Consult yr. Dr. or an infectious disease specialist. You also can try the US gov health watch on-line. That said: we have been to both, 1990 and 12/01. Took kids in 1990.
We did not do anything special or have any advance shots. We are ALWAYS carful about eating/drinking off ship. I live in Chicago and Wisconsin water upsets my tummy. I drink coffee (boiled water) or bottled/canned opened in front of me only.