MMR Vaccination

Emily P. Hyle, MD, on MMR Vaccination Rates Among US Pediatric Travelers

New findings published in JAMA Pediatrics shed light on current measles, mumps, and rubella (MMR) vaccination rates among US pediatric travelers, indicating that strategies may be needed to improve these rates.

Researchers arrived at this conclusion after performing a cross-sectional study of MMR vaccination rates among 14,602 pediatric travelers.

Among the study population, 91.7% of infants, 59.6% of preschool-aged travelers, and 3.2% of school-aged travelers were found to be eligible for MMR vaccination. However, 44.1% of eligible infants, 56.5% of eligible preschool-aged travelers, and 88.5% of eligible school-aged travelers did not undergo vaccination when seen by their providers.

The authors of the study noted that the most common reasons for nonvaccination were clinician decision and guardian refusal. “The findings suggest that opportunities exist for clinicians to provide pretravel MMR vaccination to US pediatric travelers and that additional education of clinicians and guardians may be needed,” they wrote.

Infectious Diseases Consultant discussed the implications of these findings further with lead study author Emily P. Hyle, MD, assistant professor of medicine at Harvard Medical School, and an infectious disease specialist in the Division of Infectious Diseases at Massachusetts General Hospital.

ID CON: We saw firsthand the importance of MMR vaccination in 2018 and 2019, when the United States experienced a resurgence of measles to the point where the United States almost lost its elimination status for measles. Could you discuss what factors, including undervaccination, led to this resurgence?

Dr Hyle: The biggest contributor to the resurgence of measles in the United States is a reduction in MMR vaccinations among some children. Overall, the national rates of MMR vaccination remain high, but there have been a rising number of families who decline vaccination based on religious or personal beliefs. Because measles is so incredibly contagious, it is essential to maintain exceptionally high vaccination rates (>94-95%) to prevent sustained transmission of measles within the United States. Even a small reduction in these high vaccination rates can have big implications. If one person with measles joins a community (after international travel, for instance), measles spreads rapidly among the unvaccinated.

ID CON: In your study, you and your colleagues concluded, “The findings suggest that opportunities exist for clinicians to provide pretravel MMR vaccination to US pediatric travelers and that additional education of clinicians and guardians may be needed.” Could you elaborate on this? What strategies may help bring MMR vaccination rates up?

Dr Hyle: Our study identified that many pediatric international travelers from the United States who attended pretravel clinics did not receive the MMR vaccination(s) that are recommended before departure. For US children, a first dose of MMR is routinely recommended at 12 to 15 months, followed by a second dose at 4 to 6 years; however, for children who are more likely to be exposed to measles (such as children who travel internationally), MMR vaccinations are recommended on an accelerated schedule. For infants aged 6 to 12 months, one dose of MMR is recommended (and then 2 doses on the routine schedule); for preschool-aged travelers aged 1 to 6 years, 2 doses of MMR are recommended prior to travel.

We found that 92% of infant travelers and 60% of preschool-aged travelers were eligible for MMR vaccination prior to departure, but 44% of eligible infant travelers and 59% of eligible preschool-aged travelers were not vaccinated with MMR at the pretravel clinic visit. We expected that a major reason for non-vaccination would be that guardians declined vaccination, which occurred in 36% of cases. But, we were surprised to find that 36% of eligible pediatric travelers were not vaccinated because the provider did not recommend it. Improving communication with both families and providers will be essential to improving MMR vaccination among pediatric international travelers prior to departure.

ID CON: In the context of the coronavirus disease 2019 (COVID-19) pandemic, what lessons can be learned from the recent resurgence of measles, especially when it comes to travel?

Dr Hyle: The resurgence of measles in the United States and globally highlights the challenges of access to care. MMR is a safe and effective vaccine, but the number of measles cases has surged worldwide over the past few years and is driven predominantly by reduced access to routine vaccinations in disrupted health care systems. In the United States and Europe, we have also seen a rise in vaccine refusal and vaccine hesitancy from parents and guardians. This means that international travelers over the past few years have had a greater risk of being exposed to measles during any international travel, resulting in more imported measles cases and outbreaks in the US.

If a vaccine is developed to prevent COVID-19, it will be important to recognize all of the operational challenges that are associated with widespread vaccination campaigns, as well as the need for provider, patient, and family education regarding risks and benefits of vaccination.

ID CON: What key takeaways do you hope to leave with infectious disease specialists on this topic?

Dr Hyle: The COVID-19 pandemic has created substantial challenges with attaining routine in-person medical care in the United States and internationally. I am extremely worried about the access of many children throughout the United States to routine childhood vaccinations because of the need to minimize office visits, which often include vaccinations. With any reduction in MMR vaccinations nationally, the United States would be more susceptible to prolonged measles outbreaks, which then would contribute additional stress to our health care systems and public health infrastructure.

Additionally, if a safe and effective vaccine to prevent COVID-19 disease is developed, it will be important to engage in community outreach and address concerns regarding vaccine safety and side effects.

ID CON: What is the next step in terms of future research in this area?

Dr Hyle: International travel has markedly declined in the setting of the COVID-19 pandemic. As the pandemic continues to evolve, we will need to study the risks of international travel for travelers and the communities to which they return, as well as effective approaches to reduce COVID-19 and measles transmissions among travelers and within communities.

—Christina Vogt

Hyle EP, Rao SR, Bangs AC, et al. Clinical practices for measles-mumps-rubella vaccination among US pediatric international travelers. JAMA Pediatr. 2020;174(2):e194515. doi:10.1001/jamapediatrics.2019.4515