Chapter 84 Travel Medicine
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International travelers, particularly those participating in wilderness and outdoors activities, have unique health needs based largely on their underlying health and specific geographic destination.89 Exposure to unfamiliar cultures, poor sanitation, and harsh environments may have a deleterious effect on health and interfere with the purpose and enjoyment of the trip.
The multidisciplinary specialty of travel medicine borrows principles from the fields of public health, infectious diseases, tropical medicine, and environmental and wilderness medicine. Travel medicine integrates features of these other disciplines with geographic and chronologic data, to formulate an approach to health risk assessment for a given journey.93
Sources of Information
As a basic introduction to travel medicine, this chapter will focus on advice for the healthy U.S. adult traveler. Closely related topics are covered extensively in other chapters. Pediatric and unhealthy travelers are beyond the scope of this chapter. Excellent information about travel medicine–related vaccines for children has been published,35,100,116 and reference tables for both drugs and vaccines can be found at www.istm.org (see Appendix). A review on the approach to travelers with underlying medical conditions was recently published.62
The Centers for Disease Control and Prevention (CDC) publishes several authoritative sources of information on travel medicine. Health Information for International Travel, commonly called the “yellow book,” is updated annually. Two other periodicals, the weekly Morbidity and Mortality Weekly Report (MMWR) and Summary of Health Information for International Travel (the “blue sheet,” published biweekly), provide updated information on the status of immunization recommendations, worldwide disease outbreaks and changes in health conditions. A reliable way to obtain current travel health information, including vaccine requirements, malaria chemoprophylaxis, and disease outbreaks for various regions of the world is to consult the CDC Database of Health Information for International Travel web-site (www.cdc.gov/travel/yb/index.htm). For nonmedical information of interest to the traveler, the U.S. State Department can be accessed at travel.state.gov/. Additional resources for travel medicine information are given in the Appendix, located at the end of this chapter.
Professional societies, foundations, and private publishers7 are additional sources of telephone advice, topical brochures and information sheets, newsletters containing information on travel medicine topics, schedules of travel medicine meetings and continuing education courses, and other information, including lists of travel medicine clinics in the United States and abroad and English-speaking physicians worldwide. A convenient way to access both official and proprietary information sources can be found at the home pages of the International Society of Travel Medicine (www.istm.org) and the American Society of Tropical Medicine and Hygiene (www.astmh.org), where links can be found to the CDC, World Health Organization (WHO), and other websites, where the health needs for individual itineraries can be explored. The Infectious Disease Society of America also has guidelines for travelers.7,80
Standard textbooks on infectious diseases and tropical medicine and a number of monographs on travel medicine provide in-depth information on travel medicine–related subjects; many of these resources are listed in the suggested readings at the end of the chapter. A number of computer-based interactive programs for travel medicine clinics are commercially available. The best sources of current information on travel medicine software are published reviews and “hands-on” demonstrations at medical and scientific meetings.
American travelers abroad who experience an emergency of any sort should contact the nearest U.S. consulate or embassy or call the U.S. Department of State (see Appendix). If an extended stay in a given country is planned, the traveler should register with the consulate or embassy shortly after arrival in the country.
Several months in advance of departure travelers should ascertain whether their health insurance policy covers the costs of treatment and hospitalization for illness or injuries occurring abroad. They should consider a policy that covers emergency medical evacuation back to the United States, particularly if their travel involves remote locations where medical care is marginal or nonexistent. For example, insurance for helicopter rescue evacuation if trekking in the Himalayas is important. Medicare usually covers only health care expenses arising in the United States and its territories. Some credit card services provide worldwide medical referrals and arrangements for emergency transportation for their cardholders but do not actually cover the costs incurred. What the traveler needs is a short-term health insurance policy that specifically covers medical expenses and medical evacuation during foreign travel. Depending on the insurer, chronic medical conditions may be excluded, or covered only if they are certified to be under control for a period of time before departure. Elderly travelers may find it more difficult to get medical insurance of this kind.
