Harrisons Manual of Medicine, 18th Ed.

CHAPTER 214. Immunization and Recommendations for Travelers

IMMUNIZATION

Few medical interventions of the past century can rival the effect that immunization has had on longevity, economic savings, and quality of life.

VACCINE IMPACT

• Vaccines have both a direct impact (protecting the vaccinated individual against infection) and indirect effects (reducing transmission of infectious agents from immunized people to others).

• Vaccine programs attempt to control, eliminate, or eradicate a disease.

– Control programs: limit the disruptive impacts associated with outbreaks in a defined geographic area

– Elimination programs: require a blockage in the indigenous sustained transmission of an infection in a defined geographic area, with possible importation of sporadic cases from other areas requiring ongoing interventions

– Eradication programs: considered successful if elimination of a disease can be sustained without ongoing interventions. Smallpox is the only vaccine-preventable disease that has been globally eradicated; considerable effort is ongoing in attempts to eradicate polio.

IMMUNIZATION PRACTICE STANDARDS

• Figure 214-1 summarizes the adult immunization schedules for 2011.

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FIGURE 214-1 Recommended adult immunization schedules, United States, 2011. For complete statements by the Advisory Committee on Immunization Practices (ACIP), visit www.cdc.gov/vaccines/pubs/ACIP-list.htm.

• Before vaccination, pts must be screened for contraindications (conditions that substantially increase the risk of a serious adverse reaction) and precautions (conditions that may increase the risk of an adverse event or that may compromise the ability of the vaccine to evoke immunity). Table 214-1 summarizes the contraindications and precautions for vaccines used commonly in adults.

TABLE 214-1 CONTRAINDICATIONS AND PRECAUTIONS FOR COMMONLY USED VACCINES IN ADULTS

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• A vaccine information statement must be provided to all vaccine recipients; current VISs are available online at www.cdc.gov/vaccines andwww.immunize.org/vis/. (The latter website includes translations.)

• Any adverse event that occurs after immunization and that may or may not be related to the vaccine should be reported to the Vaccine Adverse Event Reporting System (www.vaers.hhs.gov).

RECOMMENDATIONS FOR TRAVELERS

Travelers should be aware of various health risks that might be associated with given destinations. Information regarding country-specific risks can be obtained from the CDC publication Health Information for International Travel, which is available at www.cdc.gov/travel. Travelers should be encouraged to see a travel medicine practitioner before departure. Although infections contribute substantially to morbidity among travelers, they account for only ~1% of deaths; in contrast, injuries (e.g., motor vehicle, drowning, or aircraft accidents) account for 22% of deaths.

IMMUNIZATIONS FOR TRAVEL

There are three categories of immunization for travel.

• Routine immunizations (see Fig. 214-1) are needed regardless of travel. However, travelers from the United States should be certain that their routine immunizations are up to date because certain diseases (e.g., diphtheria, tetanus, polio, measles) are more likely to be acquired outside the United States than at home.

• Required immunizations (e.g., yellow fever vaccination) are mandated by international regulations for entry into certain areas.

• Recommended immunizations (e.g., hepatitis A, typhoid) are advisable because they protect travelers against illnesses for whose acquisition they are at increased risk. Table 214-2 lists vaccines required or recommended for travel.

TABLE 214-2 VACCINES COMMONLY USED FOR TRAVEL

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PREVENTION OF MALARIA AND OTHER INSECT-BORNE DISEASES

• Chemoprophylaxis against malaria and other preventive measures are recommended for travel to malaria-endemic regions, particularly since fewer than 50% of travelers adhere to basic recommendations for malaria prevention.

• Chemoprophylactic regimens consist of chloroquine, doxycycline, atovaquone-proguanil, or mefloquine.

• In the United States, 90% of cases of Plasmodium falciparum infection occur in persons returning or immigrating from Africa and Oceania.

• The destination helps determine the particular medication chosen (e.g., whether chloroquine-resistant P. falciparum is present), as does the traveler’s preference and medical history.

• Personal protective measures against mosquito bites [e.g., the use of DEET-containing insect repellents (25–50%), permethrin-impregnated bed nets, and screened sleeping areas], especially between dusk and dawn, can prevent malaria and other insect-borne diseases (e.g., dengue fever).

PREVENTION OF GASTROINTESTINAL ILLNESS

• Diarrhea, the leading cause of illness in travelers, is usually a short-lived, self-limited condition, although 20% of pts are confined to bed.

