I'll use the vaccine tests as a good example, but there are plenty. The studies were of large cohorts, around 30k in each group if I remember correctly. They w

I'll use the vaccine tests as a good example, but there are plenty. The studies were of large cohorts, around 30k in each group if I remember correctly. They were only followed for roughly 1 month, as soon as enough subjects were symptomatic they lifted the veil and exposed which was the placebo group. Individuals weren't tested for a Covid infection unless they self-reported symptoms during the study. That structure of a study is fine for helping find the risk of immediate adverse effects of the vaccine. It doesn't day anything of how well spread is contained, how long the protection lasts, or the risk of long term adverse impact. All that to say those risks simply weren't known. There wasn't any reason to say they risks existed at any meaningful level, only that the scientific studies done didn't prove the claims often made with regards to the safety and efficacy of the vaccines.