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 mRN

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.