Well - first, we don't get paid by the rx - mostly on salary/hourly, etc....
If the rx count increases, so does our labor model - we get more staff to compensate - really no busier than any other day, particularly since the actual rx can be run anytime - it doesn't have to be run at the time you give the injection.
From the public health perspective, it is more available at a pharmacy than anywhere else. Just try to get into see a physician for a URI & you wait 5 days in my area (fortunately long enough for the URI to resolve), so a flu shot appt is waaaaay down there on the list of "needs to be seen" pts.
In my area, there are no nurses to give the injections. We have a huge shortage of nurses, so pharmacists do them.
Flu shots are a huge money maker for the corporation/pharmacy, altho the individual pharmacist doesn't make any more money.
Its also a way to get out there & talk to your patients about all sorts of things. You'd be surprised what comes up in that conversation. You build trust, credibility, reinforce accessibiliity & frankly spend the time with the patient the physician can't/won't.
As for students in CA giving them - yes they can, after training & certification. But, actually giving them will depend on whatever contractual arrangement the pharmacy/corporation has with the school. At that point, it becomes a matter of liability coverage the school carries for the student in an out-of-school setting. If I have an intern on a rotation, they can do it under my supervision. But, if I have an intern who is just working & not on a rotation, no they cannot, even if its the same intern. It gets complicated, but has to do with what our contract with the school is & whose liability coverage applies.
For pharmacists administering - be sure your liability coverage extends to injections - not all do. Even more important for those who don't carry their own coverage - make sure your employer liability covers extended services like these.