Travel Health Risk Assessment
Pre-travel medical preparation is individualized by review of the geographic destination, duration and purpose of the trip, style of travel, underlying health of the traveler, and access to medical care during the trip (Box 84-1).166 Information about the level of sanitation and environmental hazards at the destinations can be used to identify special health concerns; likewise, risk assessment includes whether the traveler might be exposed to extreme weather conditions, high altitude, or aquatic activities. In this context, immunizations and prevention and self-treatment of malaria and traveler’s diarrhea are always addressed. Prevention and treatment of common ailments such as jet lag, motion sickness, sun exposure, altitude illness, and insect and animal bites should be reviewed when the issues are appropriate to the specific itinerary. Some attention, at least in patient education brochures, should be given to personal safety, sexually transmitted diseases, prevention of vehicular trauma, and emergency medical evacuation.
BOX 84-1 History for Travel Risk Assessment
General and Special Personal Health Issues
Multiple destinations and travel lasting longer than a few weeks increase the complexity of the medical preparation; the content of the travel medical kit becomes more inclusive with longer travel, because a greater number of health needs over time can be anticipated. Travelers staying in urban, air-conditioned hotels or well-developed resorts have less exposure to mosquitoes than do those camping or living among residents in small villages. If accommodations in malarious areas are in un-screened rooms, travelers should plan to take with them portable bed nets and permethrin-containing knock down sprays against mosquitoes and other biting insects. Teachers, students, missionaries, relief workers, agricultural consultants, field biologists, and adventure travelers are more likely than persons on standard tourist packages and business travelers to be exposed to endemic infectious diseases. Such diseases include those transmitted by the local residents (e.g., hepatitis B, tuberculosis, and meningitis), insect-borne diseases (e.g., malaria, yellow fever, leishmaniasis, filariasis, plague, and typhus), and diseases associated with animal exposure (e.g., rabies, leptospirosis, and anthrax). Travelers need also to be aware of the risks of blood-borne infections from the use of contaminated needles, syringes, and other medical or dental devices during such events as emergency dental care, injections, tattoos, and transfusions.
All travelers should be cautioned about the hazards of unprotected sexual contact with new partners, especially with commercial sex workers. Gonorrhea and chlamydial infection common in the industrialized world have worldwide distribution. Human immunodeficiency virus (HIV) infection, syphilis, chancroid, and lymphogranuloma venereum are more prevalent in the developing world.
Most international travelers should begin pre-travel medical preparation 4 to 6 weeks before their date of departure so that multidose immunization schedules can be completed, protective immunity developed, and necessary medications and special supplies can be obtained. Medical preparation for an international trip to many tourist destinations is relatively straightforward for people in good health. However, advance planning and consultation with a travel medicine expert are recommended for people with allergies, special health needs (e.g., pregnancy, infancy, advanced age, and handicaps), or chronic or underlying health conditions (e.g., cardiovascular disease, respiratory conditions, compromised immune status, diabetes, renal failure, organ transplants, and seizure disorders).
Vaccine-preventable diseases (e.g., diphtheria, measles, polio, hepatitis, and typhoid fever) and exotic infectious diseases (e.g., malaria, schistosomiasis, leishmaniasis, and trichinosis) are important39,41; however, cardiovascular diseases and trauma account for more morbidity and mortality among American travelers and expatriates than do infectious diseases. This underscores the importance of addressing not only the traveler’s health needs but also educating him or her about accident prevention.
Injuries are the leading cause of preventable death among travelers. Road traffic accidents account for the majority of injury-related deaths.75,140,190 If travelers consider driving an automobile in a developing country, they must be aware of the possible lack of safety features on the rented vehicle, poorly maintained roads, and sometimes very different behavior of local drivers. Even driving in a developed country can be hazardous when signs cannot be read or the traffic pattern is reversed from what is customary for the traveler. If the traveler rides bicycles, mopeds, or motorcycles, he or she should insist on wearing helmets. The traveler should avoid driving any vehicle at night and should never drink alcohol and drive. Injuries due to falls, drowning, animal bites, fire, and poisoning are also important causes of travel-related morbidity.
