Regulators can decide they're uneasy about potential for birth defects, or side effects with particular other drugs you never tested, or any number of issues. Sometimes a pharmaceutical company just hoped not to be asked, and other times the concern comes out of the blue.

But if we're fast-tracking approval, anything that isn't a red flag won't get in the way. That unavoidably means higher risk to patients overall. Since the virus kills a lot of people every day everywhere it hasn't been eliminated it makes sense to take that risk, but governments (accountable to their citizens) get to decide that, not drug companies.

The trials are most certainly accelerated. Take a look at Moderna's trial of their RNA vaccine.[1]

It's a 2 year trial, but data is collected on a rolling basis. They aren't waiting 2 years for final results, I'm guessing they do a few interim analyses until they see the two arms split in terms of infection rate. Then they'll go to the FDA and see if that's sufficient for approval.

And look at the N-size. 30,000 people for a drug that will be given (potentially) to billions of people. To make a comparison, Gardasil, the HPV vaccine was tested in ~28,000 individuals over 3-4 years.[2] And Gardasil is used in a much more limited population than the Covid vaccine will be.

[1]https://clinicaltrials.gov/ct2/show/NCT04470427?term=mRNA-12... [2]https://www.fda.gov/files/vaccines,%20blood%20&%20biologics/...

(It wouldn't be HN without a splash of pedantry; apologies in advance.)

I'm curious what you mean by this. Women constitute slightly more than half of the population, no? There are probably billions of women at this point who have had Gardisil administered.

https://www.cancer.org/cancer/cancer-causes/infectious-agent...

And it's not limited to women now. Different countries have it approved/covered for men of different ages. I (as a man) recently finished the full course, though I had to pay for it out of pocket.

So Gardasil is only approved for "girls and women 9 through 26 years of age". Plus there wasn't much expectation of use outside of Western countries initially since it's not cheap and there are likely higher priority vaccines in developing countries (i.e. do you spend dollars on this or meningitis vaccines?). Use is probably pretty broad now, ~10 years post-launch.

Eventually they expanded the label to include "boys and men 9 through 26 years of age".

So all in all, a relatively small slice of the population, where for the Covid vaccine, they're trying to get it approved for pretty much everybody.