Because the spectrum of infectious diseases changes with time and location, travelers to or between foreign countries should be aware of the necessity for immunizations. The Centers for Disease Control and Prevention (CDC) has a comprehensive traveler’s health website at wwwn.cdc.gov/travel/default.aspx.
A detailed, updated list of required immunizations by country can be obtained in the publication Health Information for International Travel (CDC), also known as the “Yellow Book.” The CDC Internet site, with links to the online copy of the Yellow Book and instructions for ordering a hard copy, is wwwn.cdc.gov/travel/contentYellowBook.aspx.
Vaccinations may be given under the supervision of any licensed physician. All travelers should carry a completed International Certificate of Vaccination with proper signature and validation for all vaccinations administered. Yellow fever and cholera vaccinations must be officially recorded and stamped. Failure to secure validation at an authorized city, county, or state health department renders the certificate invalid, and may force you to be revaccinated or quarantined.
It is extremely important to plan immunizations as far in advance of an expedition as possible, since some vaccines interact in ways that diminish effectiveness. For instance, yellow fever and cholera vaccines need to be given either on the same day or at least 3 weeks apart.
TETANUS
Everyone should be properly immunized against tetanus, which is caused by the bacterium Clostridium tetani. In the United States, diphtheria-tetanus-pertussis (DTAP) vaccine is given as an intramuscular injection at ages 2, 4, 6, and 8 months, followed by a booster at age 4 to 6 years, usually before entry into school. These shots provide immunity from tetanus, as well as from diphtheria and pertussis (whooping cough), for about 10 years. The first booster shot is usually given at age 11 or 12 years in the form of Tdap vaccine. Thereafter, Td (tetanus and diphtheria) vaccine is recommended at 10-year intervals. However, given a resurgence of whooping cough seen in adults, the recommendation may change to continue immunizing against pertussis with the Tdap vaccine in perpetuity. Following immunization against tetanus, immunity in any individual is unknown, and can be determined by measuring antibodies in blood. This is particularly important in elders, in whom the immune response to vaccination may be suppressed by a general lower level of the immune system associated with age.
Here are the vaccines that are licensed as of this writing for different age-groups:
1. Tdap (tetanus, diphtheria, pertussis): Adacel (Sanofi Pasteur) ages 11 to 64 years; Boostrix (GlaxoSmithKline) ages 10 to 18 years
2. DTaP (diphtheria, tetanus, pertussis): Daptacel (Sanofi Pasteur) ages 6 weeks to 7 years; Tripedia (Sanofi Pasteur) ages 6 weeks to 7 years; Infanrix (GlaxoSmithKline) ages 6 weeks to 7 years; Pediarix (GlaxoSmithKline) ages 6 weeks to 7 years
3. Td (tetanus, diphtheria): Td (Sanofi Pasteur) ages 7 years and older
One obvious question is, “Which vaccine should be used for children between ages 7 years and 10 years?” It is probably best to use the DTaP vaccine for this age-group, even though no vaccine is licensed for this age-group, and either Tdap or DTaP would likely induce the proper immunities.
The current practice is to take a booster shot (Td) if one sustains a “dirty” wound, deep puncture, serious burn, significant crush injury, or similar injury and has not had a tetanus shot in the preceding 5 years. If a wound is believed to be at particularly high risk for infection with C. tetani (e.g., if it is a very deep puncture or contaminated by soil or animal feces), it may also be recommended to have an injection of tetanus immune globulin, as well as a tetanus booster immunization. Whether or not to administer tetanus immune globulin is generally a judgment call by the treating health care professional. The immune globulin contains actual antibodies against the bacteria, so that the recipient carries protective antibodies against the bacteria until his or her body has a chance to manufacture its own antibodies in response to the Td booster shot.
Any traveler who will be away from medical care for more than 48 hours should have adequate tetanus immunization. The recommendations are as follows:
1. A person previously immunized should receive a booster dose of tetanus toxoid if his last dose was not administered within the past 10 years. A dose of Tdap vaccine (tetanus, diphtheria, and pertussis) may be administered if pertussis is a concern. Diphtheria immunization is usually boosted simultaneously. If there is a good chance that the traveler will suffer an injury during the trip, he should take a booster if the last dose was not administered within the past 5 years.