Travelers who participate in relief or other activities in regions affected by political unrest, war, terrorist activity, famine, or natural disaster represent special problems in preparation. Ideally, such travelers who know they might volunteer for such activities should try to prepare themselves well in advance and receive immunizations so that they are prepared for travel to virtually any part of the world. Likewise, such travelers might face unique risks when an outbreak of disease is occurring at the destination. For instance, if they must work where avian influenza is actively being transmitted, it is logical to consider oseltamivir prophylaxis or self-therapy in the event they develop a flu-like illness. If an outbreak of plague is occurring, they might consider taking doxycycline for both malaria prevention and protection against plague, because plague vaccine is not readily available and requires an extended series of injections. If SARS or one of the hemorrhagic viruses is a concern, they must plan to arrive with enough gloves, gowns and the correct type of masks to practice appropriate infection control precautions. Too frequently, volunteers, anxious to help in the face of a disaster, literally fly off poorly prepared to protect their own health.
All travelers should remain vigilant to help guarantee their personal safety. They should consciously avoid risky situations. Up-to-date information concerning personal risk at destinations can be obtained from the U.S. Department of State website (www.state.gov). Sometimes overlooked among travelers to politically dangerous locations is the possibility of kidnapping. Such travelers might benefit from education about how to behave as a hostage (see Chapters 43 and 90). Likewise, women traveling alone or under difficult circumstances must consider the possibility of rape and might plan on the possibility of needing emergency contraception.132 Even if statistical numbers are available for the incidence of certain illnesses or accidents during travel, it may be impossible to determine if the risk is high or low, as this may depend on the personal perception of the traveler.39
Finally, travel advisers need to understand that culture shock generated by travel to remote areas might lead to psychological breakdown, especially if a person is traveling alone or with a person with an underlying psychiatric history.39 Importantly, if travelers (prior to the trip) are made aware of, and thereby become more accepting of, poor emergency health services in many remote areas of resource-poor countries, then they or their caregivers might deal more easily with the psychological impact of a medical emergency like myocardial infarction while trekking.
Hazards of Air Travel
Modern jetliners fly very high and represent a measurable risk for cosmic ray exposure to long-haul pilots and crew. The risk to the occasional traveler, however, is negligible.26 Although the cabin is pressurized to an altitude of approximately 1524 m (5000 feet), pilots are authorized to climb to avoid weather, and the cabin altitude can effectively rise to 2438 m (8000 feet). At this altitude, everyone is slightly hypoxic; however, a patient with chronic obstructive pulmonary disease (COPD) can become dangerously hypoxic. A pulmonologist can expose the patient pre-travel to 15% oxygen and determine whether supplemental oxygen might be necessary during the flight. Planning is necessary, because airlines need several days’ notice and not all flights offer supplemental oxygen. Travelers post myocardial infarction are advised not to travel for at least 3 weeks.62,139
Medical problems during flight relate mostly to barotrauma. Flying less than 18 hours after scuba diving may increase the risk of decompression sickness.39 Transmission of respiratory pathogens like Mycobacterium tuberculosis is possible; however, air in a modern jet is high efficiency particulate absorbing (HEPA)–filtered, so risk is mostly to travelers seated nearby the infected person. Mosquitoes that might transmit diseases like malaria or dengue fever can be a problem on airliners, but such concerns are generally adequately handled by disinfection of the aircraft as it departs high-risk locations.
Symptoms of fatigue, loss of concentration, and impaired performance and sleep can occur when the normal circadian rhythm is disrupted by travel across multiple (usually five or more) times zones.26 In most persons more symptoms occur, and a longer period of adaptation is required, with travel eastward than with travel westward. With no special interventions, the typical adjustment time is 1 day per hour of time zone change. Short-acting hypnotics, timed exposure to bright light, and melatonin have been used to shorten the period of adaptation.
