Huh? Anyone could sign up for the trial, even after I participated in one I still got calls from countless trial recruiters from other manufacturers. It was quite easy to participate
What if, at any time, you could walk into your doctor's office and say "I'm ready for that experimental vaccine?" You could contribute your data to the pool that increases our confidence in its efficacy. As confidence gets stronger, more people volunteer. Eventually, third party labs (maybe regulators like the FDA - maybe NGOs like the UL) certify that they believe a vaccine is safe and effective, which makes even more people comfortable getting it.
If we had done that, how would life be different now? Could we have closed fewer things? Would more people have led a more normal/less stressful lives? Would we be closer to being done with this mess? How many fewer long-term ramifications (health, financial, social, developmental, psychological, mortal) would people have to deal with?
We reconsidered, reenvisioned, and reinvented so many things this year. Why can't we apply that same mindset here too?
I mean, take the flu shot. The times I've gotten it I've not had any reaction or one so mild I don't remember. Maybe a sore arm? Slightly tired, though that could have been work. I wouldn't personally know until they do blood tests.
Even if you have side effects - outside of a possible sore arm, you wouldn't know it was the vaccine or just unfortunate timing for a virus or something.
You want the trial to be double blind because it means there is less bias: https://www.verywellmind.com/what-is-a-double-blind-study-27....
I don't know what the poster above was talking about, getting calls to participate in a study. Nobody contacted my wife or I with such offers. I suspect that the poster was lucky to live right in a city where the test was being conducted; those outside of major cities are probably not included in his claim that anyone could participate in the trials.
Sometimes it just doesn't work to have double blind: LSD trials, for example, make things pretty obvious. It isn't the case for the flue, though.
You are correct on the trials: most folks don't get called. That said, living outside the city doesn't exclude you from trials in general because they generally need participants with x and/or y. Often, they will pay for expenses to travel, especially if your disease is uncommon or they have trouble finding participants.