Each year more than 20 million Americans travel abroad to rural areas or developing countries. Assessing an international traveler's risks will ensure that the proper immunizations are given. Thanassi reviews a six-step approach (see the accompanying table) to the immunization consultation.

When evaluating the special immunization needs of travelers, consideration must be given to older people, pregnant women, children and immunocompromised persons. For healthy elderly persons, as well as for travelers with chronic obstructive pulmonary disease and asthma, a one-time pneumococcal vaccine and an annual influenza immunization should be administered. Older adults who are taking gastric acid blockers should be considered for cholera vaccination when traveling to an endemic area. In pregnant or immunocompromised travelers, live-virus vaccines (such as those for measles, mumps, rubella [MMR], oral polio and yellow fever) and attenuated live vaccines (such as oral typhoid) are contraindicated. Immunization requirements for children are similar to those for adults, although it is important to remember that yellow fever vaccine is absolutely contraindicated in children younger than four months of age and generally contraindicated in those younger than nine months.

Adults who have not completed their routine series of childhood immunizations should receive “catch-up” vaccinations for tetanusdiptheria, MMR and poliovirus. Vaccination for varicella is appropriate for nonimmune travelers. A tetanus booster should be given to any traveler who has not been appropriately vaccinated within five years. A one-time adult polio booster is appropriate for travelers to developing countries in the Eastern Hemisphere.

The three most common tropically acquired febrile illnesses in returning travelers are hepatitis A, typhoid fever and malaria. Influenza also carries a high morbidity. Immunization for hepatitis A should be provided to travelers going outside developed areas. Typhoid vaccine should be administered to those staying in endemic areas for over two weeks. Influenza vaccine is appropriate when travelers are visiting an area during its influenza season.

Entry requirements of the country to be visited may require yellow fever vaccination, which is strongly recommended for travelers to South America and rural areas of equatorial Africa. A booster is needed only once every 10 years. Geographically indicated immunizations include cholera for persons traveling to tropical Africa, Asia and South America (although the cholera vaccine is only 50 percent effective) and meningococcus for those traveling to Nepal, northern India, Saudi Arabia and the “meningitis belt” across sub-Saharan Africa. Tick-borne encephalitis, which occurs in the forests of Europe and the former Soviet Union, can be contracted from a carrier tick between April and August. Immunization for this condition is not available in the United States but can be obtained in Europe. For overseas stays of more than one month, the traveler should consider immunization against hepatitis B, Japanese encephalitis, rabies and, in certain circumstances, the plague (Yersinia pestis).

The author concludes that general guidelines for immunization of international travelers are helpful, but that the individual needs of specific travelers vary.

editor's note: Recommendations for vaccination before travel vary depending on the source. Cholera risk, for example, is very low, and this vaccine is generally not recommended for most tourists. The availability of both an oral typhoid vaccine as well as a parenteral preparation gives clinicians more choices in administration routes. More detailed information is available in Health Information for International Travel, published biannually by the Centers for Disease Control and Prevention (CDC). Up-to-date automated information is available from the CDC (telephone: 888-232-3228) or on the Internet at www.cdc.gov under “Traveler's Health.”—r.s.