To avoid possible periods of amnesia associated with hypnotics,113 they are best avoided during flight and should only be used when the traveler can schedule uninterrupted sleep during the time that the drug is active. Any hypnotic (e.g., benzodiazepam, triazolam, or the non-benzodiazepam drugs zolpidem, zaleplon, and eszopiclone) should be used in the lowest effective dose. It should probably be tried prior to travel to guarantee it is well tolerated. Hypnotics are recommended to be taken for the first several nights after arrival in the new time zone and after return to the old time zone. Alcohol should be avoided because it interferes with rapid eye movement (REM) sleep.
Exposure to bright light, which suppresses melatonin production by the pineal gland, has been advocated to suppress the “left-over, wrong-time” melatonin production after arrival at the new destination. Although the general recommendation is to seek exposure to bright sunlight in the evening after westward travel and in the morning after eastward travel, recommendations become more complicated when travel exceeds eight time zones. Exposure too early to light might actually inhibit adaptation.
To facilitate adaptation, melatonin may be taken at the new bedtime after eastward travel (and in the second half of the night after westward travel) in a dose as low as 0.5 mg until one becomes adapted to the new time.78,144 In the United States, melatonin is a dietary supplement. Over-the-counter melatonin preparations may be contaminated with impurities and potency is not guaranteed. It is not available in many parts of the world and its use is not routinely advocated.108
Based on a recent review of jet lag,144 here is a summary of recommendations, depending on whether a person is traveling westward or eastward:
Deep VEIN Thrombosis
Deep vein thrombosis and its associated risk for pulmonary embolism are recognized as potential complications of flights that last for 6 or more hours.153,154 DVT occurs more commonly in those using oral contraceptives and in those with cardiovascular risk factors, active malignancy, and recent surgery.22,72,104,110 Dehydration is also an important risk factor. Pulmonary embolism is rare and occurs only in 1 to 2 travelers per million long-haul flights.95 On the other hand, up to 10% of travelers who were not using support stockings sustained asymptomatic DVT in the calf after a flight of 8 hours or longer.154
As safety permits during long-haul flights, travelers should be encouraged to move about the cabin periodically or at least isotonically exercise their calf muscles if turbulent weather forces them to remain seated. Keeping well hydrated ensures the necessity to move about the cabin in order to urinate, and avoiding alcohol helps avoid dehydration. Use of below-the-knee support stockings is encouraged. Low-molecular-weight heparin could be used in high-risk travelers with the concurrence of the traveler’s primary care physician; however, aspirin is not recommended for reduction of DVT.40
Immunizations for Travel
Immunizations may be divided into three categories: required, recommended, and routine. Vaccine schedules and booster intervals for adult travelers who are assumed to have received primary series of routine vaccines as children are given in Table 84-1.32,33,137 Vaccinations for traveling children can be found in tables referenced in the Appendix. The international traveler should have all current immunizations recorded in the WHO International Certificate of Vaccination. This yellow document is recognized worldwide and has a special page for official validation of the yellow fever vaccine. Recent copies of the document do not contain a separate page for cholera vaccine validation because the WHO officially removed cholera vaccination from the International Health Regulations in 1973. If given, cholera vaccination can be recorded in the space provided for “Other Vaccinations” in the newer booklets.
Contraindications to vaccinations are often overstated. A review of situations that are not contraindications to vaccination is included in a recent book on travel vaccinations.141 In general, live virus vaccines and attenuated bacterial vaccines are contraindicated during pregnancy and in persons with altered immunocompetence. Immune-altering conditions include underlying disease or conditions (e.g., malignancy, HIV infection, asplenia, congenital immune deficiency such as IgA deficiency) and medical therapy (e.g., corticosteroids, cancer chemotherapy, radiation therapy, immunosuppressants for organ transplantation). Although a comprehensive review of contraindications to immunizations by underlying host deficiency is beyond the scope of this chapter, a recent review of the subject is available.62 Vaccination in the HIV-infected patient is outlined in Box 84-2, which in general terms is a reasonable approach to vaccination in most immunocompromised hosts in whom live virus and live bacterial vaccines should generally be avoided.
