Influenza occurs in the winter season in temperate areas and year-round in the tropics. Vaccination should be considered in older travelers and persons with chronic medical conditions.

The pneumococcal vaccine is recommended for travelers over age 65 and those with chronic medical conditions.

Tuberculosis has a worldwide distribution. Long-term travelers may want to consider getting a skin test prior to departure. Travelers with negative skin tests should have a repeat test after returning. The BCG vaccine is of uncertain efficacy.

For some diseases, there is no specific prophylaxis available. Insect precautions are recommended to reduce the risk of dengue fever, leishmaniasis, filariasis, Lyme disease, trypanosomiasis, and other arthropod-borne illnesses. Swimming in fresh water may carry a risk of schistosomiasis : it is best to restrict swimming to chlorinated pools or salt water (upstream from sewage or waste dumps).