Here is an educational resource provided by FDA:
https://www.fda.gov/vaccines-blood-biologics/development-approval-process-cber/vaccine-development-101
One other thing that most folks don't realize is that the FDA regulates manufacturing processes.
I once had a highly-anticipated medical device approved by FDA in a very awkward situation with respect to manufacturing. We got our PMA on March 21, 2001. The story made every major evening news program and every major newspaper in the country. The Secretary of Health and Human Services issued a press release! Very, very rare at that time.
The company stock shot up.
I was responsible for all of the
PR and reported to the COO. We used a big NY firm for
PR execution. But I had to write the releases because there were subtleties.
So we first got approval based on studies in adults. We had to get follow-on approvals for pediatric labeling-- those studies were behind the adult studies. This made me/us turn down the opportunity to have our product in a feature film called Panic Room. The product concept was in the screenplay, but the story had a teenager using it. No bueno. I had to deliver the bad news to the studio.
We also couldn't start selling the product the day we were approved. I had all kinds of government and celebrity people calling to buy our device-- we could not sell it. Why? The product was approved, but we had 2-3 additional approvals related to manufacturing. So it was still not legal to sell.
All of those additional approval steps meant that it took about a year after the product was approved to fully commercialize.