The article is very interesting and necessary. It evaluates globally the efficacy of influenza vaccines over a large period and with many patients included.

The results are consistent and the importance of the article is that many studies have been reviewed, so the sample size is very large. It opens the way for further basic studies to understand why for some strains the protection is higher (e.g. H1N1) than for other strains (H3N2), indicating that we are far from a universal flu vaccine yet. The fact that the influenza virus changes so much makes it difficult to make vaccines that cover well the exact strain that is circulating.

[As for limitations] The authors themselves already indicate limitations in their study. It would be interesting if the article had included the strains circulating annually with the vaccine that was designed in those particular years, which can greatly influence the protection obtained. In addition, more age-specific subgroups of analysis could have been done.

The final message that should get through to the public is that influenza vaccination is effective against the dangerous strains: it prevents death and serious illness. It does so best against two of the three strains tested. As its effectiveness decreases over time, it is important to revaccinate at-risk groups, especially young children and the elderly, every year. Influenza vaccination saves lives and this study proves it.

Studies such as this one reinforce the evidence for the importance of continuing to promote influenza vaccination campaigns year after year. Meta-analyses of this magnitude reinforce the message that vaccines are safe, and not only reduce the transmission of influenza but, more importantly, significantly reduce the risk of serious complications in those who - even if vaccinated - end up becoming infected, as well as the mortality associated with this highly prevalent infection.

The paper analyses the effectiveness of influenza vaccines, demonstrating that, although their ability to prevent infection may be limited, they are highly effective in reducing the burden of disease, severe complications and mortality associated with the virus, especially in at-risk populations such as the over-65s and people with chronic diseases. The article sends a very clear message: annual influenza vaccination is essential, not only to prevent infection, but primarily to protect against severe forms of the disease and save lives.