BOX 84-2 Vaccination in HIV-Positive Adults
Required Travel Vaccines
The “required” immunizations refer not only to those regulated by the WHO but also to those required in practice. Yellow fever vaccine may be legally required for entry into some WHO member countries. Smallpox and cholera vaccines are no longer required for international travel according to WHO regulations; however, some countries continue to “require” cholera vaccine in practice. Meningococcal vaccine is required in practice by Saudi Arabia, particularly for persons arriving for the Hajj or Umrah pilgrimages.
Yellow Fever Vaccine
Yellow fever (YF) is a viral infection transmitted by mosquitoes in equatorial South America and Africa (Figure 84-1, online). The YF vaccine is a live attenuated viral vaccine that is highly protective.112,188 The YF vaccine is given as a single dose for primary immunization; the booster interval is 10 years. Because of age-related risk of encephalitis after immunization, most authorities agree that the YF vaccine is contraindicated in infants less than 6 months of age, and immunization should usually be delayed until the infant is 9 months of age or older.42 The vaccine is generally not recommended for persons who are immunocompromised or during pregnancy. If the pregnant traveler cannot avoid or postpone travel to a highly endemic area, then risk of the disease should be greater than the theoretical risk of adverse effects from the vaccine.
FIGURE 84-1 A, Yellow fever endemic zones in Africa. B, Yellow fever endemic zones in the Americas.
(From CDC Health Information for International Travel, 2009. wwwnc.cdc.gov/travel/yellowbook/2010/chapter-2/yellow-fever.aspx.)
The vaccine virus is cultured in eggs and is contraindicated in persons with a history of an anaphylactic reaction to eggs. If a person can eat eggs without a reaction, they can receive the YF vaccine.
Vaccine-associated viscerotropic disease has been reported in a small number of first-time recipients of the YF vaccine.31 Many of the subjects died with fulminant multiorgan failure. Altered thymic function or thymectomy was documented in 4 of 23 cases, and the syndrome may occur more frequently in persons older than age 60 years; however, the small number of cases makes accurate risk factor assessment impossible.13 The disease is felt to be an infection by the attenuated vaccine strain facilitated by an altered host response rather than a change in virulence of the vaccine strain. Persons who have successfully received a first dose of YF vaccine are unlikely to be at risk with a booster dose if they have remained immunocompetent hosts.
Although YF vaccine-associated viscerotropic disease is rare (approximately one event per 250,000 to 350,000 doses), the potentially deadly outcome prompts careful risk assessment, especially when considering first-time vaccination in elder travelers. Some countries may be listed as endemic for YF, but certain locations within the country may pose no risk. If a person for whom the vaccine is contraindicated (or ill-advised because the person is not truly at risk) must travel to a country where yellow fever vaccine is required for entry, then according to WHO regulations a signed statement indicating that the YF vaccine could not be given because of medical contraindications should be acceptable in lieu of documented vaccination. The statement should be written, if feasible, on letterhead stationery and accompanied by authoritative stamps or seals. Contacting the embassy or consulate of the country may be necessary to help guarantee that the letter of waiver will be accepted.
The injectable cholera vaccine is not highly efficacious, even when the primary series of two doses given a week or more apart is received.142 The WHO no longer endorses a requirement for this vaccine for entry into any country. For countries that might still require cholera vaccination for travelers arriving from cholera-endemic areas, recording a single cholera dose in the traveler’s International Certificate of Vaccination should suffice to meet this requirement.
Travelers going to areas endemic or epidemic for cholera are encouraged to follow food and water precautions gauged to prevent all forms of travel-associated diarrhea. Oral killed and live-attenuated vaccines133 are available in some countries, but at present, there are no standardized recommendations for use of cholera vaccines, although health care workers and relief workers going to outbreak areas might be suitable candidates. Likewise, travelers to cholera-endemic areas, who are achlorhydric or have had a partial gastric resection, are logical candidates for cholera vaccine.
