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Chapter 3 Vaccines for Travel |
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Key Points
What's New
Being up-to-date on your “shots,” or completing a vaccination (immunization) schedule before departure, is one of the most important steps you can take to prevent a travel-related disease. Immunizing travelers, however, has become increasingly complex because new vaccines (e.g., Menactra, for meningitis; Dukoral for travelers’ diarrhea and cholera) are being brought to market, whereas others (e.g., injectable cholera) are being phased out. In the meantime, new diseases for which vaccines are not yet available, such as SARS and avian influenza, have emerged. Travelers may complicate the situation by not allowing enough time to be immunized according to established vaccination schedules or requirements. Of course, in some cases, their departures may be unscheduled, perhaps for business or personal reasons. Although some vaccines, such as the combined hepatitis A and B vaccine (Twinrix®), may be administered in an accelerated schedule over 3 weeks, some travelers may be forced to delay their trip, or forgo essential protection, if they are scheduled to depart on short notice. Therefore, travelers planning an itinerary should seek pre-travel health advice 6 to 8 weeks before departure to be sure there is enough time for multiple doses of one or more vaccines, if these are needed. Business travelers, or others, who have unpredictable schedules, should have their travel immunizations updated regularly to ensure that they are prepared for last minute travel, regardless of the destination. Planning VaccinationsVaccination recommendations are determined by a host of factors:
The standard approach to travel immunization is to consider the “3 Rs:” (1) Routine, (2) Required, and (3) Recommended.
Travel medicine advisors carry out an individual risk assessment for each client in these three areas of immunization, taking into consideration the factors discussed above. A risk management program of immunization is then constructed to meet the needs, time available before departure, and financial resources of the traveler. Vaccines for routine use and specialized vaccines for international travel are described subsequently. Table 3.2 contains specific information on dosing schedules, indications, booster doses, and precautions. Table 3.3 contains immunization guidelines in HIV-infected travelers. Childhood immunization schedules for the United States are found in Figure 3.2. Immunization during pregnancy is discussed in Chapter 20. Checking Your Routine ImmunizationsVaccination Schedules for 2008 Recommended Immunization Schedules for Persons Aged 0-18 Years Recommended Adult Immunization Schedules
Vaccine and Disease SummaryChickenpox (VaricellaChickenpox is a viral infection caused by Varicella zoster. It is highly contagious and usually quite mild, although serious complications, even fatalities, may result, especially when the infection occurs in an adult. It is primarily a disease of children; in North America 90% of children will have been infected or vaccinated by age 10. New immigrants from Latin America and South Asia should be tested for varicella antibodies if the history of infection is unknown because in these areas of the world chickenpox tends to occur at an older age. The infection is spread by contact with infected objects and the respiratory route when there is close contact with an infected person. Those who have had this disease have lifelong immunity and do not need the vaccine prior to travel Note: A high-dose, live varicella vaccine (Zostavax) has recently been marketed by Merck for adults over age 60. This vaccine is indicated for those who have had chickenpox in the past but who have the potential to develop shingles ( a reactivation of chickenpox virus in nerves of the spinal cord or brain) in later life as a consequence of waning immunity against the varicella virus This vaccine should not be confused with the vaccine used to prevent chickenpox. Chickenpox vaccine is now a routine immunization for all children in the United States. All children should receive two doses of varicella vaccine; one dose of chickenpox vaccine between 12 and 15 months and a second dose at age 4-6 years. Adults and adolescents 13 years of age or older should receive two doses of the vaccine, 4 to 8 weeks apart. Chickenpox vaccine, which is a live virus vaccine, should not be given during pregnancy, and female patients should not become pregnant for at least 1 month after immunization.
See
Table 3.2 for a
summary of the varicella vaccine schedule, indications, precautions, and booster
recommendations. CholeraOral Cholera Vaccines Oral cholera vaccines provide better immunity and fewer side effects than the previously available injectable vaccine.
