Vaccines for Travel and International Adoption
Vaccines for Travel and International Adoption
Vaccines have been one of the most important health advances of the 20th century. As more children emigrate from and travel to underdeveloped countries where they can be exposed to unusual endemic pathogens beyond their previous immunologic experience, it is critical to protect them against these potentially life-threatening infections.
The basic rule for all international travelers is they should have received the U.S. recommended immunizations, which include tetanus, diphtheria, polio, measles, mumps, and rubella. Most children and adolescents have received vaccines for pertussis, hepatitis B (HBV), H. influenzae b (Hib), varicella, and S. pneumoniae (PCV7). Infants and toddlers who were born since 2006 may have received rotavirus, hepatitis A (HAV), and influenza vaccines. Recently vaccinated adolescents may have received pertussis, meningococcal, and human papillomavirus vaccines. Pediatricians also may have given HAV and influenza vaccines to patients older than the current recommended ages. Because of ongoing updates and changes to the recommended vaccine schedule, it is important to check the patient's vaccine record to ensure they are not missing age-appropriate immunizations because of previous shortages or the introduction of new vaccines.
Children and adolescents are typically up-to-date on their vaccines because of school requirements and the frequency of visits to the pediatrician. However, the same is often not true of their parents. Parents should be counseled to make sure their tetanus and diphtheria immunization status is current. If indicated, a tetanus/diphtheria booster containing acellular pertussis should be given once if the adult is <65 years old. One lifetime booster for polio is recommended for adults who travel internationally. Adults born in or after 1957 may require a measles booster. The majority of adults have not received HBV, HAV, or even the annual influenza vaccine.
Yellow fever is a rare, but potentially fatal flaviviral infection transmitted by mosquitoes. Yellow fever vaccine (YFV) (see Table 1 ) is only indicated for patients traveling to areas with endemic YF or where YF has been reported, which includes both rural and urban areas in sub-Saharan Africa and Central/South America year-round. The most up-to-date YFV travel requirements are available on the CDC website at http://wwwn.cdc.gov/travel/yellowBookCh5- MalariaYellowFeverTable.aspx. Rare (~0.5/100,000 doses) complications, such as viscerotropic disease (resulting in multiorgan system failure) and neurotropic disease (causing a vaccine associated encephalitis), have been reported. The risk is 3-4 times higher in patients with thymic dysfunction or other immunodeficiency, and in travelers >60 years of age. YFV should not be given to children younger than age 4 months, and should only be given to children younger than 9 months in consultation with a travel medicine expert and/or the CDC Vector-Borne Diseases Branch (970-221-6400), because there is a higher rate of neurotropic complications in this age range. Children too young for immunization and immunosuppressed patients should be given a medical waiver letter.
YFV must be given by a certified provider. A relatively comprehensive listing of sites providing YFV and the International Certificate of Vaccination or Prophylaxis (ICVP), which is the only accepted documentation of YF vaccination, is available from the CDC website at http://www2.ncid.cdc.gov/travel/yellowfever/. Travelers who arrive to or from an endemic country without a complete or valid ICVP can be denied entry or be quarantined, unless the traveler has a valid medical waiver letter or agrees to on-site vaccination. The ICVP becomes valid 10 days after vaccination and remains valid for 10 years. Although countries in endemic areas require a booster after 10 years for travel, data suggests immunity may last >25-35 years. The immune response to YFV is not inhibited by administration of other live attenuated vaccines, such as oral typhoid or measles, concurrently or at various intervals of a few days to 1 month.
Salmonella typhi is endemic in most countries, and travelers to Asia, Africa, and Latin America are at highest risk. Up to 33 million cases of typhoid occur annually, with the highest incidence in children ages 5-19. Mortality can be as high as 30% in the untreated. Typhoid vaccine should always be considered for travel to endemic areas, and recommended for stays >2 weeks. There are 2 vaccines licensed in the United States: the polysaccharide injection Typhim Vi and the live attenuated oral Vivotif (see Table 1 for further details). Use of antimicrobials, including the antimalarial agents proguanil and atovaquone, should be avoided for at least 24 hours before starting, and 7-10 days after completing Vivotif. These agents interfere with the replication of the Ty21a strain in the gut, and diminish the body's immune response. Mefloquine and chloroquine do not affect the vaccine's immunogenicity.
