Completing an immunization schedule before departure is the first and most important step you can take to prevent travel related disease. Travelers often complicate matters by not allowing enough time to be immunized according to established schedules. Although some vaccines can be given on an accelerated schedule, some travelers could be forced to delay their trip or forego essential immunizations. Ideally, you should allow up to 8 weeks before departure in case multiple doses of one or more vaccines are necessary. Vaccines for international travel are summarized below.

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• Cholera: Cholera is an extremely rare disease in traveles from developed countries. Cholera vaccine is recommeded primarily for people at high risk (e.g., relief workers) who work and live in highly endemic areas under less than adequate sanitary conditions.

Cholera vaccine is no longer available in the United States. The manufacture and availability of the injectable vaccine in the United States ceased in June 2000. There is no cholera vaccine that is "officially" required for entry into, or exit from, any country. Despite this, some countries, on occasion, require proof of cholera vaccination from travelers coming from cholera-infected countries. In anticipation of such a situation, certain travelers may wish to carry a medical exemption letter from their health-care provider. Travel Medicine, Inc., recommends that travelers use the International Certificate of Vaccination (Yellow Card) for this purpose, having their health-care provider state "exempt from cholera vaccine" and validate the exemption with both their signature and their official stamp (the "Uniform Stamp" in the United States).

NOTE: Three oral vaccines, including SBL Cholera Vaccine (Biotec AB) and Orochol® (Berna), have recently been developed in Europe but are not yet approved in the United States. The Berna vaccine has been approved in Canada under the name Mutachol. Health Canada advises that Mutachol is not recommended for most travelers, but may be considered for those at higher than average risk, such as health professionals in endemic areas or aid workers in refugee camps. None of the cholera vaccines have been shown to be protective against the O139 Bengal strain of cholera, which has recently emerged in South Asia and has spread to South East Asia.

• Hepatitis A: This vaccine is recommended for all nonimmune travelers over age 2 (over age 1 in Canada) going to areas of intermediate or high risk for hepatitis A transmission, especially frequent short-term travelers or persons staying for extended periods. This recommendation does not include travelers to Japan, Australia, New Zealand, or developed countries in northern and Western Europe (except Spain, Portugal, and southern Italy).

• Hepatitis B: This vaccine is recommended for frequent short-term travelers; persons living for prolonged periods (more than 3 months) in high-risk areas; adventure travelers; travelers with chronic diseases, such as chronic liver disease due to hepatitis C or other causes; people who will have close, prolonged contact with the local population, such as health-care workers, missionaries, and relief workers; and travelers who might have sexual contact with the local population. It should be considered for any risk-averse traveler desiring maximum pre-travel preparation, especially if they are traveling in a country where the sterility of needles and syringes for medical injections cannot be guaranteed.

• Immune globulin: Most travelers' clinics have discontinued immune globulin for the prevention of hepatitis A and rely solely on the hepatitis A vaccine, regardless of time before departure. Immune globulin is still recommended for travelers under 2 years of age since the hepatitis A vaccine is not approved for use under age 2 in the United States. NOTE: In Canada, a hepatitis A vaccine (Havrix) is approved for children down to 1 year of age.

• Influenza: Influenza is transmitted year-round in the tropics. The vaccine is recommended for all travelers over age 50; all travelers of any age with any chronic or immunocompromising conditions; any traveler wishing to decrease the risk of influenza; shipboard travelers along the coast of the United States and Canada; all pregnant women after the first trimester.

• Japanese encephalitis (JE): Recommended for stays of more than one month in rural endemic areas, especially during the peak transmission season; hikers, bicyclists, or others with extensive outdoor exposures in endemic area; repeated short visits to rural farming areas of all islands, such as may occur with long-term expatriates.

• Measles/Mumps/Rubella: All travelers to endemic or epidemic areas should be vaccinated if they have not had these illnesses or have not been appropriately immunized.

• Meningococcal (meningitis): Recommended for all travelers staying longer than 1 month during the dry season in the meningitis belt countries of sub-Saharan Africa; all travelers during the dry season if prolonged contact with the local populace is anticipated; and all travelers into epidemic regions. The vaccine is required for travelers to Saudi Arabia for purpose of pilgrimages to Mecca.

• Pneumococcal: Advised for travelers over 65, those with chronic illnesses, or people who have had a splenectomy.

• Polio: Immunized travelers over age 18 should receive a one-time polio booster prior to international travel.

• Rabies: Recommended for all stays of over 30 days in risk areas, especially children; shorter stays at locations that are more than 24 hours in travel time from a reliable source of postexposure rabies vaccine; occupational exposure; and all adventure travelers and backpackers to risk areas. Consider for shorter stays in risk-averse travelers desiring maximum protection.

• Tetanus/Diphtheria: Booster every 10 years, for adults. Diphtheria protection is important, especially for adults, 60% of whom have little or no immunity to this disease.

• Typhoid: Recommended for travelers going to endemic areas, especially lesser-developed countries, who will be staying for a prolonged period of time, eating adventurously, or venturing off the usual tourist routes into small cities, villages, and rural areas. Consider for short-term travel in those desiring maximum protection.

• Varicella (chickenpox): Adolescents and adults who have never been immunized, or have not had the disease, should be vaccinated. Immigrants from developing countries are at particular risk.

• Yellow fever: Vaccination may be required for entry into certain countries in the yellow fever endemic zones, and/or recommended for protection in certain yellow fever endemic zone countries with active disease.