To prevent cholera Cholera vaccine is not routinely recommended for travel to countries where cholera is reported active because the risk to the average international traveler of getting the disease is extremely low. The vaccine, however, is indicated for (1) people such as relief and healthcare workers operating in a high-risk environment—for example, working in a refugee camp or helping with disaster relief in an endemic or epidemic area, and (2) persons located in remote areas where cholera endemics or epidemics are occurring and there is limited access to medical care. An example might be someone doing archeological work in a remote endemic area. To prevent travelers' diarrhea The use of the oral cholera vaccine containing recombinant cholera toxin B-subunit (Dukoral) to provide crossover protection against travelers' diarrhea caused by enterotoxigenic E. coli (ETEC) is discussed below. Vaccination against Enterotoxigenic E. coli (ETEC)The most frequent cause of travelers’ diarrhea is a toxin-producing bacterium, enterotoxigenic E. coli (ETEC). This bacterium accounts for up to 60% of travelers’ diarrhea worldwide. Because of similarities between the heat-labile toxin of ETEC and the cholera toxin, it has been proposed that the recombinant toxin-whole cell vaccine (Dukoral®) may also afford some protection against travelers' diarrhea. To protect against ETEC the vaccine is administered in two doses, 1-6 weeks apart. If a booster dose is not given within 5 years, the two-dose schedule must be repeated. Travelers who would most benefit from the modest increase in protection provided by this vaccine include:
Note: A recent study in the journal Lancet notes that while a median of 21% of travelers' stool samples are positive for ETEC, only 6% to 10% are of the heat-labile-toxin-producing type. Since Dukoral provides about 65% cross protection against the heat-labile-toxin-producing strains, Dukoral can be expected to provide only 7% or less protection against travelers' diarrhea caused by ETEC. However, it is important to note that other studies have shown that a greater proportion of those with travelers’ diarrhea are infected with ETEC heat-labile toxins (approximately 60%); therefore the protection against travelers’ diarrhea Dukoral vaccine provides may be as high as 30%. The vaccine should be considered only as an adjunct to dietary precautions and treatment with antibiotics. Even if you are vaccinated, you should not have a false sense of security; you should still carry Imodium and an antibiotic for the self-treatment of diarrhea. See Table 3.2 for vaccine schedule, indications, precautions, and booster recommendations. Diphtheria-Tetanus-PertussisDiphtheria, caused by the bacterium Corynebacteria diphtheriae, manifests with a severe sore throat (pharyngitis) and sometimes heart damage (myocarditis) from the diphtheria toxin. Diphtheria is spread person-to-person through close contact and respiratory secretions. Pertussis, commonly called whooping cough, is caused by the bacterium Bordetella pertussis and is also spread by the respiratory route. Pertussis is the most frequent infectious cause of persistent cough lasting longer up to 12 weeks. It is also under-reported and under-diagnosed because most people believe, as they do about diphtheria, that the disease doesn’t occur, or is very rare, in adults.*Recent studies in the US and Canada show that whooping cause is on the rise in adolescents and young adults.* Tetanus is not spread person-to-person; it is caused by a toxin secreted by Clostridium tetani a bacterium that is found in soil and acquired by contamination of an open wound or sore. It may be present as a localized infection commonly termed “lockjaw”—so-called because of the paralysis and spasm of muscles, including those of respiration. The DTaP vaccine, which protects against diphtheria, tetanus, and pertussis, is a routine childhood immunization in the United States and Canada. It is a 5-dose series starting at 2 months of age and finishing at 4 to 6 years of age. It is frequently given in combination with the Haemophilus influenzae (Hib) vaccine. Following completion of the childhood DTaP series, the tetanus/diphtheria (Td) vaccine is used to maintain immunity against tetanus and diphtheria in adolescents and adults, with boosters recommended every 10 years. The Td vaccine, however, provides no on-going protection against pertussis, a disease that is making a resurgence among adolescents and young adults. Until recently, DTaP vaccines were not administered after the seventh birthday; now, however, an acellular dTap vaccine is available in Canada for children over six years of age and adults who have not completed their basic immunization series and in the United States, the Food and Drug Administration (FDA) has approved an acellular pertussis Tdap vaccine (ADACEL®) for a single booster immunization against pertussis, in combination with tetanus and diphtheria, for adolescents and adults. (ADACEL contains the same components as the DTaP vaccine for infants and children, but the diphtheria toxoid and one of the pertussis components are in reduced quantities.) Introduction of trivalent Tdap vaccines will soon make it possible to maintain immunity after childhood