This first point is super important, and one of the reasons that vaccine development is different from other treatments.Wait to see if there are negative reactions to the vaccine. If there are, vaccine is scrubbed.Wait to see how much more the vaccinated group is protected compared to the placebo. To be effective, it should be 50% more protected.
For say a cancer drug. You've got something that you think may work, and offers some incremental improvement. It may have some wild side effect. But, the comparison is between "this very sick person where cancer is actively killing them and the side effect isn't as bad as death". Lots of room in there
But, a vaccine is given to someone who is healthy and not sick. There's nothing actively killing them. Which makes "let's give this healthy person something that causes a negative side effect" a much more difficult proposition.
Vaccine's have insanely high safety testing because of this. It's harder to do trials for the same reason. That cancer patient is able to take much more risk, the alternative is death. We're not willing to subject a healthy person to the same level of risk.
If the testing is done correctly and not rushed for political reasons, the process is supposed to prevent this. Which is part of why the timeline is so long.Crazy scenario, but let's say one or more vaccines pass Phase 3, and vaccine dosages begin publicly; then a few months later noticeable side effects and long term issues show in those vaccinated....is that "normal"? would they pause and go back to the drawing board, and recall the vaccine?
There's steps in the development that risking and spending extra money can accelerate, but there's other steps where it just takes time and there's no way to go faster without sacrificing safety. The easy one is starting spending on the next steps, like manufacturing capacity before the prior step is done. Normally, you would wait until you know something works before spending the money. But, willing to risk the cash, that it's all spent and then it doesn't work so it's all wasted money and the next step never happens. Doing that means you can start those tasks before the prior one is done, so it's ready on the day you move to the next step.
Another reason testing is so hard. There's differences between men and women, and more again to pregnant women. Add in that testing the impact on childbirth is always going to take a longer time with no way to accelerate the timeline.I can't imagine they have pregnant people in the trials, they wait to get the vaccine or take a chance? I'm thinking Thalidomide where the problem didn't show up until some detective work was done
Worth noting too, the FDA never approved Thalidomide.