2. Nonimmunized individuals should become immunized with a series of three injections (this requires 3 to 6 months).
Low-risk (for tetanus infection) wounds are those that are recent (less than 6 hours old), simple (linear), superficial (less than ½ in, or 1.3 cm, deep), cut with a sharp edge (knife or glass), without signs of infection, and free of contamination with dirt, soil, or body secretions. High-risk wounds are those that are old (greater than 6 hours), crushed or gouged, deep (greater than ½ in deep), burns, frostbite, with signs of infection, and contaminated. If someone suffers a wound, here are standard recommendations:
|
Victim |
Low-Risk Wound (not heavily contaminated) |
Contaminated Wound (tetanus-prone) |
|
Never Immunized |
Tetanus toxoid Tetanus immune globulin |
Tetanus toxoid Tetanus immune globulin |
|
Immunized |
||
|
Last booster within 5 yr |
No shot |
No shot |
|
Last booster within 10 yr |
No shot |
Tetanus toxoid Tetanus immune globulin |
|
Last booster over 10 yr |
Tetanus toxoid |
Tetanus toxoid Tetanus immune globulin |
POLIOVIRUS; DIPHTHERIA; PERTUSSIS (WHOOPING COUGH); MEASLES, MUMPS, RUBELLA (GERMAN MEASLES); CHICKENPOX; HAEMOPHILUS B; ROTAVIRUS
Immunization against poliomyelitis, diphtheria, pertussis, measles, mumps, and rubella should be obtained before travel. These are routinely administered during childhood in the United States. Because of the incidence of these infectious diseases in developing countries, such immunizations are mandatory before travel. Immunizations against Haemophilus type b (which causes middle ear infections and meningitis) and the virus that causes chickenpox are available, and should be considered under recommendation from your physician. Measles vaccine should be given to any person born after 1956 who has not received a prior booster dose. Mumps (a viral infection) is making a comeback in the United States and other countries because of failure to vaccinate. It is not a trivial disease, particularly in adults, and is highly communicable. In children, mumps typically causes fever, headache, muscle aching, fatigue, loss of appetite, and swelling of salivary glands, in particular the parotid glands, which are located in the cheeks directly in front of the ears. In adults, complications of mumps may include inflammation of brain, meningitis, swollen and painful inflamed testicles, ovarian or breast inflammation, miscarriage, and deafness.
Polio is still present in developing nations (e.g., sub-Saharan Africa, India, Nepal, Indonesia, Pakistan). Unimmunized adults (age greater than 18 years) should receive a series of three injections of the inactivated (virus) Salk vaccine, not the oral (Sabin) vaccine, which is recommended for children. Those under 18 who have never been immunized should receive three doses of oral polio vaccine 1 month apart. People who travel to high-risk areas (e.g., outside the Western Hemisphere) who were immunized as children should receive one booster dose of oral polio vaccine or an injection of e-IPV polio vaccine.
Two adolescent/adult formulations of pertussis vaccine are combined with diphtheria and tetanus toxoids (Tdap): Boostrix (approved for ages 10 to 18 years) and Adacel (approved for ages 11 to 64 years). One of these should be given instead of standard tetanus-diptheria vaccine if pertussis is a concern.
RotaTeq is an oral vaccine given in a three-dose series recommended for infants to prevent the gastrointestinal illness caused by rotavirus. Rotarix is given in two doses. It is advised that children who have had an episode of intussusception not receive these vaccines.
SMALLPOX
The last reported case of endemic smallpox (caused by the Variola virus) was in Somalia in 1977. Therefore, smallpox immunization is no longer required for international travel, and the vaccine is not commercially available. However, there is a chance that isolated cases still occur (without reporting) in India, the Himalayas, and equatorial Africa. Travelers to these areas should inquire about the latest recommendations from the CDC in Atlanta.
Because smallpox has been suggested as an agent of bioterrorism, a brief description of infection for the purpose of recognition follows. The virus enters a human through the respiratory tract. It incubates and multiplies for 7 to 17 days, after which the victim abruptly develops severe headache, backache, and fever. The mouth, tongue, and throat may show lesions before the onset of the rash on the skin, which begins as small red spots and bumps that become blisters over a few days. Usually, the rash appears first on the face and limbs, and then appears on the torso. The blisters may appear pus-filled with depressed centers and take a week to dry and form a crust. As opposed to chickenpox, where the skin lesions are in various stages of development, all the lesions of smallpox are in the same stage of development. With chickenpox, the fever accompanies the onset of the rash, and the rash is more concentrated on the torso, rather than the limbs.
Smallpox vaccine can be effective if administered before exposure or early enough in the incubation period.
