While most US infant and preschool-aged international travelers are eligible for measles-mumps-rubella (MMR) vaccination prior to departure, almost 60 percent of eligible young travelers were not vaccinated during pretravel consultation, researchers at Massachusetts General Hospital (MGH) have found.

In a study published in JAMA Pediatrics, the team reported that most eligible pediatric international travelers were not vaccinated due to clinician decision or guardian refusal, despite recommendations from the Advisory Committee on Immunization Practices (ACIP).

“At a time when the global resurgence of measles is evident in the US, our results show that clinicians too frequently miss opportunities to vaccinate eligible pediatric travelers with MMR,” Emily Hyle, MD, investigator in the Division of Infectious Diseases at MGH, and lead author of the study, says in a statement. “Children represent less than 10 percent of US international travelers but account for nearly half of known measles importations that trigger additional measles infections and outbreaks in the US.” Even young travelers to places not considered high risk for disease should be vaccinated, she adds, noting that Europe accounted for 30% of imported measles cases to the US from 2001 to 2016.

ACIP recommends that children in the US receive two lifetime MMR vaccine doses as part of routine vaccination. The first is given between 12 and 15 months and the second between 4 and 6 years of age. However, due to the increased risk of measles exposure for international pediatric travelers, ACIP recommends that infants (6 to 12 months) receive one MMR vaccination prior to departure (which does not count toward the two lifetime doses), and that preschool-aged travelers (1 to 6 years) should receive both lifetime vaccine doses before departure.

To assess how well ACIP recommendations were achieved, the research team evaluated consultations of pediatric travelers at the Global TravEpiNet (GTEN) sites, a multisite consortium around the country supported by the Centers for Disease Control and Prevention (CDC). Among more than 14,000 pediatric international travelers who sought pretravel health consultations from 2009-2018, 92% of infants and 60% of preschool-aged children were eligible for pretravel MMR vaccinations, yet 44% of those infants and 57% of preschool children were not vaccinated, often because clinicians failed to recognize the child’s eligibility.

“This underscores the knowledge gaps that exist about MMR vaccination, even among clinicians with expertise in travel medicine,” Regina LaRocque, MD, MPH, investigator in the MGH Division of Infectious Diseases, and senior author of the study, says in a statement.