• Incidence rates per 2-week stay approach 55% in parts of Africa, Central and South America, and Southeast Asia.

• Travelers should eat only well-cooked hot foods, peeled or cooked fruits and vegetables, and bottled or boiled liquids (i.e., “boil it, cook it, peel it, or forget it!”).

• The most common etiologies of travelers’ diarrhea are toxigenic and enteroaggregative strains of Escherichia coli, although Campylobacter and norovirus are common in certain circumstances.

• Travelers should carry medications for self-treatment.

– Mild to moderate diarrhea can be treated with loperamide and fluids.

– Moderate to severe diarrhea should be treated with a 3-day course or a single double dose of a fluoroquinolone.

• High rates of quinolone-resistant Campylobacter in Thailand make azithromycin a better choice for that country.

• If fever and hematochezia are both absent, loperamide should be taken in combination with the antibiotic.

• Prophylaxis with bismuth subsalicylate is ~60% effective; for some pts (athletes, pts with repeated travelers’ diarrhea, and persons with chronic diseases), a single daily dose of a quinolone, azithromycin, or rifaximin during travel of <1 month’s duration is 75–90% effective.

PREVENTION OF OTHER TRAVEL-RELATED PROBLEMS

• Travelers are at high risk for sexually transmitted diseases preventable by condom use.

• Schistosomiasis can be prevented by avoidance of swimming or bathing in freshwater lakes, streams, or rivers in parts of northeastern South America, the Caribbean, Africa, and Southeast Asia.

• Travel-associated injury can be prevented with common-sense precautions: not riding on motorcycles and in overcrowded public vehicles, not traveling by road in rural areas of developing countries after dark, and not drinking excessive amounts of alcohol.

• Walking barefoot should be avoided given the risk of hookworm and Strongyloides infections and snakebites.

TRAVEL DURING PREGNANCY

• The safest part of pregnancy in which to travel is between 18 and 24 weeks, when the risk of spontaneous abortion or premature labor is low.

• Relative contraindications to international travel during pregnancy include a history of miscarriage, premature labor, incompetent cervix, or toxemia or the presence of other general medical problems (e.g., heart failure, severe anemia).

• Areas of excessive risk (e.g., where live virus vaccines are required for travel or where multidrug-resistant malaria is endemic) should be avoided throughout pregnancy.

• Malaria during pregnancy carries a significant risk of morbidity and death for both the mother and the fetus.

THE HIV-INFECTED TRAVELER

• HIV-seropositive persons with depressed CD4+ T cell counts should seek counseling from a travel medicine practitioner before departure, particularly when traveling to the developing world.

• Several countries routinely deny entry to HIV-positive persons for prolonged stay, even though these restrictions do not appear to decrease rates of transmission of the virus.

• Ensuring that HIV-infected pts’ immunizations are up to date is critical, as many vaccine-preventable diseases are particularly severe in this population.

• Malaria is especially severe in pts with AIDS; the HIV load doubles during malaria, with subsidence in 8–9 weeks.

PROBLEMS AFTER RETURN FROM TRAVEL

• Diarrhea: After travelers’ diarrhea, symptoms may persist because of the continued presence of pathogens (e.g., Giardia lamblia) or, more often, because of postinfectious sequelae such as lactose intolerance or irritable bowel syndrome. A trial of metronidazole for giardiasis, a lactose-free diet, or a several-week trial of high-dose hydrophilic mucilloid (plus an osmotic laxative such as lactulose or PEG 3350) may relieve symptoms.

• Fever: Malaria is the first diagnosis that should be considered when a traveler returns from an endemic area with fever. Malaria is acquired most often in Africa, dengue in Southeast Asia and the Caribbean, typhoid fever in southern Asia, and rickettsial infections in southern Africa.

• Skin conditions: Pyodermas, sunburn, insect bites, skin ulcers, and cutaneous larva migrans are the most common skin conditions in returning travelers; if persistent, a diagnosis of cutaneous leishmaniasis, mycobacterial infection, or fungal infection should be considered.

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For a more detailed discussion, see Schuchat A, Jackson LA: Immunization Principles and Vaccine Use, Chap. 122, p. 1031; and Keystone JS, Kozarsky PE: Health Recommendations for International Travel, Chap. 123, p. 1042, in HPIM-18.