Side Effects of Influenza Vaccination in Healthy Older People: A Randomised Single-Blind Placebo-Controlled Trial

Abstract

Objectives: To investigate the frequency of side effects following influenza vaccination in healthy participants aged 65–74 years. Materials and Methods: A single-blind randomised placebo-controlled trial was performed in general practices in central Liverpool on 729 healthy individuals (341 females and 388 males) aged 65–74 (median age 68.9) years, of whom 552 received influenza vaccine and 177 received placebo. The main outcome measures were analysed from adverse reactions reported by the subjects on a postal questionnaire 3 days after vaccination. Results: 724 (99.3%) questionnaires were returned. 62 (11.3%) participants who received influenza vaccination complained of local symptoms compared with 9 (5.1%) participants who received placebo (difference 6.2%; 95% CI 1.3 to 10.0%; p = 0.02). 192 (35.1%) individuals who received influenza vaccine complained of one or more systemic side effects compared with 75 (42.4%) who received placebo (difference –7.3%; 95% CI –15.6 to 0.9%; p = 0.10). Conclusion: Healthy people belonging to this age group can be reassured that, when compared with placebo, influenza vaccination causes few, if any, systemic side effects and only a low incidence of local side effects.