Monkeypox, which along with smallpox is an “orthopox,” is endemic to forested areas of western and central Africa, but does not as yet pose a significant public health risk; there is no vaccine against the causative agent. It has been reported to be present in southern Sudan.
CHOLERA
Cholera is an intestinal infection caused by 2 serogroups (01 and 0139) of the microorganism Vibrio cholerae, either of which induces painful diarrhea and extreme fluid losses through the gastrointestinal tract. Cholera can reach epidemic proportions. It is estimated that 4 out of every 100 persons who acquire the illness die. A person whose stomach contains normal gastric acid is not at much risk for acquiring cholera. No country currently requires immunization, and the CDC does not recommend cholera vaccination for travel. However, some localities require proof of cholera immunization for travelers entering from a territory that still reports the disease. For this purpose, documentation of a single dose of oral vaccine (not available in the United States) generally is sufficient. The only vaccine available is a killed whole-cell vaccine. It is likely that as vaccines become less expensive, they will be used more often in areas where the infection is endemic.
YELLOW FEVER
Yellow fever is acquired in tropical (sub-Saharan) Africa and tropical South America, where victims may suffer the bite of the Aedes aegypti mosquito (urban environment) or other mosquitoes (jungle environment). Immunization is effective in preventing the disease; a single 0.5 mL subcutaneous injection of 17-D-204 strain YF-VAX (Aventis) is administered and immunity is acquired after a 10-day waiting period. The vaccine is good for 10 years, after which time a booster is required to maintain immunity. Infants younger than 9 months and pregnant women should not be routinely immunized, unless they are at high risk for contracting the disease. It is also contraindicated in people with immunosuppression (such as human immunodeficiency virus [HIV] infection) or with an allergy to eggs. Yellow fever vaccinations must be given at an officially designated Yellow Fever Vaccination Center, and the certificate validated at the same center. The vaccine is not required for travel from the United States into Canada, Mexico, Europe, or Caribbean countries, but should be considered for travel into the province of Darien in Panama. The CDC travel Internet site should be consulted for the latest information on recommendations. To be maximally effective, cholera and yellow fever vaccines should be administered either at the same time or at least 3 weeks apart. A rare side effect of yellow fever vaccination is a severe reaction with symptoms similar to those of yellow fever. This may occur in 1 in 50,000 elderly (greater than 65 years old) recipients. An exemption (from vaccination) letter from a doctor acceptable to the customs officials of a destination country may allow a person to skip the immunization requirement.
MENINGOCOCCUS
The meningococcus is a bacterium (Neisseria meningitidis) that can cause meningitis, particularly in children and young adults. It is a wise idea for travelers to Nepal—particularly hikers and backpackers—to be immunized. Certain areas of sub-Saharan Africa are also considered high risk from December to June. Vaccination against meningococcal disease is not a requirement for travel to any country except Saudi Arabia, where travelers to Mecca during the annual Hajj and Umrah pilgrimage must have proof of vaccination. Menactra, a tetravalent meningococcal polysaccharide-protein conjugate vaccine (MCV4), provides protection against serogroups A, C, Y, and W-135 of the bacteria, and is given in one subcutaneous injection; protection for 5 years is achieved 1 to 2 weeks after administration. It is approved for persons ages 2 to 55 years. The vaccine is now recommended for children aged 11 to 12 years in the United States at their regular health care visit, and if at all possible before entry into college. The vaccine previously recommended by the CDC is Menomune, a tetravalent meningococcal polysaccharide vaccine (MPSV4) that is still available and is believed to be somewhat less effective. It is recommended for persons older than 55 years, or at any age if MCV4 is not available. The vaccines are believed to provide immunity for 5 years when administered at age 4 years or older. If someone has not been immunized and comes in close contact with a person known to have meningococcal disease, antibiotics can be prescribed within 14 days of exposure for 3 days to prevent or minimize the spread of the disease. The recommended antibiotics are rifampin for children and adults, ciprofloxacin for adults, or ceftriaxone (injection) for children and adults. Azithromycin in a single 500 mg dose is also likely effective.
HERPES ZOSTER
Zostavax is a new vaccine to reduce the risk for herpes zoster in adults ages 60 years and older. It is given in a dose of 0.65 mL one time subcutaneously. Because it contains live attenuated virus, it should not be given to anyone who is immunosuppressed for any reason. It is given as a single dose subcutaneously. It appears to be quite effective in preventing shingles in persons who have never before suffered from this condition.
