccinations in 2021. The reporting ratio exceeded the WHO recommended minimum AEFI reporting ratio of 10 per 100000 surviving infants during eleven years (47.84%) out of the twenty-three years since inception of the surveillance. The GBT assessment demonstrated that the AEFI surveillance system evolved for all manufacturers or license holders. Conclusion: Close partnership between the immunization program and regulatory authority has enhanced AEFI surveillance in Zimbabwe. Incomplete AEFI case investigations for and timely AEFI detection are challenges that need to be addressed. System strengthening should include consideration of digital innovations to improve detection, optimizing case investigation of serious AEFI including post-mortems and utilizing VigiPoint disproportionate analysis for signal detection.