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Travel medicine: Recommendations for specific at-risk travelers
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Travel medicine is a dynamic science because of the constantly changing socioeconomic and political situations, as well as the epidemiology of infectious and other diseases across the globe.
The practice of travel medicine requires knowledge in medicine/pediatrics, vaccinations and epidemiology of infectious diseases and other conditions. International Society of Travel Medicine and American Society of Tropical Medicine and Hygiene have helped improve resources, including development of curriculum to enhance knowledge in travel medicine. Similarly, the CDC and WHO provide valuable information on travel medicine. In addition, GeoSentinel and TropNetEurop are two collaborative sentinel surveillance networks that collect data on the health problems affecting travelers. These networks also have helped improve pre-travel advice and post-travel management of travelers.
It is estimated that more than 1 billion travelers crossed international borders in 2012. However, only a small percentage of travelers seek pre-travel advice or are compliant with the recommendations provided by their health providers. This results in 15% to 70% of international travelers falling sick during or after travel. Fortunately, most of the illnesses are mild and only 1% to 5% of returned travelers are sick enough to seek medical attention. Many factors, such as countries visited, duration and type of travel, pre-travel vaccinations and adherence to travel precautions, etc, are taken into consideration while evaluating sick-returned travelers.
Travelers at increased risk
Visiting friends and relatives, adolescents and immunocompromised travelers comprise a special group of travelers. These travelers are at higher risks for contracting illnesses because they do not seek pre-travel advice, usually stay longer than tourists, and are not careful about consuming safe beverages and food or preventing mosquito bites. Besides not seeking pre-travel advice and not being compliant, adolescent travelers may participate in risky/adventurous activities/behaviors that increase their risk for contracting infections, such as sexually transmitted infections, including HIV, and also for accidents.
Deepak M. Kamat
Immunocompromised hosts include those with mild to moderate immunodeficiency conditions (nephrotic syndrome, diabetes and autoimmune disorders, etc), as well as those with severe immunodeficiency conditions (those on immunosuppressants after bone marrow and organ transplantations, congenital immunodeficiency syndromes, etc). With advances in management, survival among these patients has improved significantly, and therefore a large number of these individuals are traveling abroad for professional or personal reasons. Travel advice, as well as post-travel evaluation, of these individuals has to be undertaken by physicians experienced in managing immunocompromised travelers. Besides general pre-travel advice, which is provided to all travelers, these individuals also need individualized advice based on their immune status (underlying conditions, as well as their medications). It is advisable to consult with the traveler’s primary physician/s before advising the immunocompromised traveler and developing an individualized plan for travel.
Vaccines recommended for travel
Two main issues regarding travel vaccines for the immunocompromised hosts include lack/poor immune response to vaccines and inability to receive live vaccines. Immune responses to vaccines depend on the severity of underlying immunodeficiency, immunosuppressive medications being used and on the vaccines themselves (some vaccines are more immunogenic than others). In general, it is advised that immunocompromised individuals be vaccinated several months before travel and serologic assessment to be performed to check for protective antibody titer. In addition, many of these individuals may not sustain the antibody responses and, therefore, may need a booster series immediately before travel. The clinical significance of transient increases in HIV viral loads after vaccination is not known and should not preclude use of any vaccine.
Live vaccines, such as MMR (M-M-R II, Merck) and varicella (Varivax, Merck), may be administered to the traveler with mild immunodeficiency. However they are contraindicated for travelers with severe immunodeficiency, such as post-transplant patients (in general, at least 1 year after solid organ transplant and 2 years after hematopoietic stem cell transplant) for the risk of dissemination of vaccine viruses and causing significant illnesses.
In these situations, especially for seronegative immunocompromised travelers, intramuscular immunoglobulin should be considered. Depending on the dose injected, the recipients may be protected from 3 to 6 months. Of course, travelers who routinely receive intravenous immunoglobulin (IVIG) for their underlying immunodeficiency may not need MMR, varicella and hepatitis A vaccines because they may be protected by passively acquired antibodies. It is advisable to administer human rabies immunoglobulin after rabies exposure because the immunocompromised traveler may not have protective antibody titers, even after appropriate pre-travel immunization with rabies vaccine.
Yellow fever vaccine creates a unique situation for immunocompromised travelers who visit yellow fever endemic countries. This live virus vaccine can be given to travelers with mild immunodeficiency but not for those with severe immunodeficiency. In addition, it has been found that individuals with disorders of thymus, such as myasthenia gravis or thymoma, are at risk for yellow fever vaccine-associated viscerotropic diseases such as myeloencephalitis. Therefore, the options are to defer travel during the peak season for yellow fever transmission and be very vigilant in preventing mosquito bites. Most of the countries would accept a letter duly signed and stamped from a physician working in an approved yellow fever immunization center stating the reason for contraindication for yellow fever vaccine for those travelers who cannot receive this vaccine. However, some countries may deny entry without the vaccine, and therefore it is prudent to verify this before travel.
Bacillus Calmette-Guérin vaccine is not advisable for travelers with immunodeficiency. In addition, pre- and post-travel tuberculin test may not be helpful because it is likely to be negative in those with immunodeficiency.
Additional preventive strategies
Besides vaccines, other preventive measures such as consumption of appropriate beverages and food, malaria prophylaxis and sun protection are important for immunocompromised hosts.
Travelers’ diarrhea may cause dehydration and may interfere with absorption of oral immunosuppressants, and antibiotics used for self-treatment may interact with immunosuppressants, along with some medications used for prophylaxis and treatment of malaria. Because transplant patients are at risk for skin cancer, the use of sunscreens is of paramount importance.
Immunocompromised hosts also are prone to invasive fungal infections, and therefore activities such as excavating should be avoided.
For more information:
Deepak M. Kamat, MD, PhD, FAAP, is professor of Pediatrics, vice chair of Education, and the Carman and Ann Adams Department of Pediatrics at Wayne State University and the Designated Institutional Official at Children’s Hospital of Michigan, Detroit. He can be reached at Children’s Hospital of Michigan, 3901 Beaubien Blvd., Detroit, MI 48201; email: dkamat@med.wayne.edu.
Disclosure: Kamat reports no relevant financial disclosures.