The presumption here is that we could have been vaccinating people en masse since sometime in spring. However, I do not believe large-scale production of an mRNA vaccine was possible at that time. This does not seem to be the case. My understanding is that manufacturing this type of vaccine is significantly different than other vaccines previously produced at scale (flu vaccine, etc.) so they needed to build out their factories almost from scratch, to the exacting standards required of medical facilities, which likely took many months.

To the best of my knowledge, vaccine makers have been producing the vaccine as quick as they can, planning for hopefully good results, but knowing they could just trash it in the case of bad results, and they only just now have tens of millions of doses.

The FDA needs to make a fast-track vaccine approval process for mRNA vaccines where the pathway to deliver the mRNA has been pre-approved and the only change is in the mRNA payload. However, I don't have much faith in the FDA.

It seems obvious in hindsight, but such trials do have an important role in this process. Not to mention mRNA vaccines are new and it could possibly just have made things worse.

There is plenty of reason to question the safety of mRNA vaccines because none have ever been approved for use in humans.

https://en.wikipedia.org/wiki/RNA_vaccine

Probably a lot. I wonder if we could have some sort of algorithm, or maybe machine learning to maximize human wellbeing for the next pandemic.

How many could have been saved from injecting an untested vaccine on billions of people? What a weird question.

How many could have been killed if we rushed and it turned out to have serious side effects?