In his review of the available literature, Jefferson finds a large gap between influenza vaccination policy and what the data tell us.1 What the data tell us, he writes, is that the inactivated vaccines have little or no effect on the effects measured, and the comparative evidence is insufficient to demonstrate the vaccines are safe.
Jefferson's results are consistent with previous epidemiological reviews of the effects of influenza vaccination. A 2005 US National Institutes of Health review of over 30 influenza seasons could not correlate increasing vaccination coverage after 1980 with declining mortality rates in any age group and concluded that observational studies substantially overestimate vaccination benefit.2
Annually, public health agencies in the United States and United Kingdom launch massive campaigns aimed at convincing doctors of the importance of influenza vaccination. Is this necessary? Safe and effective interventions for diseases that truly pose a threat to morbidity and mortality are unlikely to be controversial. Not only is the evidence supporting the safety and effectiveness of influenza vaccination lacking, but there are also reasons to doubt conventional estimates of the mortality burden of influenza. As I have documented previously,3 the mortality data are a mess—over the period in which the Centers for Disease Control and Prevention's statistical modelling of flu-associated mortality has estimated an 80% rise in deaths, officially recorded flu deaths have dropped by 30%. Complicating this is the fact that influenza-like illness is not only indistinguishable from influenza, but far more common, leading to unrealistic expectations of influenza vaccination.
The policy questions raised by these reviews are crucial to answer. While it is often said that influenza poses a serious burden to health, influenza vaccines impose their own particular burden—to the tune of billions of dollars annually. If policy is going to be driven by evidence, this requires us, first of all, to consider the evidence.
Competing interests: None declared.
References
- 1.Jefferson T. Influenza vaccination: policy versus evidence. BMJ 2006;333:912-5.(28 October.) [DOI] [PMC free article] [PubMed]
- 2.Simonsen L, Reichert TA, Viboud C, Blackwelder WC, Taylor RJ, Miller MA. Impact of influenza vaccination on seasonal mortality in the US elderly population. Arch Intern Med 2005;165:265-72. [DOI] [PubMed] [Google Scholar]
- 3.Doshi P. Are US flu death figures more PR than science? BMJ 2005;331:1412. [Google Scholar]