I think the only metric that matters is total medical care provided on a national / global scale.
It may take vastly more training but on average a full annual physical provides less benefit on average than a 30 second vaccination requiring minimal training. Value creation and skill are wildly different things in the medical profession.
After you've had that 30 second vaccination, the second same 30 second vaccination provides next-to-no added benefit, but the physical does.
There is no reason the medical field needs to gate keep injections. Anyone can inject, you don't need a nurse. Maybe as far as an IV with some very basic training.