HUMAN PAPILLOMAVIRUS
A vaccine (Gardasil [quadrivalent human papillomavirus types 5, 11, 15, 18 recombinant]) is approved to prevent infection with human papillomavirus in females ages 10 to 26 years. The vaccine is administered in three doses at 0, 2, and 6 months, intended to prevent infection that might lead to later development of cervical cancer.
HEPATITIS
A recombinant DNA vaccine (Recombivax, not derived from human plasma) for immunization against viral hepatitis type B is recommended for travelers to underdeveloped countries. A series of three injections requires 6 months to complete. Another recombinant vaccine is Engerix-B, which can be given on an accelerated schedule over 2 months. If a person has not been immunized against hepatitis type B and is exposed to the virus (e.g., by a needle stick), he may require an injection of hepatitis B immune globulin to provide short-term protection until immunity can be acquired from the DNA vaccine.
Hepatitis A virus is spread through contamination of water and food, and is often encountered in developing nations and areas of poor hygiene. Hepatitis A vaccine (Vaqta), inactivated, is available. It is administered intramuscularly to those age 2 years or older at least 2 weeks before exposure to hepatitis A virus. The dose is 0.5 mL (25 units) up to age of 18 years, and 1 mL (50 units) in people older than 18 years. It is given in a series of two injections. Havrix is a similar vaccine. Twinrix is a combination vaccine (hepatitis A and B) given to persons age 18 years and older in a 1.0 mL dose in a three-injection series at 0, 1, and 6 months. In an alternative dosing regimen, it can be given at day 0, day 7, a day chosen between days 21 to 28, and at 1 year (booster).
Pooled immune serum globulin (ISG, or gamma globulin) can be administered to prevent or diminish the effects of viral hepatitis type A in unimmunized people. The administration of ISG interferes with the antibody response stimulated by other live-virus vaccines, so it should be administered 2 to 4 weeks after any other vaccines. Because the effects of ISG disappear after 6 months, it should be administered just before the trip, and at appropriate booster intervals during prolonged travel in endemic areas. It should be administered in the event that someone has been given his or her first dose of hepatitis A vaccine, but a period of less than 2 weeks has elapsed after injection and before risky travel.
BUBONIC PLAGUE
A preexposure vaccine is available for immunization against bubonic plague caused by Yersinia pestis. This is administered only to people whose travels or occupations place them at high risk. In most countries where plague is reported, the risk is greatest in rural mountain or upland regions. Vaccination is generally considered for those who will reside in regions where plague is endemic, and where avoidance of rodents and fleas is impossible. The vaccine is injected in two doses 1 month apart, followed by a booster dose after 6 months.
RABIES
Preexposure and postexposure rabies vaccinations are discussed on page 410.
MALARIA
Malaria is discussed on page 146.
TYPHOID FEVER
Typhim Vi polysaccharide vaccine is available for immunization against typhoid fever caused by Salmonella typhi. Immunization is recommended for travelers who visit countries (e.g., Cambodia, Nepal, South Africa, Indonesia, and many others) known to harbor the disease, and for persons with adventurous dietary habits. A single intramuscular injection is required, followed by booster injection at 2-year intervals, depending on the local disease risk. An oral vaccine (Vivotif Typhoid Vaccine Live Oral Ty21a, Berna Products) is given as one capsule every other day for four doses in people age 6 years or older. A booster series is necessary every 5 years. The oral vaccine regimen should be completed at least 7 days before travel. Capsules, which should be kept refrigerated, should be swallowed (not chewed) with cool or lukewarm water on an empty stomach and without concomitant alcohol within 2 hours of ingestion. Side effects, which include fever, headache, and flu-like symptoms, are more commonly associated with the injections. Gastroenteric symptoms may be associated with the oral vaccine.
TYPHUS FEVER
Typhus vaccine is no longer available in the United States, and, is not recommended for the foreign traveler.
INFLUENZA
Influenza vaccine is administered in one or two injections to children and adults in October and November (in the Northern Hemisphere) before the flu season (December through March), with a maximum duration of effect of 6 months. It is approved for use in persons ages 6 months and older. Persons 3 years of age or older should receive a single intramuscular injection of 0.5 mL. Children 6 to 35 months of age should receive only 0.25 mL. Children younger than 9 years of age who have never been immunized should receive two doses spaced at least 4 weeks apart.
