Many US Travelers Skip MMR Vaccination Before Overseas Trip

Diana Phillips

May 15, 2017

Many Americans traveling abroad are not immunized against the measles, putting themselves and those they come in contact with at unnecessary risk for infection, a study shows.

Although endemic measles was eliminated in the United States in 2000, the highly contagious virus is still common in many parts of the world, including some countries in Europe, Asia, the Pacific, and Africa, and can be imported into the United States by unvaccinated travelers.

As reported previously by Medscape Medical News, most measles cases in the United States can be traced to people who were not vaccinated against the virus or whose vaccination status is unknown.

To assess whether travelers understand the risk for measles infection, and to evaluate the reasons for nonvaccination among those who are aware that they are not fully immunized, Emily P. Hyle, MD, from Massachusetts General Hospital in Boston, and colleagues reviewed the medical records of 40,810 adults who received pretravel consultations at any 1 of 24 Global TravEpiNet (GTEN) clinical sites across the United States between 2009 and 2014.

The study findings are reported in an article published online May 15 in the Annals of Internal Medicine.

Of the full study population, 34,092 (84%) were considered immune to measles on the basis of providers' clinical assessments. Most of those deemed immune had a history of receiving two measles, mumps, rubella (MMR) vaccinations; others were positive for measles antibodies on serologic testing, had a history of measles illness, or were considered immune on the basis of provider judgment, the authors report.

More than half (53%) of the remaining vaccine-eligible travelers, excluding 106 in whom the MMR vaccine was contraindicated, were not vaccinated during the pretravel visit, according to the authors. The reason for nonvaccination in this population was most commonly (48%) traveler refusal, but provider decision (28%) and health system barriers (24%) were also cited.

The researchers looked more closely into why patients refused the vaccine and why providers decided not to vaccinate by reviewing data from 2012 and beyond, when such information was reported in the patient records. Nearly 75% of the eligible patients who refused vaccination in 2012 or later did so because they were not concerned about illness, the authors report.

With respect to providers' decision not to vaccinate, in nearly all of the cases (94%), "the provider thought the MMR was not indicated," they write, noting that only 6% of eligible patients were not recommended for vaccination because their provider believed there was not enough time before travel.

When health system barriers were cited as a reason for nonvaccination among eligible patients, "the predominant barrier was referral to another provider for vaccination," the authors write. It's possible that travelers were referred to another provider in an attempt to ensure records of vaccinations stay with primary care providers or to reduce costs associated with travel-related vaccines, which are not uniformly covered by insurers even when the same vaccinations are covered under routine care.

"Given the serious public health implications of undervaccination, strong consideration should be given to requiring insurers to cover MMR vaccination regardless of the site of delivery," the authors stress.

The majority of the eligible travelers (65%) who were not vaccinated, predominantly because of traveler refusal, were seen at GTEN sites in the South, "suggesting geographic variability in the understanding of measles and the benefits of MMR vaccination," the authors write.

The study findings "underscore the need for strategies to improve provider and traveler knowledge of measles as a travel-related illness and the need to increase pretravel uptake of the MMR vaccine," the authors write. This is especially important for communities with higher numbers of nonimmune individuals because of the increased transmission risk posed by an index case in such settings.

When it comes to efforts to increase MMR immunization rates, unvaccinated travelers are an "often-overlooked population," write Lori K. Handy, MD, from Thomas Jefferson University, and Paul A. Offit, MD, from the University of Pennsylvania in Philadelphia, in an accompanying editorial.   

"To prevent endemic measles from recurring in the United States, we must be vigilant about ensuring that travelers do not bring the virus back from overseas."

The study finding that most of the eligible travelers who refused vaccination did so because they were not concerned about illness suggests that many people do not understand the potential severity of measles or the implications of transmission, the editorialists write. "Exotic infections, such as malaria and yellow fever, preoccupy travelers; measles should be just as feared, and vaccination should be strongly encouraged, " they state. "Providers must play a role in helping travelers understand the seriousness of this infection."

If the importance of pretravel MMR vaccination is not well communicated or understood, according to the editorial writers, "our society is destined to be affected by imported cases of measles, leading to morbidity and mortality from this disease."

Dr Hyle reports grants from the National Institutes of Health and Centers for Disease Control and Prevention during the conduct of the study. One of the study coauthors, Rochelle P. Walensky, MD, reports grants from the National Institutes of Health during the conduct of the study. The editorial writers have disclosed no relevant financial relationships.

Ann Intern Med. Published online May 15, 2017. Abstract, Editorial

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