When does Follow-up on Adverse Events Improve the Understanding of Medicine and Vaccine Safety? Insights from Global Expert Perspectives.

INTRODUCTION AND

objectiveAdverse events (AEs) reported with medicines and vaccines form the foundation of pharmacovigilance (PV), enabling the detection, assessment, and prevention of drug-related risks. Initial AE reports often lack relevant clinical detail, limiting their utility. Follow-up is used to obtain additional information but is resource-intensive. Spontaneous reporting systems receive large volumes of reports and follow-up yields additional information in only a proportion of cases. Given these volumes and variable yield, it is important to define when follow-up is most likely to add value and when it is likely to be low-yield or futile. This study aimed to identify scenarios where follow-up on AEs meaningfully improves the understanding of medicine and vaccine safety, and to delineate circumstances when it may be less beneficial or futile.

methodsA Delphi based methodology was used to systematically gather expert consensus on scenarios in which follow-up of AE reports enhances the understanding of medicine and vaccine safety.

resultsData saturation was achieved after ten interviews. Panel members identified three primary scenarios in which follow-up adds value in PV: supporting causality assessment, strengthening signal detection and monitoring, and informing risk management and public health actions. They saw questionable or no value in follow up of well-characterised labelled events, cases in which the reporter cannot be contacted or did not consent to further contact, and settings where additional data were unlikely to alter benefit-risk.

conclusionThis study characterises expert perspectives on when follow-up activities are most likely to provide actionable value. Our results indicate that follow-up improves understanding when it resolves clinical uncertainty, but is inefficient when pursued without regard to impact, supporting a shift to proportionate, purpose-driven follow-up strategies for consistent and efficient use of resources including criteria for prioritisation and de-prioritisation.