Nah you should be fine as far as vaccinations go to be honest mate. Most of these cruises are aimed at Americans who (believe it or not) are sometimes suprised that they actually even need a passport. I'm they must be informed when they book , but quite a few still manage to turn up without one & give the pratica nightmares ! Haha
Think you'd only really need to worry about jabs if your doing more specialist cruises say in the Amazon or somewhere.
Just remember to double check that your visa is a C1 & once you've done that. Check it again to be sure !