Frankly, I'm surprised that the global expedited vaccine enterprise has gone as well as it has so far. Fundamentally it's like a bunch of dudes charging up a hill to take a machine-gun bunker... you expect casualties and you don't know exactly who, when, or how many. I'm surprised they're approaching the top and nobodies been gunned down yet (just a few flesh wounds).
I think a key factor in reducing the "casualties" is technology, we are able to target specific biological effects better and also steer clear of some known landmines (many decades of vaccine development experience have taught us a few things NOT to do). In this case it's not 19 y/o 'Nam-era draftees charging the hill, it's probably national mission force guys.