The Impact of Influenza Vaccination on Antibiotic Prescribing in Older Adults: A Self-Controlled Case Series Analysis

BackgroundInfluenza-like illness is a key driver of antibiotic prescribing, contributing to unnecessary antibiotic use and antimicrobial resistance. Influenza vaccination may reduce antibiotic prescribing; however, robust evidence remains limited. To address this, we examined the association between influenza vaccination and antibiotic prescribing in individuals aged 65 and older in England, using a self-controlled case series (SCCS) approach. MethodsWe conducted a SCCS analysis using electronic primary care health records from the Clinical Practice Research Datalink, covering eight influenza seasons (2011-2019). Eligible individuals had at least one influenza season in which they were both vaccinated and unvaccinated. The primary outcome was days prescribed antibiotics, focusing on respiratory tract infection (RTI)-linked prescribing. To account for seasonal variation in influenza circulation, we examined antibiotic prescribing from September-April and further restricted the analysis to January-April during peak influenza activity. Incidence rate ratios (IRRs) were estimated using conditional Poisson regression, adjusting for comorbidities, healthcare interactions, and other vaccinations. FindingsThe analysed extract included 268,352 individuals, of whom 48,329 met the inclusion criteria. On average, individuals were prescribed antibiotics for 8 days per influenza season. Findings suggest influenza vaccination may reduce overall and RTI-related antibiotic prescribing, particularly during peak influenza season. The IRR for RTI-linked prescribing decreased from 0{middle dot}96 (95% CI: 0{middle dot}95-0{middle dot}98) for September-April to 0{middle dot}91 (95% CI: 0{middle dot}89-0{middle dot}93) for January-April. InterpretationInfluenza vaccination contributes to reduced RTI-related antibiotic prescribing in older adults during the influenza season. Advocating for increased uptake and use of immunisation against respiratory pathogens in older populations.