MIAMI BEACH — Accelerated immunizations for pediatric travelers can optimize disease prevention before international travel, Elizabeth D. Barnett, M.D., said at the annual meeting of the American Society of Tropical Medicine and Hygiene.
Hepatitis A, typhoid fever, yellow fever, Japanese encephalitis, meningococcal infection, and rabies infection are some of the leading concerns for pediatric travelers, according to Dr. Barnett, director of the International Clinic, Maxwell Finland Laboratory for Infectious Diseases, Boston Medical Center.
The good news is that most traveling children have already received vaccines for hepatitis B and pneumococcal disease.
Age is important in terms of immune system maturation. For example, efficacy of polysaccharide vaccines will be limited until age 2 years because of impaired T-cell function. “The solution is development of conjugate vaccines,” Dr. Barnett said. In addition, maternal antibodies can impair response to some vaccines in very young infants, such as the measles, mumps, and rubella (MMR) and hepatitis A vaccines. “Balance the lower age limit of the vaccine with risk of disease and vaccine efficacy.”
If travel to a measles-endemic area is planned, consider giving MMR beginning at 6 months of age, Dr. Barnett suggested. If the patient is traveling to a region where a polio outbreak is possible, he or she should receive a full course of polio vaccination beforehand.
Dr. Barnett made some specific recommendations:
▸ Hepatitis A. Hepatitis A vaccine should be given 2-4 weeks prior to departure for children traveling to all international destinations except Australia, Canada, Japan, New Zealand, Western Europe, and Scandinavia. Children at least 1 year old can receive the vaccine; the only option for younger travelers is immune globulin. “If the time to departure is short, consider giving immune globulin and vaccine at the same time as MMR or varicella vaccines at different sites,” Dr. Barnett said. However, there is a theoretical risk that immune globulin may impair vaccine activity for weeks or months, so the ideal situation is to give the vaccine first, followed at least 2 weeks later by the immune globulin.
“The benefit really outweighs the risks with hepatitis A vaccine,” Dr. Barnett said.
▸ Typhoid. Vaccination is indicated for travel to areas where exposure to contaminated food or water is possible. Risk is not dictated by length of trip but by behaviors and exposure. The vaccine's efficacy is limited compared to hepatitis A, Dr. Barnett said. “We generally tell patients the efficacy is 65%-85%.”
For infants under 2 years, there are only food and water precautions. From ages 2-5 years, the same precautions plus a polysaccharide vaccine are recommended. For children 6 years and older, the parenteral polysaccharide vaccine, Ty21a oral vaccine, and food and water precautions are recommended. Adverse events with the parenteral vaccine include local reactions (7%), headache (1.5%-3%), and fever (0%-1%).
Dr. Barnett said, “In most settings, the benefit for typhoid vaccine is there, limited by incomplete vaccine efficacy.”
▸ Yellow fever. Vaccination for yellow fever is only a consideration for travel to Africa and South America. There are an estimated 0.4-4.3 cases of yellow fever per million U.S. travelers to endemic areas. The vaccine is very efficacious, with a single vaccination usually providing lifetime coverage.
“Encephalitis is a rare adverse event following yellow fever vaccine, occurring primarily in infants,” Dr. Barnett said. “The vaccine, therefore, is absolutely contraindicated in infants under 6 months.”
“The bottom line is, those who are at risk for yellow fever going to high transmission areas, and who cannot guarantee mosquito protection, should receive yellow fever vaccine unless there are specific contraindications,” Dr. Barnett said.
▸ Japanese encephalitis. There is an effective vaccine, and it is indicated for some travel to higher-risk areas, Dr. Barnett said. “We have to again balance risks and benefits.” The risk is greater in rural farming areas, during transmission season, and during outbreaks.
▸ Meningococcal infection. Sub-Saharan Africa has frequent epidemics and outbreaks. “The overall risk of disease for travelers to sub-Saharan Africa is very low, but the vaccine is safe, effective in children over 2, and offers some protection at home,” Dr. Barnett said. Although conjugate vaccines are available in Canada and Europe, only polysaccharide vaccines are available in the United States. With polysaccharide vaccines, there is superior efficacy in children aged 2 years and older.
▸ Rabies. Although the benefits of prophylaxis are greatest for travel to high-risk areas and areas far from medical care, and for travel of long duration, “I believe we should be discussing prevention with all families traveling to a destination that is not rabies-free,” Dr. Barnett said.