So until we have enough data to understand the effect of vaccination on the spread of covid, the vaccines should be allocated preferentially to those expected to lose the most if they are not vaccinated.
Hospitals run on three things -- Space, Stuff, and Staff. Space is probably the easiest to expand in an emergency, you set up a bunch of beds in a garage or tent and call it a field hospital. Won't be up to the usual standards, but it'll give you some place to stash the incoming crunch. Stuff depends on foresight and money (and lacking that, your ability to scavenge and improvise), the general public is well aware of PPE shortages but it's also categories of things like sedatives, bags of IV solution, CRRT machines, etc.
And then there's Staff. There is also a strategic reason for vaccinating medical residents (along with nurses and other medical staff) -- the goal is not necessarily to reduce the mortality rate of these medical personnel, but to preserve capacity. Staff can be moved around, there are travel nurses and locum tenens docs that can be shuffled to where they are needed.. The problem is when a crunch happens across broad areas, which is what we're heading into now.