NEW ORLEANS -- Experts here reminded travel medicine practitioners to modify treatment when caring for more vulnerable, high-risk groups such as immunocompromised individuals, children, and pregnant women planning travel abroad.
For pregnant travelers, the influenza and Tdap vaccines are recommended (though live-attenuated versions are to be avoided), and while inactivated travel vaccines are generally safe, practitioners should still consider the risks and benefits in each case, reported Lin Chen, MD, of Mount Auburn Hospital in Cambridge, Massachusetts at the American Society of Tropical Medicine and Hygiene (ASTMH) annual meeting.
For the immunocompromised, she said that clinicians should take into account the patient's underlying disease, any therapeutic agents they might be on (with consideration for interactions and toxicities), the possible risk of any vaccine in these patients (especially live versions), exposure risk, and the availability of medical care abroad.
High-risk travelers are not uncommon. Among 15,440 travelers assessed using the Boston Area Travel Medicine Network, about 18% fell into this category. Of those, 23% were immunocompromised, 74% had comorbidities, and 2.5% were pregnant. The median age was 47 for high-risk travelers compared with 32 for healthy travels.
Among these high-risk travelers, 94% visited regions where typhoid is of concern, 86% visited malaria-risk countries, and 23% visited yellow fever–endemic countries. Among those traveling to areas where yellow fever is endemic, 35% of pregnant women and 44% of immunocompromised received an indicated vaccine.
Pregnancy and Yellow Fever Vaccines
The CDC has guidelines for identifying appropriate travel immunizations during pregnancy. When it comes to the yellow-fever vaccine in pregnancy, a study in Trinidad found fetal infection for one of every 41 immunized women and a study in Brazil found an increased risk of spontaneous abortion among women who received the vaccine (RR 2.29, 95% CI 0.65-8.03).
In other reports from Brazil, there were no cases of fetal infection among 480 yellow fever–immunized women and no increased congenital defects in 304 infants of immunized mothers (except for more nevi). In a Nigerian study, no cases of transplacental infection occurred among 40 infants of immunized women, but there were lower seroconversion rates.
Pregnant Women With Malaria
When it comes to malaria in pregnancy, there is a risk of maternal and perinatal morbidity and mortality, and of lower immune response and inability to clear infections, Chen noted.
Pregnant women, especially those in their first pregnancy, are three times more likely to suffer from severe malaria, as the parasites often sequester and duplicate in the placenta, she emphasized.
Her presentation also highlighted many of the complications associated with malaria in pregnancy, including miscarriage, premature delivery, intrauterine growth restriction, low birth weight, anemia, and congenital infection.
Chloroquine and mefloquine are malaria chemoprophylaxis that can be used in pregnancy and for women breastfeeding. Not enough evidence exists to support the use of other malaria preventive agents like doxycycline, primaquine, and tafenoquine.
But other antimalarials are compatible with breastfeeding. However, as Chen pointed out, there are some caveats to the drugs listed below and they include:
- Atovaquone-proguanil: appropriate when infants weigh ≥5 kg (11 lb), as recommended by the CDC
- Doxycycline: could contribute to dental enamel staining and bone deposition, but it has been recommended for short-term use as outlined by the CDC and American Academy of Pediatrics (AAP), with dosing based on the mother's weight -- however, the World Health Organization (WHO) advised avoiding the drug
- Primaquine: compatible when glucose-6-phosphate dehydrogenase (G6PD) levels of both mother and child are normal
- Tafenoquine: also compatible when G6PD levels are normal for both
Zika and Pregnancy
Zika infection during pregnancy has contributed to severe birth defects, and pregnant women are advised not to travel to select parts of Africa, Asia, the Caribbean, Central America, North America, the Pacific Islands, and South America. Women planning to become pregnant should take precautions as well. Travelers are advised to take steps to avoid mosquito bites and prevent sexual transmission during and after the trip, Chen highlighted.
Researchers have advised preconception planning and waiting 3 months if men have been exposed to Zika. Previous reports have pointed to a culturable, potentially replication-competent Zika virus in semen species even after 40 days from the first symptoms. Another report showed detection of Zika in infected semen after 69 days.
The longest reported duration from the start of symptoms in index cases to potential sexual transmission was 32 to 41 days -- but many reports show intervals ≤30 days.
Moreover, Chen also highlighted that infectious Zika virus was only culturable in cases with high Zika RNA copies (>7.0 log10). At 60 days following the onset of sickness, all Zika virus RNA loads were below this level.
In closing, Chen noted, clinicians should advise pregnant travelers to take food and water precautions, carry their obstetric and medical records, and confirm that their patients have health insurance.
Travel Considerations for Children
There are challenges that should be taken into account when preparing children for travel.
Children should get the hepatitis A vaccine at 6 months of age, and they can also receive the meningococcal vaccine as early as 2 months old, reported Elizabeth Barnett, MD, of Boston Medical Center, at the ASTMH meeting.
Beginning at 2 months of age, clinicians can also give children the Japanese encephalitis vaccine.
Clinicians and parents need to consider if vaccines and medications are appropriate for the child's age. It is widely understood that children are more likely to be vulnerable when it comes to accidents, dog bites, diarrheal illness, and sun damage, and teens are more likely to engage in high-risk behaviors. There are a number of routine vaccines that children should get.
The influenza vaccine is also advised as it provides protection in the U.S. and abroad. Even after the age of 1 year, children still need a two-dose series of MMR (measles, mumps, and rubella) and hepatitis A, and children traveling outside of the U.S. should receive MMR beginning at the age of 6 months.
When it comes to travel vaccines, children 2 years and older can be treated with the typhoid vaccine (typhim Vi-polysaccharide) -- the oral vaccine capsule can be used for children 6 years and older.
For rabies prevention, clinicians should advise children to avoid animals and should encourage them to tell their parents about bites and other encounters with animals. Before traveling, families should come up with an action plan.
For rabies post-exposure prophylaxis in the U.S., the following immunizations are advised:
- For people who have not previously been immunized: a single 20 IU/kg dose of rabies immune globulin, and four 1.0 mL doses of the rabies vaccine
- For those who have been previously immunized: two 1.0 mL doses of the vaccine
In closing, Barnett suggested providing clear information concerning the risks of travel, while still taking into consideration what is being gained. Clinicians should "aid families in balancing risks and benefits of vaccines and medications to prevent travel-associated illness" and "provide information about how the family can reduce their risk of disease," she said.
Barnett and Chen did not report any disclosures.
American Society of Tropical Medicine and Hygiene Meeting
Source Reference: Chen L "Managing the high-risk traveler" ASTMH 2018.
American Society of Tropical Medicine and Hygiene Meeting
Source Reference: Barnett E "Travel with children" ASTMH 2018.