against all three of these diseases with a single vaccine. See below for more information on ADACEL in the section on tetanus. Haemophilus Influenzae Type b (Hib)Haemophilus influenzae Type b is a bacterial infection primarily of children, that is spread by the respiratory route and causes meningitis. Hib vaccine is a routine childhood immunization in the United States. This is a four-dose series (it may be a three-dose series depending on the brand of Hib vaccine used) starting at 2 months of age and finishing at 12 to 15 months of age. Many pediatricians give this vaccine in combination with the DTaP vaccine. Because infection with H. influenzae is rare after 5 years of age, older children and adults do not routinely need this vaccine. H. influenzae type b disease is common in many countries of the world. Every child should be vaccinated against this disease before international travel. Note: Haemophilus influenza type b disease and viral influenza (“the flu”) are different illnesses. The similarity of their names acknowledges their historical association. See Recommended Immunization Schedules for Persons Aged 0-18 Years for Hib vaccine schedule. recommendations. Hepatitis AHepatitis A is a viral infection of the liver that is acquired by ingestion of contaminated food and water. It is very frequent in developing countries where personal hygiene and sanitation are substandard. Poorly cooked shellfish are an important source of infection because they may be grown in water that is contaminated by raw sewage. Hepatitis A vaccine is recommended for all previously unvaccinated travelers older than 1 year of age going to lesser-developed countries with high or intermediate risk of hepatitis A. Hepatitis A is one of the most frequent vaccine-preventable diseases of travelers, and there are three vaccines available in the United States: Vaqta (Merck), Havrix (GlaxoSmithKline) and Twinrix (GlaxoSmithKline)—a combination of the hepatitis A and B vaccines. In Canada Avaxim (Sanofi-Pasteur) is available. The vaccines give rise to antibodies within 2 weeks after a single injection. A second dose, recommended 6 to 12 months later, dramatically boosts antibody levels and provides virtually 100% immunity—probably for life. If a person’s hepatitis A immune status is unknown, he or she may choose to be vaccinated or blood may be tested for existing immunity. People who have had the disease do not need vaccination; vaccinating people who are already immune, however, causes no harm. Hepatitis A vaccine generates antibodies in about 2 weeks, soon enough to protect healthy people against clinical hepatitis, even if the traveler is exposed to the virus immediately upon arrival at his destination. In other words, vaccination, even at the last minute, is effective and immune globulin (IG) is not always necessary. In the United States is recommended that travelers over age 40, those with chronic liver disease and other chronic conditions, and immunocompromised persons, should receive an initial dose of vaccine and simultaneously be given IGs (see below) to provide extra protection. Immune Globulin (IG)Immune globulin (also known as IG, immune serum globulin, ISG, or gamma globulin) is not a vaccine but rather a high concentration of antibodies against a variety of infections, particularly hepatitis A. Although IG contains pooled human blood products, it has never been shown to transmit infectious disease, such as HIV. It is effective for preventing hepatitis A in international travelers (for 3 to 5 months, depending on the amount given), but it has been largely supplanted by hepatitis A vaccine for this purpose. Since the introduction of hepatitis A vaccine in 1995, the use of IG has markedly decreased. Since hepatitis A vaccine is not approved for children younger than 1 year of age, they are usually given immune globulin or nothing at all since these children rarely develop symptoms if infected with HAV but do have the potential to pass the infection on to others. Older persons and immunocompromised travelers are less likely to respond to hepatitis A vaccine, as are those with chronic liver disease and other chronic illnesses; according to CDC recommendations they should receive IG, in addition to the vaccine. However, currently there is a shortage of IG, making it very difficult to obtain. *If immune globulin is not available, infants can be given 3 doses of hepatitis A vaccine (Havrix Pediatric 720 units) which will result in 100% seroconversion. The off-label vaccination schedule for infants age >2 months is 3 doses at 2, 4, and 6 months. Current Recommendations for Use of IG Travelers >40 years of age, immunocompromised persons, and those with chronic liver disease or other chronic medical conditions who have less than 2 weeks before departure may receive a single intramuscular dose of immune globulin (0.02 mL/kg) at a separate anatomic site in addition to the initial dose of vaccine. Note: IG can interfere with replication of live viruses in vaccines. Experience has shown that this occurs only with measles, mumps, and rubella vaccine (MMR) and with the varicella vaccine, not with the hepatitis A vaccine. Therefore, these vaccines should not be administered in the period from 2 weeks before IG