More than half of eligible US travelers not receiving measles immunization

"Measles has been eliminated in the U.S. since 2000, which means that all measles cases in the country can be traced back to an imported case -- either a foreign visitor or a U.S. resident returning from international travel," says Emily Hyle, MD, MSc, of the MGH Division of Infectious Diseases, lead and corresponding author of the report in Annals of Internal Medicine. "Since more than 60 percent of the measles importations into the country are due to returning U.S. travelers, increasing the number of travelers who are immune to measles will reduce the number of measles cases."

The Advisory Committee on Immunization Practices recommends two documented doses of the MMR vaccine for adult travelers without evidence of measles immunity. Such evidence includes a positive blood test for antibodies to the measles virus, a documented previous case of measles, or the individual's being born before 1957 when measles infection was extremely common.

The current study analyzed data from 24 Global TravEpiNet clinics that provide pre-travel health advice and vaccinations. These consultations use online questionnaires through which travelers indicate information on their current health, medical history and destination, and providers indicate the advice and services that were provided, including vaccinations.

In regard to the MMR vaccine, the questionnaires require providers to indicate the reasons that a patient was determined to be immune and to consider vaccination for those not considered immune. Unless there was a medical reason against MMR vaccination, such individuals were categorized as vaccine-eligible. When eligible patients were not vaccinated, providers needed to select one of these explanations: traveler refusal, vaccine not indicated for this patient or itinerary, insufficient time for vaccination before departure, vaccine unavailable at clinic, or referral for vaccination to another provider. Beginning in 2012, providers also indicated one of the following reasons that a traveler declined vaccination: concern about vaccine safety, concern about vaccine costs or lack of concern about contracting the vaccine-preventable illness.

Among more than 40,800 patients born after 1956 and seen for pre-travel consultation at Global TravEpiNet clinics from 2009 through 2014, 84 percent were determined to be immune to measles, primarily because of a history of two MMR vaccinations. Of the 6,612 remaining vaccine-eligible individuals, 3,477 (53 percent) were not vaccinated during the clinic visit. In 48 percent of those instances, the traveler refused vaccination. In 28 percent of consultations, providers decided not to suggest MMR vaccination; and in 24 percent, they referred the traveler to another provider for vaccination. Travelers refusing the MMR vaccine indicated a lack of concern about measles 74 percent of the time, concerns about vaccine safety 20 percent of the time, and concerns about costs 6 percent of the time.

"It was surprising to see such a high number of missed opportunities for MMR vaccination, even at these specialized pre-travel consultations, but our results also suggest ways to improve the rate of MMR immunization among eligible travelers," says Hyle. "We can definitely improve how often providers specializing in pre-travel medical advice offer MMR vaccine to eligible travelers and encourage clear discussions with patients about the risks of contracting measles and of spreading the disease after their return to the U.S."

Senior author Regina LaRocque, MD, MPH, explains, "Measles is one of the most infectious diseases known -- 90 percent of people who are not immune will contract measles from an even-minimal exposure to someone who is infected. A single case of measles can spark a major outbreak, especially in communities were many people are not immune. Even though a case of measles can be limited to fever, rash and cough, many cases can be severe and require hospitalization. Getting immunized for measles prior to travel helps to protect everyone in the U.S. -- in particular people who are immunosuppressed and babies too young to be immunized."