Travel immunizations

American Family Physician,  July 1, 2004  by Vincent Lo Re, III,  Stephen J. Gluckman

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The standard schedule for administering the hepatitis B vaccine (Recombivax-HB, Engerix-B) in adults 20 years and older calls for three doses of vaccine (each 1.0 mL) at zero, one, and six months. An accelerated schedule with Engerix-B consists of vaccination at zero, one, and two months, with a booster given 12 months after the first dose. (8,25) The vaccine is not contraindicated in pregnancy. (8)

COMBINED HEPATITIS A AND B

A combination hepatitis A and B vaccine (Twinrix) containing the same antigenic components as Engerix-B and pediatric Havrix is available for use in adults older than 18 years. It is as efficacious as each of the monovalent vaccines. (25,26) Primary immunization occurs at zero, one, and six months. An accelerated schedule of zero, one, and three weeks, with a fourth dose 12 months after the first dose, is as efficacious as the standard schedule. (26) Its safety in pregnancy has not been determined.

JAPANESE ENCEPHALITIS

Japanese encephalitis virus, an arboviral infection transmitted by day-biting mosquitoes, is prevalent in the Indian subcontinent, China, Korea, Japan, and other southeast Asian countries. (27) The majority of human cases are asymptomatic, but the virus can cause severe encephalitis with residual neuropsychiatric sequelae.

Japanese encephalitis vaccine (Je-Vax) should be offered to patients who plan to remain for 30 days or longer in endemic areas during the transmission season, particularly if travel destinations might include rural areas. Vaccination also should be considered for short-term travelers who engage in extensive outdoor activities or visit areas of epidemic transmission.

Primary immunization in patients three years or older consists of three doses of 1.0 mL, each given by subcutaneous injection on days zero, seven, and 30. An accelerated schedule, in which doses are given on days zero, seven, and 14, can be used when departure is imminent. (27) The vaccine's efficacy is 91 percent after two doses. (28) [Evidence level A, RCT] A booster dose may be given three years after the primary series if continued exposure in high-risk areas is expected. Because generalized urticaria and angioedema of the face, lips, or oropharynx occasionally have occurred up to two weeks after immunization, the last dose of vaccine should be administered at least 10 days before trip departure. (27,29)

The safety of the vaccine in pregnancy has not been determined. Pregnant women who must travel to an area where the risk of Japanese encephalitis is high should be vaccinated when it is thought that the risks of immunization are outweighed by the risk of infection to the mother and fetus. (27) [Evidence level C, consensus/expert guidelines]

TYPHOID FEVER

Typhoid fever immunization is recommended for travelers going to highly endemic areas in Central and South America, the Indian subcontinent, and Africa. (30) It also is recommended for travelers who may be exposed to potentially contaminated food and drink, such as those journeying beyond the usual tourist routes. (30) Typhoid vaccines (Vivotif Berna, a live-attenuated oral Ty21a vaccine, and Typhim VI) are approximately 50 to 80 percent effective and cannot substitute for careful selection of food and drink.