is administered until several months after the IG. If IG must be given soon after MMR or varicella, these vaccines must be repeated at a later date. See Table 3.2 for immune globulin schedule, indications, precautions, and booster recommendations. Hepatitis BHepatitis B is a viral infection that attacks the liver. It is transmitted by contact with blood and body fluids through sexual activity, contaminated injection equipment (primarily needles and syringes), handling of blood products, and from an infected mother to child at birth. Hepatitis B vaccine is a routine immunization for all infants, children, and adolescents in the United States who are 18 years of age and younger. The vaccines now used in the United States and Canada are produced by recombinant DNA technology. The duration of protection after three doses of vaccine is considered to be lifelong. Serum antibody levels are not routinely measured when the vaccine is administered for travel. However, if antibody levels are tested, and a traveler does not develop hepatitis B antibodies 1 month after the immunization series has been completed, he or she is considered to be a “non-responder.” If time is available, the administration of extra vaccine doses should be considered. It is important to understand that one-third of those who develop immunity (antibody levels >10 IU/mL) will lose their antibodies within 5 years and still be protected for life because of the body’s “immune memory.”
The highest risk groups include:
See Table 3.2 for vaccine schedule, indications, precautions, and booster recommendations. InfluenzaInfluenza is a contagious viral disease that occurs worldwide, and travel increases exposure. Because the influenza viruses change continually and vary geographically, vaccines need to be reconstituted each year to reflect this change. In the Northern and Southern hemispheres influenza outbreaks occur during the cool winter months—whereas in the tropics, infection occurs year-round. The influenza vaccine is now a routine immunization in the United States for children ages 6 to 23 months, adults 50 years of age and older, those with underlying medical problems—such as chronic obstructive lung disease, heart disease, diabetes, and malignancy, and women who expect to be pregnant during the flu season—but travelers of any age going to countries where influenza activity is reported should be immunized. In North America and Europe, the optimum time to receive this vaccine is annually from mid-October through November. See Table 3.2 for influenza vaccine schedule, indications, precautions, and contraindications. Southern Hemisphere Vaccine Travelers to Australia, New Zealand, South America, and South Africa between April and October, should consider vaccination at their destination site with the influenza vaccine formulated for the Southern Hemisphere. This vaccine is not licensed in the United States and has a slightly different formulation. Note: Antiviral medication complements vaccination. As of 2006, the CDC is no longer recommends the anti-flu drugs amantadine or rimantadine for the prevention or treatment of influenza. This recommendation is based on laboratory testing by the CDC which showed that the predominant strain of influenza was resistant to these drugs. The CDC is currently recommending either Tamiflu or relenza be prescribed if an antiviral medication is needed for the treatment of prevention of influenza.
Table 3.1 Antiviral Agents for Influenza
Japanese Encephalitis (JE)Japanese encephalitis, a severe viral infection of the brain, is transmitted by an evening and night-biting mosquito in rural areas of South and Southeast Asia. Seasonal transmission occurs in northern areas (summer); whereas in the south, year-round transmission occurs. Three doses of JE vaccine, administered over a 30-day period (at 0, 7, and 30 days), are recommended for travelers who will be at risk (see Chapter 9). A two-dose schedule (at 0 and 14 days) may be used when the 30-day schedule is impractical. Two doses will give about 80% protection. If neither schedule is possible, two doses of vaccine, administered 1 week apart, will offer some protection. It is advisable to receive the last injection of vaccine a minimum of 10 days before departure to (1) allow time for immunity to develop and (2) have access to medical care if any side effects occur. Severe side effects from this vaccine include urticaria (hives), angioedema (edema of the face or other body parts), and hypotension (low blood pressure). These symptoms are quite rare (less than six cases per 100,000 doses of vaccine) and usually occur within a few days following immunization, but may be delayed 7 to 10 days. Because of the risk of delayed side effects, if possible, travelers should avoid international travel within 10 days of their last dose of JE vaccine. Travelers at risk should not forgo the immunization because they have fewer than 10 days before departure. The adverse effects of immunization need to be weighed against the risk of infection, which can be fatal in 10% to 25% or lead to permanent brain damage in as many as one third of symptomatic people. See Table 3.2 for Japanese encephalitis vaccine schedule, indications, precautions, and contraindications.
