[learc83]

The study didn't control for the differences in the vaccinated and unvaccinated groups. Children with chronic medical conditions are more likely to be vaccinated, and some preliminary reports show a correlation between medical conditions that indicate flu vaccination and narcolepsy [1]. And from what I can tell, the control group didn't exclude kids vaccinated with other H1N1 vaccines.

Because of that, that study can't say that the 4x higher number is the relative risk of taking Pandermrix.

There are also issues with potential over diagnosis and recall bias because of public awareness of the issue through the media [1].

The real problem is that this effect is so small, not that the effect takes years to develop. We're talking 4 cases of narcolepsy per 100k kids. Even a 10 year long study of 30k Phase 3 vaccine participants is unlikely to discover something like that.

Nearly all new drugs that are released could have similar side effects. It's just not feasible to conduct studies large enough to discover them until you start rolling it out to millions of people.

1.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4962758/