you don't exactly need anything, but sound advice include diphteria and tetanus boosters as well as immune globulin or other immunization against Hep.A which spreads easily and could get fairly nasty without being critical.
Malaria pills are usually not recommended if you are staying at resorts. If you are planning to stay overnight by the Haitian border or in low lying areas in the interior parts of the country, you may want to consider prophylaxis or at least sleeping under a net and using insect repellent.
If you have small children along, beware of measles if your children are not immunized.
For more advice, try the CDC - Centers for Disease Control, Atlanta, USA - website, link below. Just bear in mind that they tend to err on the side of safety.
And remember to consult your own physician.
Regards,
Susanne
