Perspective:

This is a hot topic of discussion, and the paper has received a lot of attention in the lay press as the Northern hemisphere readies itself for another season of influenza and influenza vaccination. The paper is presented well, and the authors’ review of earlier evidence provides a nice summary. However, I am troubled by a lot of its conclusions and believe the authors have overstretched a bit. Most concerning to me is the lack of association between influenza and AMI after adjustment for confounding factors. The authors state that this might be because their study was underpowered, but the adjusted OR was very close to 1, suggesting that not even a trend was apparent. If this is the case, I wonder how the authors can write that influenza vaccination is ‘protecting’ against AMI since the entire mechanism of its action in protection would be by limiting influenza. My worry is that the authors have confused ‘association’ with ‘causality.’ That is, I do not deny that influenza vaccination is strongly associated with fewer AMIs. But this can be due to a whole host of reasons probably related to a ‘healthy behavior’ effect, as patients who get vaccinated are likely to be quite different than those who do not. I agree with their conclusion that the benefits of influenza vaccination need to be ‘further explored,’ but I am not certain that this study adds that much to this already controversial debate.