Lyme DiseaseNo vaccine is currently available. A Lyme disease vaccine (LYMErix, GlaxoSmithBeecham) was licensed in the United States in 1998 but was withdrawn from the market in 2001. MeaslesMeasles (rubeola) is a viral infection, spread by the respiratory route, that has the potential to cause severe illness in young children, especially those who are malnourished; it is one of the leading causes of death among children worldwide. The World Health Organization is hopeful that measles (rubeola) will be eradicated worldwide by the year 2010. All cases now occurring in the United States originate abroad, brought in by travelers, many of them foreign students attending U.S. secondary schools and colleges. Measles continues to be a major health problem in many developing countries, especially in sub-Saharan Africa and on the Indian subcontinent. Travelers to less developed countries should be immune to measles, either by having had the disease, or by immunization. Occasionally, there are reports of measles in developed countries—such as recent outbreaks in Holland , Ireland. With the decreased uptake of measles vaccine (MMR) in the UK due to fear of vaccine side effects (unsubstantiated) measles is considered to be endemic in the UK once again.. Many adult travelers, however, may not be immune to measles. Measles vaccination in the United States began in the late 1950s. People born before 1957 (before 1970 in Canada) are assumed to have had the disease during childhood and therefore have lifelong immunity. In fact, even when measles was prevalent and “everyone got it,” some individuals escaped the disease and remain susceptible. This number is higher than is generally appreciated. The same is true for mumps, rubella, and varicella (chickenpox.). It should be noted that all of these diseases are far more severe when they occur in adults—making immunity especially important for older people.In the mid-1960s, when effective live virus vaccines were introduced, experts believed that one dose would provide lifelong immunity. But experience has shown that immunity from measles vaccine is all or none—a “take” or a “no take”—and one dose immunizes only about 90% of those vaccinated; the second dose immunizes most of the rest. Therefore, travelers born after 1957 in the U.S. or between 1970 and 1996 in Canada should have a second dose of measles vaccine if they have not already received two doses. Measles vaccine (given as MMR—measles, mumps, rubella combination) is a two-dose series given on or after the first birthday and again at 4 to 6 years of age, but it is acceptable to give the two doses any time with as little as 1 month between them. The MMR vaccine should not be given during pregnancy, and female patients should not become pregnant for at least 3 months after immunization. Note: It is not contraindicated to give MMR to a breastfeeding mother. For babies ages 6 to 11 months traveling to countries where measles is endemic (e.g., India), a single dose of monovalent measles (MMR is acceptable) is recommended. If the vaccine is given at ages 6 to 11 months, a routine MMR is still recommended at age 1 year or as soon after as practicable. Maternal-derived antibodies protect infants younger than 6 months of age. See Table 3.2 for measles vaccine schedule, indications, precautions, and booster recommendations. MeningococcalMeningococcal disease, which usually presents clinically as meningitis, is caused by the bacterium Neisseria meningitidis. There are five meningococcal serogroups. A, B, C, Y, and W135 that can cause disease, and these vary geographically in their worldwide distribution. There is currently no vaccine that protects against serogroup B. The quadrivalent meningococcal polysaccharide vaccine (Menomune®, Sanofi Pasteur) protects for 3 years against four serogroups: A, C, Y, and W135. In January 2005 the Food and Drug Administration licensed the quadrivalent conjugate vaccine Menactra® (Sanofi Pasteur). This vaccine is more immunogenic in infants, is longer lasting, and eliminates the nasal carriage of meningococcal bacteria—a critical factor in preventing the spread of disease. Menactra® is approved for ages 2 to 55, but the vaccine can be administered “off-label” to both younger (>3 months) and older travelers who are headed for meningitis endemic or epidemic areas. Current recommendation Use the conjugate vaccine Menactra® for all immunizations against meningitis. Only use the polysacharide vaccine, Menomune®, if Menactra®, is not available. A bivalent meningococcal vaccine against serogroups A and C is available in Europe and the United Kingdom and two conjugate group C vaccines (Menjugate, Neisvac) are