Here's one reason why:
https://www.nytimes.com/2020/10/23/health/covid-vaccine-safety.html?action=click&module=Top%20Stories&pgtype=Homepage
You may not be able to access this article if it's behind a paywall. So, I'll quote the article:
"The next job will be to monitor the safety of vaccines once they’re in widespread use. But the administration last year quietly disbanded the office with the expertise for exactly this job, merging it into an office focused on infectious diseases. Its elimination has left that long-term safety effort for coronavirus vaccines fragmented among federal agencies, with no central leadership, experts say."
This is just another example of Trump's failed leadership. We also know he disbanded the pandemic task response force formed by Obama (solely because it had been created by Obama). If the Vaccine Safety Office still existed, it could collaborate with the CDC and drug manufacturers to test the safety of developed vaccines. But noooooo.
Trump "doesn't take responsibility at all"--but all this is his fault nonetheless.