The requirement for smallpox vaccine for international travel was removed from the WHO regulations in 1982. The CDC has embarked on an initiative to immunize health care providers, first responders, and others involved in bioterrorism preparedness, but the vaccine is not otherwise available and travel is not considered a sufficient reason for vaccination.109
Recommended Travel Vaccines
Recommended vaccines are those that are not routinely given during childhood in the United States, but are advised for travelers based on their travel health risk assessment. Vaccines in this category include those for hepatitis A and B, typhoid fever, meningococcal meningitis, Japanese encephalitis virus, rabies, tick-borne encephalitis, varicella zoster virus (VZV), influenza, and bacillus Calmette-Guérin (BCG). Some vaccines have become routine in children (e.g., hepatitis B since 1991, and hepatitis A more recently in the United States),7 so in the future, more travelers will have been vaccinated. Likewise, more travelers will already have received meningococcal vaccine as adolescents or young adults for entry into institutions of higher education or as 11- to 12-year-olds, for whom the vaccine is now routinely recommended. Arguably, VZV vaccine should be used routinely in the United States, but for many adult U.S. travelers, it remains a vaccine that must be added. Influenza vaccine is often but not routinely used in children; each year it is recommended for many travelers. Although BCG vaccination is used in children in the developing world, it is not used in U.S. children.
Hepatitis A Vaccine
Hepatitis A virus (HAV) infection is the most common vaccine-preventable disease in international travelers to the developing world.165,187 In the absence of vaccination, HAV infection occurs in 1 to 10 persons per 1000 travelers at risk during 2 to 3 weeks of travel. Risk is high even among those residing in “first class” accommodations. Adventure travelers who venture off usual tourist routes may be at increased risk compared with other groups of travelers. Although HAV infection is asymptomatic in young children and self-limited in most adults, it causes greater than 2% mortality in infected adults older than age 40 years, considerable morbidity during travel, and lost productivity after travel. Vaccination against HAV should be considered for all travelers to regions where sanitation and hygiene are poor.
Individuals with a history of jaundice, who were born prior to the 1950s, or who were born or resided for lengthy periods in endemic regions are likely to have natural immunity to HAV.173 They should be screened for IgG antibodies against HAV, because if these are present, it is possible to avoid the cost of vaccination, which is usually more expensive than serologic testing. However, because vaccination of HAV-immune persons is not associated with adverse consequences, a traveler who does not have time prior to departure to receive the testing results should be vaccinated.
A single dose of monovalent hepatitis A vaccine affords adequate protection by 7 to 10 days following vaccination.47,178 Amelioration of HAV clinical infection occurs if serum immune globulin is administered up to 14 days after exposure to HAV. HAV challenge experiments in a simian model and indirect evidence in humans suggest that immunization with monovalent vaccine immediately prior to travel obviates the need for serum immune globulin.47,165 Some authorities continue to advocate a dose of serum immune globulin if HAV vaccination cannot be given sooner than 2 weeks before travel. Others feel ISG is seldom indicated except in immunocompromised persons who might not respond to the hepatitis A vaccine.47
HAV vaccine products are thought to be interchangeable. After two full doses separated by 6 to 12 months, protection is likely life long, so booster doses are not recommended in immunocompetent travelers.178 Travelers who fail to receive their second dose of HAV vaccine within 6 to 12 months should simply receive one full dose of monovalent vaccine with the anticipation of life-long immunity. Protective antibody levels have been produced even when second doses were given 8 years after the first dose.86
Hepatitis B Vaccine
Hepatitis B vaccine was added to the list of vaccines recommended for routine immunization of children in the United States in 1991, and consideration should be given to vaccinating all U.S. adults regardless of travel. Risk to short-term travelers is low; however, travelers should be vaccinated when they might have contact with body fluids or blood (e.g., through sex or medical work), when they anticipate receiving medical care in a developing country or when they are frequent short-term travelers. Long-term travelers and expatriates should be vaccinated.85
Two recombinant vaccines are available and are thought to be interchangeable. The standard regimen for both vaccines is doses at 0, 1, and 6 months. One of them, Engerix-B, is FDA approved for an accelerated dosage schedule of 0, 1, and 2 months with a booster dose at 12 months for long-lasting protection. Although a highly accelerated 3-week schedule is not approved, literature supports dosing at 0, 7, and 21 days with a 12-month booster.25,103 This regimen affords 65% protection at the end of 1 month and is an attractive option for at-risk travelers who plan to depart in the next 3 to 4 weeks.
