Reports on Thalidomide side effects were ignored, suppressed or dismissed. Distributors sat on such reports for months while continuing to sell the drug. Overall it took several years from the first observed birth defects until the drug was banned in most countries.

https://www.theguardian.com/society/2015/may/25/distillers-k...

Numerous other examples before and after that (including deliberate ignorance of fatigue and medical errors resulting from it) show how medicine elevates institutional interests and groupthink over people's lives.