Influenza Vaccines: Poor Evidence for Effectiveness in Elderly

Despite the fact that vaccination has been recommended for older people to prevent influenza, the evidence for the safety and efficacy of flu vaccines for people aged over 65 is poor.

Adults aged 65 and over are some of the most vulnerable during influenza season and a priority for vaccination programs, but very few systematic reviews of the effectiveness of vaccines for this group have ever been carried out.

Researchers conducted a thorough search of studies based on previous vaccine trials. Randomised controlled trials (RCTs) are often considered the “gold standard”, but of the 75 studies included in their review, the researchers were only able to identify one recent RCT with “real” outcomes. In other words, this was the only RCT that used influenza cases as an outcome, as opposed to surrogate outcomes such as measurements of influenza antibodies in the blood. All the other studies included in the review were deemed of low quality and open to bias.

The limited reliable evidence from the studies suggests that the effectiveness of influenza vaccines is modest at best. “Our estimates are consistently below those usually quoted by economists and in decision making,” said lead researcher Tom Jefferson of the Cochrane Collaboration in Rome, Italy. “But until we have all available evidence, it is hard to reach any clear conclusions about the effectiveness of influenza vaccines in older people.”

“As the evidence is so scarce at the moment, we should be looking at other strategies to complement vaccinations. Some of these are very simple things like personal hygiene, and adequate food and water,” says Jefferson. “Meanwhile, we need to undertake a high-quality, publicly-funded trial that runs over several seasons to try to resolve some of the uncertainties we’re currently facing.”

Jefferson is also one of the authors of a second review published recently that focuses on the efficacy of influenza vaccinations in for health care personnel who work with the elderly, again the results of which are inconclusive. Each of the four trials included in the review were of inadequate quality and reached implausible conclusions. The researchers were unable to draw any conclusions about whether vaccinating health care workers helps to prevent influenza symptoms and death in people aged over 60.

Copies of both reviews are available though the Cochrane Library website. HealthInsite also has a topic page on Influenza Vaccine.

Created 12 March 2010.