According to the findings of a study of over 3,500 patients aged 65 or more, the flu vaccine might not be able to protect the elderly from pneumonia as once thought.

The study, carried out by a team of researchers led by Michael L. Jackson of the Group Health Center for Health Studies in Seattle, analyzed data from seniors who had already developed pneumonia, with the purpose of finding the effectiveness of the flu vaccine. Published in The Lancet, it used an accurate case control method that included a control time period, after a flu vaccine became available but before each flu season really began.

Other studies have been made before, but they failed to give an explanation for the discrepancies between healthier senior citizens and those who were “frail,” affirmed M. Jackson. Throughout the pre-flu season periods, the vaccinated people proved to be much less likely to get pneumonia.

One justification could be the “healthy user” effect. Jackson explains: "Those who got the vaccine happened to be healthier - not because the flu vaccine was protecting them from pneumonia caused by the flu, since it wasn't present yet.”

However, the disappointing results didn’t discourage researchers or stopped them from insisting that the flu vaccine still has beneficial effects, increasing the immunity to pneumonia over time, blocking transmission of it.

All things considered, flu vaccines indeed reduce the number of flu-related deaths, but their effects have been overestimated, the flu shots apparently being less helpful than previously believed.