available in Canada. Because of their limited coverage (one or two serogroups only), these vaccines are not ideal for travelers. A quadrivalent vaccine (Menomune or Menactra), covering all four serogroups is recommended for travelers going to countries within the meningitis belt of sub-Saharan Africa (serogroups A, C, W-135 prevalent), or to outbreak areas, and is a requirement for travel to Saudi Arabia. Meningococcal serogroup W-135 has recently emerged as an important cause of meningitis in Saudi Arabia. All travelers to Hajj or Umrah will be asked by the Saudi Arabian embassy for proof of meningitis ACYW-135 vaccination on applying for their visa. The embassy requires that the vaccine should be administered at least 10 days before travel. Proof of vaccination is currently valid for a period of three years, but this is likely to change with the introduction of the longer-lasting conjugate vaccine. Two doses of meningococcal ACWY vaccine are required for children ages six months to two years, with an interval of three months between the two doses. The vaccinating center must provide a vaccination booklet or letter completed with the traveler’s name, vaccine, date of administration, and signature. Note: Meningococcal vaccine is usually not recommended for children under two years of age but under special circumstances (e.g., travel to Saudi Arabia) may be administered to infants as young as 3 months. The conjugate vaccine should be used, if available. The CDC no longer recommends the meningococcal vaccine for routine travel to Nepal, India, Mongolia, Kenya, Burundi, or Tanzania. In June 2005, however, an outbreak of meningococcal meningitis was reported in Delhi, India.See Table 3.2 for meningococcal vaccine schedule, indications, precautions, and booster recommendations. Pertussis (Whooping Cough)Pertussis, caused by Bordetella pertussis is a bacterial infection transmitted by the respiratory route that produces whooping cough. Pertussis infects an estimated 60 million people worldwide annually, causing 600,000 deaths, mostly children in developing countries. It can be a serious disease, especially in infants, and it is highly contagious. Pertussis is characterized by choking and coughing—often prolonged for many weeks. Pertussis vaccine is administered to children as the DTaP vaccine (diphtheria, tetanus, and acellular pertussis). However, the vaccine is not 100% protective, and vaccinated children may still become infected (although the disease tends to be milder), making it important to limit exposure to the disease. Immunity from vaccination lasts about 10 years, making older teenagers and adults susceptible, but for a generally milder form of the disease. CDC now recommends that all adults, whether or not they are traveling, should be given at least one dose TdaP (Adacel) in place of their 10-year booster of Td. See Table 3.2 for DTaP vaccine schedule, indications, precautions, and booster recommendations. See Diphtheria-Tetanus-Pertussis for an update on pertussis vaccines for adolescents and adults. Until now, a pertussis vaccine for adolescents and adults was not available. Polio (Poliomyelitis)Poliomyelitis is a highly contagious infection caused by poliovirus, which is transmitted person-to-person through exposure to fecal material or respiratory secretions containing the virus. Polio has been eradicated from much of the world, including the Western Hemisphere, Europe, and Southeast Asia, but there has been a recent resurgence of polio in Africa, chiefly in Nigeria. Polio has been spreading from northern Nigeria since 2003, when vaccination campaigns there were halted because of rumors that the vaccine could make people sick, or cause AIDS. Most cases from the outbreak have been in the Muslim Sahel, the band of arid land south of the Sahara stretching from Mali to Ethiopia. Polio has now appeared in Saudi Arabia and Yemen. The remaining pockets of polio in the world are in Pakistan, northern India, Afghanistan, Egypt, and Indonesia. Persons who have received a complete series of polio vaccine, either IPV (inactivated polio vaccine) or OPV (oral polio vaccine) should receive an additional single dose of vaccine (one lifetime dose only) if they are 18 years of age or older and are traveling to a polio-endemic area. These areas include Africa, the Middle East, and the Indian subcontinent. This additional (booster) dose of polio vaccine is necessary only once in adulthood. Only inactivated polio vaccine (IPV) should be used for this dose. OPV can, very rarely, cause paralytic polio in the recipient, or nonimmune persons in contact with the recipient. Therefore, OPV is no longer manufactured or administered in the United States—only injectable polio vaccine (IPV) is used. OPV, however, is still widely used in the rest of the world. The only circumstances in which OPV should be used are the following:
See Table 3.2 for polio vaccine schedule, indications, precautions, and booster recommendations. RabiesRabies is a uniformly fatal viral infection of the brain transmitted by the bite of an animal, usually a dog or monkey in the developing world, and by bats, skunks, foxes, and raccoons in North America. Rabies vaccine is recommended for long-stay travelers to endemic areas, particularly children, who are often attracted to animals and who are less likely to report a bite or scratch. The primary series of rabies vaccine is a total of three injections given at intervals of 0, 7, and 21 or 28 days. For travelers, two boosters are required only when an individual is potentially exposed to the virus. Veterinarians and spelunkers should receive a booster every 2 to 3 years. The main advantage of giving pre-exposure rabies vaccine is to eliminate the need for rabies immune globulin (to inject into the bite-site) at the time of the exposure. Rabies immune globulin is often very scarce in the developing world, whereas rabies vaccine is usually readily available. Therefore, an animal bite could be a trip-ending experience if one is forced to fly to another city or country, or even home, to obtain rabies immune globulin. Also, pre-exposure vaccination reduces the number of doses of post-exposure vaccine, and possibly lengthens the safe interval between animal exposure and the onset of treatment. It does not preclude the essential step of proper wound cleansing with soap and water. Rabies intradermal vaccine is not recommended when travelers are taking chloroquine or mefloquine for malaria prevention. The intramuscular formulation should be used. The intradermal rabies vaccine series, if used, should be started 30 days before the administration of either chloroquine or mefloquine. Three types of rabies vaccine, all equally effective, are available in the United States. See Table 3.2 for rabies vaccine schedule, indications, precautions, and booster recommendations. See Table 3.2 for rabies vaccine schedule, indications, precautions, and contraindications. Rubella (German measles)Rubella, or German measles, caused by the rubella virus, is usually a mild infection in children but a very serious infection if it occurs during pregnancy because of severe damage to the developing fetus. Most Americans and Canadians are immune to rubella, either by having had the disease, or by vaccination with the measles-mumps-rubella (MMR—Merck) vaccine. For the past 2 decades, nearly all children have been receiving two doses of MMR vaccine. The only travelers who need the rubella component of the vaccine are women who may become pregnant and whose rubella immunity status is unknown. These women should consider receiving one dose of MMR. One dose of the rubella component immunizes virtually 100% of recipients for life. Rubella Vaccine and Arthritis About 10% to 25% of postpubertal women report joint pain after receiving rubella vaccine and about 10% report arthritis-like signs and symptoms. When joint symptoms occur, they generally begin 1 to 3 weeks after vaccination, persist for 1 day to 3 weeks, and rarely recur. Tetanus/Diphtheria (Td)Tetanus is an infectious complication of wounds, caused by the toxin of Clostridium tetani bacteria. This organism is found worldwide in the soil and in the feces of various animals and some humans. When wounds become contaminated with soil containing the spores of C. tetani; the spores germinate and the resulting bacteria produce a toxin that is absorbed into the central nervous system, resulting in severe muscle contractions and spasms, respiratory paralysis, and sometimes death. Tetanus is a global health problem, occurring particularly among infants and young children in developing countries. In the United States, most infections are seen in the elderly who have never received a primary series of injections. The tetanus/diphtheria vaccine (Td vaccine) is a routine immunization in the United States. Following completion of the DTaP (Diphtheria, Tetanus, and acellular Pertussis) series (by the seventh birthday), Td is given at 11 to 12 years of age if at least 5 years have elapsed since the last dose of DTaP. Subsequent Td boosters are recommended every 10 years. The schedule for tetanus immunization is identical to that for diphtheria, and the two vaccines are generally combined in one product. Table 3.2 Immunizations for International Travel
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