From the abstract:
> Propensity-score matching (PSM) was used to create flu-vaccinated and flu-unvaccinated cohorts with similar baseline demographics, medication usage, and comorbidities.
If you want to argue that the authors did a bad job at this, for some reason, that would be a really meaningful contribution and I'd love to hear the details.
Otherwise, can we assume that the scientists writing and reviewing papers did a semi-competent job and are at least as good at analyzing quantitative claims as someone commenting on HN because they are bored at work?