It wasn’t exactly “fast tracked,” a little misleading phrase (not helped by the official name of the operation called “warp speed”) that I think makes people more nervous than they need to me. This kind of implies they didn’t go through the same testing as other vaccines. They have gone through the same stringent criteria as any other vaccine at this point. A lot of what was done to speed things up was the government subsidizing and risk guaranteeing, so multiple steps in vaccine testing and deployment could be done in parellel rather than in series. Normally you wouldn’t be mass producing experimental vaccine doses or medications before you know they work, or else you’ve wasted a ton of money. To speed things up the government basically said they would cover the losses on the vaccines if they ended up being useless. This allowed production of these vaccines to start being distributed as soon as the research was complete. Otherwise they wouldn’t have been churning out millions of doses already with a lot already stockpiled and giving doses of it to icu staff only three days after it got emergency authorization (full formal approval would follow about nine months later).

Honestly people get way more nervous about vaccines than they really need to be. Some of the lowest risk things we use in all of medicine. Though not that they shouldn’t be, since they’re deployed on such a mass scale.