JE vaccine (JE-VAX) (see Table 1 ) is recommended for stays >4 weeks in endemic areas, because JE is the leading cause of viral encephalitis in Asia and children <15 years old are primarily affected. JE virus (JEV) is also a flavivirus transmitted by mosquitoes. There is a 0.5% incidence of serious immediate and delayed vaccine associated hypersensitivity reactions, so it is not recommended for short term travelers unless there is high risk of infection (ie, prolonged outdoor activity in rural areas during transmission season). Although JE-VAX is usually given in 3 doses over a 1-month period, an abbreviated 2-week schedule given at days 0, 7, and 14 can be used if travel is imminent. Neutralizing antibody titers with this shorter schedule are significantly lower, although seroconversion rates among recipients are similar. The longevity of JEV neutralizing antibody is unknown, but seems to be at least 2 years. The most current recommendations for use of JE-VAX are available at http://www.cdc.gov/ncidod/dvbid/jencephalitis /index.htm. JE-VAX is the only JE vaccine currently available or licensed in the United States; however, it has been discontinued by its manufacturer, with current inventory estimated to only last through mid-2008. Later in 2008, a next generation cell-culture derived JE vaccine developed by Intercell should be approved and available. A live attenuated JE vaccine has been used in Asia since 1998. A promising single dose inactivated vaccine (ChimeriVax-JE, Acambis) met and exceeded immunogenic efficacy in phase 3 efficacy trials in 2007, and has been licensed for Asia. Phase 3 pediatric trials are being conducted in India.
A 3-dose rabies pre-exposure series can be considered for travel to areas where contact with wild animals is likely, or when destination activities are likely to increase exposure to rabies (ie, spelunking). An initial measles vaccine (MMR or preferably monovalent measles) is recommended for infants 6-11 months of age, if travel to an endemic area cannot be avoided, followed by the standard 2-dose schedule. If there is increased risk of exposure, vaccination with HAV, influenza, and/or meningococcal vaccine should be considered if age or seasonally appropriate.
Vaccines have been one of the most important health advances of the 20th century. As more children emigrate from and travel to underdeveloped countries where they can be exposed to unusual endemic pathogens beyond their previous immunologic experience, it is critical to protect them against these potentially life-threatening infections.
The basic rule for all international travelers is they should have received the U.S. recommended immunizations, which include tetanus, diphtheria, polio, measles, mumps, and rubella. Most children and adolescents have received vaccines for pertussis, hepatitis B (HBV), H. influenzae b (Hib), varicella, and S. pneumoniae (PCV7). Infants and toddlers who were born since 2006 may have received rotavirus, hepatitis A (HAV), and influenza vaccines. Recently vaccinated adolescents may have received pertussis, meningococcal, and human papillomavirus vaccines. Pediatricians also may have given HAV and influenza vaccines to patients older than the current recommended ages. Because of ongoing updates and changes to the recommended vaccine schedule, it is important to check the patient's vaccine record to ensure they are not missing age-appropriate immunizations because of previous shortages or the introduction of new vaccines.
Children and adolescents are typically up-to-date on their vaccines because of school requirements and the frequency of visits to the pediatrician. However, the same is often not true of their parents. Parents should be counseled to make sure their tetanus and diphtheria immunization status is current. If indicated, a tetanus/diphtheria booster containing acellular pertussis should be given once if the adult is <65 years old. One lifetime booster for polio is recommended for adults who travel internationally. Adults born in or after 1957 may require a measles booster. The majority of adults have not received HBV, HAV, or even the annual influenza vaccine.