A combined hepatitis A and hepatitis B vaccine is now available and is dosed at 0, 1, and 6 months. Because a smaller dose of HAV antigen is used in this preparation, travelers must receive their second dose prior to travel for reliable protection. Literature also supports a highly accelerated 3-week dosing regimen with a 12-month booster.121
After any of the HBV vaccination regimens, additional boosters are not recommended for normal hosts. A protective amnestic response after exposure to wild-type virus can be expected even after serum concentrations of antibody have fallen to undetectable levels. An interrupted hepatitis A or B vaccine series can be completed without restarting.
Typhoid Fever Vaccine
The incidence of typhoid fever among American travelers is relatively low (1 to 10 cases per 100,000 travelers, in contrast to >100 cases per 100,000 native population in certain parts of the Indian subcontinent130); but among reported cases in the United States, the majority were acquired during international travel.99,111 Risk is highest among visitors to the Indian subcontinent and particularly high among those visiting friends and relatives. Visitors to Central and South America, Africa, and Asia should be considered for typhoid vaccination when they might be exposed to conditions of poor sanitation and hygiene, even for short periods of time.48,169
Increasing antibiotic resistance among Salmonella enterica serotype Typhi is another reason to be vaccinated.1,16 However, the current vaccines afford only 50% to 70% protection, and emergence of S. enterica serotype Paratyphi, against which protection is not afforded by the current vaccines, underscores the importance of hygienic food and beverage choices among travelers.61
Two vaccines are currently available and offer a similar degree of protection. The parenteral purified Vi polysaccharide typhoid vaccine is administered as a single injection with a booster recommended every 2 years. The oral Ty21a typhoid vaccine uses a live-attenuated strain of S. enterica serotype Typhi. One capsule is taken every other day for four doses (three doses in Europe).19 A booster regimen is recommended every 5 years.
Vaccine protection against meningococcal meningitis is recommended for long-term travelers to the sub-Saharan “meningitis belt” (Figure 84-2, online).7,38,138 Short-term travelers to this region should receive vaccine if they will travel during the dry season (December to June) or have extensive contact with local people. Meningococcal vaccine is required for travel to Saudi Arabia during the time of the annual Hajj and Umrah religious pilgrimages. Regardless of travel, the classic recommendation has been that young adults who will live in school dormitories, those with complement deficiencies, those who will have prolonged contact with a local population such as in a refugee camp, and persons with surgical or functional asplenia should be vaccinated. Travelers to regions where outbreaks are occurring should be vaccinated. Practitioners who do not subscribe to commercial information services that are routinely updated should check the CDC website (www.cdc.gov/travel) periodically to determine where epidemic disease is occurring.
FIGURE 84-2 Meningitis belt. Consult details in the CDC Yellow Book for locations within each country where, and seasons when, pretravel vaccination is recommended.
(From CDC Health Information for International Travel, 2009. wwwnc.cdc.gov/travel/yellowbook/2010/chapter-2/meningococcal-disease.aspx.)
The quadrivalent meningococcal polysaccharide vaccine induces immunity against serogroups A, C, Y, and W-135. A single dose appears to provide immunity for 5 years. A single-dose quadrivalent meningococcal polysaccharide-protein conjugate vaccine is the preferred vaccine for age group >2 years, with a booster recommended every 5 years45 for ongoing risk. However, neither vaccine provides immunity against serogroup B.
Travelers who had previously been vaccinated with polysaccharide vaccine and need revaccination should receive conjugate vaccine.
