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.