Measles, HAV vaccination rates low among US international travelers

Issue: November 2015

SAN DIEGO — Many Americans do not receive measles-mumps-rubella or hepatitis A vaccines before traveling overseas despite CDC guidelines that recommend international travelers be fully vaccinated against these diseases, according to two studies presented at IDWeek 2015.

“Many travelers don’t realize their risk of exposure to infections and that many can be avoided with vaccination,” Emily Hyle, MD, instructor at Harvard Medical School and Massachusetts General Hospital, said in a press release.

Emily Hyle

During a presentation, Hyle said most measles outbreaks in the United States originate from Americans who were infected while traveling abroad. To determine the measles immunity status of international travelers from the U.S. and their reasons for not getting vaccinated, Hyle and colleagues reviewed data collected from 40,817 adults during pre-travel consultations at one of 24 CDC-sponsored Global TravEpiNet sites between 2009 and 2014.

Sixteen percent of the participants (n = 6,612) had no history or specified immunity to measles or did not receive two MMR vaccines before the consultation and were eligible to receive the vaccine. The researchers wrote, however, that just 47% of these participants were vaccinated during the consultation. The decision not to vaccinate was divided almost evenly between providers (52%) and patients (48%). Most providers either referred the participants to a primary health care provider or did not indicate the vaccination status. A majority of the participants opted out of the MMR vaccine because they were not concerned about the risk for infection.

“It’s essential to remember that measles is one of the most contagious diseases in the world with an over 90% infection rate among those who are unvaccinated without a single exposure to measles,” Hyle said during her presentation. “If somebody with measles walks into the room, measles infection remains in that room for up to 2 hours, so it’s incredibly contagious and you wouldn’t necessarily know that you were exposed.”

Susan McLellan, MD, from Tulane University, added that measles is a concern in developed parts of the world that many travelers may not suspect, such as Paris and other European cities.

Susan McLellan

“An unvaccinated or a nonimmune traveler returning from a measles-endemic country is more dangerous to the general population than someone returning from an Ebola-infected country because the risk that they will transmit disease to somebody who will get very sick from it is much higher than the risk of an asymptomatic traveler from an Ebola-infected country will do so,” McLellan said during the presentation.

Monique Foster, MD, MPH, epidemic intelligence service officer for the CDC’s division of viral hepatitis, and colleagues voiced similar concerns regarding low hepatitis A vaccination rates among international travelers. In April, the New York City and Rhode Island health departments reported acute hepatitis A cases among patients returning from Tulum, Mexico.

“The most common risk factor for prime hepatitis A infection is travel, usually through ingestion of contaminated food and water in an endemic country,” Foster said during the presentation. “Despite this, previous studies have shown only 13% of travelers have completed their HAV vaccination prior to departure.”

During their investigation, Foster and colleagues identified 30 patients from 12 states with acute hepatitis A who traveled to Tulum between Jan. 5 and March 20. Seventeen patients reported staying at one of nine resorts located within 4 miles of each other. Although the source of the outbreak was undetermined, Foster said about 62% of the patients reported consuming ceviche, a raw seafood cured in lime or lemon juice. Ten patients consumed restaurant seafood at the resorts. None of the patients was confirmed to be vaccinated against hepatitis A before traveling.

Monique Foster

“Hepatitis A vaccination prior to travel is the most effective way to avoid infection, regardless of length of stay or quality of lodging,” Foster said in a press release. “Travelers to areas where hepatitis A may be a problem should avoid consuming nonbottled water, uncooked fruit and vegetables, and undercooked meats, including raw fish and shellfish such as found in ceviche.”

Foster and colleagues concluded that the hepatitis A outbreak may have been averted if the patients were vaccinated. – by Stephanie Viguers

Reference:

Foster M, et al. Abstract 1049. Presented at: IDWeek; