Might as well get the whole schmeil and go for yellow fever, smallpox, measles and take a couple of malaria proph's. as well, no?
Seriously, you don't really need anything to go to AC. And I've had 'em all and carry my yellow card in my passport. The island's about as safe as you could ever expect out of the US--and probably safer than some places in-country.
I won't argue with Hep A, but if it's only to go to AC, it's not necessary.