Skip navigation
Link to Back issues listing | Back Issue Listing with content Index | Subject Index

Influenza vaccine in over-65s

Systematic review
Results
Comment

Influenza vaccination time is coming round again. Many of the arguments have been won, and many older people living at home now have their annual jab. Not all do, and not everyone is convinced. In Bandolier 11 we examined a randomised trial of influenza vaccination in Holland, and in Bandolier 73 a review on people younger than 65 years. Both were persuasive. A new systematic review extends the evidence base [1].

Systematic review


In that wonderful city of Melbourne, the authors used an extensive search strategy for studies in any language where inactivated influenza vaccine was used, the study period was determined by influenza surveillance, and the population was community-based elders of 65 years or more. Excluded were studies on institutionalised persons, where comparability of study groups was not reported, studies with a cross-sectional design and those where influenza strains used did not match circulating strains, or where this was not reported.

The outcome used was vaccine effectiveness. Vaccine effectiveness (VE) is given by the equation:

VE = (1 - relative risk) x 100

Thus a relative risk of 0.5 in an outcome gives a vaccine effectiveness of 50%, or a 50% reduction in the rate of that outcome over control.

Results


There were 15 studies. One was a randomised trial ( Bandolier 11 ), two others were labelled as clinical trials, and the remainder were case-control or cohort studies. Results of vaccine effectiveness for different outcomes are shown in Figure 1. The biggest effect was on mortality.

Figure 1: Vaccine effectiveness of influenza vaccine in the over 65s measured by different outcomes



Comment


This confirms the effectiveness of influenza vaccines for a variety of outcomes. The results confirm other meta-analyses from healthy adults or institutionalised elderly. So why bother doing the study? The answers to this are several, but the main importance to us is likely to be a reaffirmation that something done every year is worth doing, and worth doing well.

References:

  1. T Vu et al. A meta-analysis of effectiveness of influenza vaccine in persons aged 65 years and over living in the community. Vaccine 2002 20: 1831-1836.
previous story in this issue