Japanese Encephalitis Virus Vaccine
Japanese encephalitis ( JE) is a mosquito-transmitted viral infection prevalent in Asia and Southeast Asia. Transmission is year round in tropical and subtropical areas and during the late spring, summer, and early fall in temperate climates. JE virus is not considered a risk for short-term travelers visiting the usual tourist destinations in urban and developed resort areas.28
Risk of infection can be greatly decreased by personal protective measures that prevent mosquito bites. For visitors to rural areas during the transmission season, the estimated risk for JE during a 1-month period is 1 : 5000, so vaccination should probably be offered to both long- and short-term visitors to rural areas during transmission season, particularly when mosquito exposure might be intense and rice and pig farming occurs nearby.
The standard schedule for the inactivated viral vaccine (mouse brain preparation) has been doses injected at 0, 7, and 30 days. An accelerated schedule of doses at 0, 7, and 14 days results in a lower rate of seroconversion. When risk of exposure continues, a booster dose of vaccine may be given every 2 to 3 years.
Adverse reactions to the mouse brain preparation of JE vaccine include local pain and swelling at the injection site in about 20% of recipients, systemic symptoms (fever, headache, malaise, rash) in about 10%, and hypersensitivity reactions at a rate of 0.1 to 5 per 1000 administrations.23 The hypersensitivity reactions can rarely be fatal and may occur immediately or with delays of up to 2 weeks. Limited data suggest that persons who have had urticarial reactions to hymenopteran envenomation and to other stimuli might be at greater risk of JE vaccine–induced hypersensitivity reactions. JE vaccine recipients should be directly observed for 30 minutes after injection and should not travel until 10 days after their last dose because of the risk of delayed adverse reactions. A recently approved non–mouse brain vaccine appears considerably safer and as effective as the older vaccine50 This new vaccine requires only 2 doses, but in the United States is restricted to adults older than age 17 years.
Rabies Vaccine (see Chapter 60)
Although rabies is endemic in much of the world, the risk of rabies for most travelers is very low.185 Avoidance of dog bites eliminates much of the risk.29 Other animal species important to the transmission of rabies to travelers include monkeys, mongooses, bats, and foxes. Preexposure rabies immunization should be considered for rural travelers, particularly adventure travelers who go to remote areas, persons with occupational (veterinarians) or recreational (spelunkers) exposure, and for expatriate workers, missionaries, and their families living in countries in which rabies is a recognized risk. Children should be targeted for preexposure vaccination in high-risk regions, because they may not tell their parents when they have been bitten or exposed to the rabies virus.
Any of the three tissue culture–derived inactivated virus rabies vaccines can be administered intramuscularly in the deltoid (not gluteal) muscle in a preexposure schedule of 0, 7, and 21 or 28 days.29 For persons who continue to be at risk of exposure, a booster can be given every two years, or less frequently based on annual serology testing. In the event of an exposure, the vaccinated traveler must understand how to clean the wound thoroughly and immediately seek two additional doses of vaccine. Preexposure vaccination obviates the need for postexposure administration of rabies immune globulin (RIG), which is an important consideration because RIG may be very difficult to obtain.92,131 Persons who are exposed without having had preexposure rabies vaccination require both RIG and a four-dose course of rabies vaccine given over 14 days, instead of 5 doses over 28 days, as recently recommended by the U.S. Advisory Committee on Immunization Practice.3 Persons with immunosuppression should still receive the five doses of the vaccine.7 Intradermal (ID) administration results in slightly lower and shorter-lasting protection, so it is not routinely recommended. Also, chloroquine impairs the immune response, so an ID-administered preexposure series should be completed well before chloroquine prophylaxis begins. Cell culture rabies vaccine available outside the United States, unlike neural tissue vaccines that have serious side effects, are acceptable alternatives.153
Mild local reactions to rabies vaccine occur in about 20% of vaccinations and are self-limited over 1 to 3 days. Up to 10% of recipients may develop mild fever, myalgia, headache, dizziness, or gastrointestinal upset. Much less commonly, allergic reactions characterized by urticaria, angioedema and respiratory symptoms can develop with serum sickness-like syndrome possible after doses of human diploid cell–derived vaccine. Sudden death and encephalomyelitis are rare.