Vaccination of high-risk people (older than 65 years or with chronic illness) before flu season is essential. Persons for whom annual vaccination is recommended include the following:
• All persons who wish to reduce the risk of becoming ill with influenza or transmitting the disease to others
• Children ages 6 months to 4 years
• All persons ages 50 years or greater
• Children and adolescents ages 6 month to 18 years receiving long-term aspirin therapy who might be at risk for experiencing Reye syndrome
• Women who will be pregnant during influenza season
• Adults and children who have immunosuppression caused by medications or HIV
• Adults and children who have chronic pulmonary (including asthma), cardiovascular (except hypertension), kidney, liver, blood, or metabolic (including diabetes) disorders
• Adults and children with any condition that might compromise respiratory function
• Health care personnel
Each year, the vaccine contains the influenza virus strains that are believed to be most prevalent in the United States. Inactivated (killed-virus) influenza vaccine should not be given to those who are sensitive to egg products. “Whole” vaccines should not be given to children under age 13 years. Children should be given “split” vaccines, which have been chemically treated to reduce adverse reactions.
A live, attenuated nasal spray vaccine (FluMist) is at least as effective as injected vaccine, and is approved for persons ages 5 to 49 years who are free of chronic illnesses. It is administered as a spray of 0.25 mL into each nostril (0.5 mL total dose). Children ages 5 to 8 years old who have not been previously immunized should receive two doses spaced at least 6 weeks apart. FluMist should not be administered to family members or close contacts of immunosuppressed persons requiring a protected environment.
Amantadine hydrochloride (Symmetrel) and rimantadine are prescription oral drugs that interfere with viral uncoating within living cells and are moderately effective in preventing influenza A. However, because they confer no protection against influenza B, they are not considered substitutes for appropriate immunization.
Oseltamivir phosphate (Tamiflu) is an antiflu pill given in a dose of 75 mg twice a day for adults. Zanamivir (Relenza) is a similar drug administered in a dose of 2 inhalations twice daily. These drugs interfere with the release of newly formed influenza virus from host cells and can be used to both prevent and treat influenza A and B.
PNEUMOCOCCAL PNEUMONIA
A polyvalent pneumococcal polysaccharide vaccine is available against pneumonia caused by Streptococcus pneumoniae (pneumococcus). In general, this vaccine is recommended for elderly (over 65 years) or infirm (those with cancer or with chronic heart, kidney, liver, or lung disease; people without a spleen; alcoholics; diabetics; those with sickle cell anemia) travelers who would be debilitated by a bout of pneumonia. The vaccine is not routinely recommended for children.
JAPANESE ENCEPHALITIS
Japanese encephalitis is a viral disease transmitted predominantly by Culex mosquitoes in South Asia, Southeast Asia, and the Asian Pacific Rim. Wind-blown mosquitoes have perhaps spread the virus from Papua New Guinea to the Australian mainland. The victim first suffers a mild, nonspecific viral illness accompanied by fever and headache. Most infections remain mild. However, in an extremely small number of cases, the victim goes on to develop severe meningoencephalitis, characterized by headache, weakness, fatigue, fever, confusion, seizures, paralysis, and altered mental status. There is no specific therapy beyond supportive care. From 20% to 30% of victims die.
Travelers for more than 1 month to tropical Asia, particularly into rural rice-growing settings, are candidates for Japanese B encephalitis vaccine, which is given in a series of three injections over 2 weeks to 1 month. A booster dose may be given after 2 to 3 years. The current vaccine may cause side effects that may not occur until a week after the final injection, so it is recommended that travel not occur until at least that time has elapsed. Newer inactivated and live attentuated vaccines are becoming available.
LYME DISEASE
See page 157.
PHYSICIANS ABROAD
A traveler to a foreign country may become ill enough to require the services of a physician. The International Association for Medical Assistance to Travellers (IAMAT) is a nonprofit organization that provides a list of approved doctors who adhere to international standards, which include standard fees. IAMAT also distributes, free of charge, updated material on immunization requirements, malaria and other tropical diseases, and sanitary (food and water) and climatic conditions around the world. The directory of affiliated institutions can be obtained by calling or writing to IAMAT in Ontario, Canada. Other international medical assistance and rescue programs include the following (since specific street addresses and phone numbers are constantly changing, check with directory assistance):
• Air Ambulance Network, Inc., Tarpon Springs, Florida
• Divers Alert Network, Duke University Medical Center, Durham, North Carolina
• Global Emergency Medical Service, Alpharetta, Georgia
• Global Rescue, Boston, Massachusetts
• International SOS Assistance, Philadelphia, Pennsylvania
• Medex Assistance Corporation, Baltimore, Maryland
• Travel Assistance International, Millersville, Maryland