Yellow fever is a rare, but potentially fatal flaviviral infection transmitted by mosquitoes. Yellow fever vaccine (YFV) (see Table 1 ) is only indicated for patients traveling to areas with endemic YF or where YF has been reported, which includes both rural and urban areas in sub-Saharan Africa and Central/South America year-round. The most up-to-date YFV travel requirements are available on the CDC website at http://wwwn.cdc.gov/travel/yellowBookCh5- MalariaYellowFeverTable.aspx. Rare (~0.5/100,000 doses) complications, such as viscerotropic disease (resulting in multiorgan system failure) and neurotropic disease (causing a vaccine associated encephalitis), have been reported. The risk is 3-4 times higher in patients with thymic dysfunction or other immunodeficiency, and in travelers >60 years of age. YFV should not be given to children younger than age 4 months, and should only be given to children younger than 9 months in consultation with a travel medicine expert and/or the CDC Vector-Borne Diseases Branch (970-221-6400), because there is a higher rate of neurotropic complications in this age range. Children too young for immunization and immunosuppressed patients should be given a medical waiver letter.
YFV must be given by a certified provider. A relatively comprehensive listing of sites providing YFV and the International Certificate of Vaccination or Prophylaxis (ICVP), which is the only accepted documentation of YF vaccination, is available from the CDC website at http://www2.ncid.cdc.gov/travel/yellowfever/. Travelers who arrive to or from an endemic country without a complete or valid ICVP can be denied entry or be quarantined, unless the traveler has a valid medical waiver letter or agrees to on-site vaccination. The ICVP becomes valid 10 days after vaccination and remains valid for 10 years. Although countries in endemic areas require a booster after 10 years for travel, data suggests immunity may last >25-35 years. The immune response to YFV is not inhibited by administration of other live attenuated vaccines, such as oral typhoid or measles, concurrently or at various intervals of a few days to 1 month.
Salmonella typhi is endemic in most countries, and travelers to Asia, Africa, and Latin America are at highest risk. Up to 33 million cases of typhoid occur annually, with the highest incidence in children ages 5-19. Mortality can be as high as 30% in the untreated. Typhoid vaccine should always be considered for travel to endemic areas, and recommended for stays >2 weeks. There are 2 vaccines licensed in the United States: the polysaccharide injection Typhim Vi and the live attenuated oral Vivotif (see Table 1 for further details). Use of antimicrobials, including the antimalarial agents proguanil and atovaquone, should be avoided for at least 24 hours before starting, and 7-10 days after completing Vivotif. These agents interfere with the replication of the Ty21a strain in the gut, and diminish the body's immune response. Mefloquine and chloroquine do not affect the vaccine's immunogenicity.
JE vaccine (JE-VAX) (see Table 1 ) is recommended for stays >4 weeks in endemic areas, because JE is the leading cause of viral encephalitis in Asia and children <15 years old are primarily affected. JE virus (JEV) is also a flavivirus transmitted by mosquitoes. There is a 0.5% incidence of serious immediate and delayed vaccine associated hypersensitivity reactions, so it is not recommended for short term travelers unless there is high risk of infection (ie, prolonged outdoor activity in rural areas during transmission season). Although JE-VAX is usually given in 3 doses over a 1-month period, an abbreviated 2-week schedule given at days 0, 7, and 14 can be used if travel is imminent. Neutralizing antibody titers with this shorter schedule are significantly lower, although seroconversion rates among recipients are similar. The longevity of JEV neutralizing antibody is unknown, but seems to be at least 2 years. The most current recommendations for use of JE-VAX are available at http://www.cdc.gov/ncidod/dvbid/jencephalitis /index.htm. JE-VAX is the only JE vaccine currently available or licensed in the United States; however, it has been discontinued by its manufacturer, with current inventory estimated to only last through mid-2008. Later in 2008, a next generation cell-culture derived JE vaccine developed by Intercell should be approved and available. A live attenuated JE vaccine has been used in Asia since 1998. A promising single dose inactivated vaccine (ChimeriVax-JE, Acambis) met and exceeded immunogenic efficacy in phase 3 efficacy trials in 2007, and has been licensed for Asia. Phase 3 pediatric trials are being conducted in India.
A 3-dose rabies pre-exposure series can be considered for travel to areas where contact with wild animals is likely, or when destination activities are likely to increase exposure to rabies (ie, spelunking). An initial measles vaccine (MMR or preferably monovalent measles) is recommended for infants 6-11 months of age, if travel to an endemic area cannot be avoided, followed by the standard 2-dose schedule. If there is increased risk of exposure, vaccination with HAV, influenza, and/or meningococcal vaccine should be considered if age or seasonally appropriate.
