i think you've gotten some good advice so far. If you really want to do some type of vaccine research--and you feel you can't do that at irvine--you can always apply to take a year off to do an hhmi/doris duke program.
i'm not trying to be a jerk here, but there are a lot of good reasons for picking a specific school: Close to family/loved one, cost, dual-degree options, unique curriculum, etc. However, picking a school based on one research department, especially since you aren't md, phd (and it doesn't sound like you're interested in switching into an md, phd program), doesn't seem like a particularly convincing reason.
to me, it seems like you think you'll have a lot time to do research in med school. In my case, i did basic and translational research during and after college for a few years: I can work independently and i have the skills such that were i to start med school all over again, i could have been capable of doing a basic research project (granted, it would have been difficult). Instead, i opted to get involved in two clinical projects and one public health project. Why? Because they require less commitment, and unlike basic research, i can put plasma samples in a -80 for two weeks while i study for an exam; i can't make cell cultures or mice wait for two weeks while i'm busy.
if you have no interest in getting a phd, i think you should remove the element of umd's vaccine opportunities from your list of reasons to decide between umd and uci.
also, i don't know why no one else has said this: Irvine/orange>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>baltimore. The only nice thing about baltimore is the waterfront, and even that is only nice during the day