The evidence relating to the use of influenza vaccines in people over the age of 65 is poor, despite the fact that vaccination has been recommended for the prevention of flu in older people for the last four decades, scientists have said.
Adults aged 65 and over are considered one of the most vulnerable groups during flu season. As such, they are a priority for vaccination programmes. However, very few systematic reviews of the effectiveness of vaccines in this group have ever been carried out.
Cochrane researchers in Italy conducted a thorough search of studies based on previous vaccine trials. Randomised controlled trials (RCTs) are often considered the ‘gold standard’ of trials, 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.
According to the team, 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. But until we have all available evidence, it is hard to reach any clear conclusions about the effectiveness of influenza vaccines in older people," said lead researcher, Tom Jefferson of the Cochrane Collaboration in Rome.
He said that 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. 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,” he added.
Details of these findings are published in the Cochrane Database of Systematic Reviews 2010.
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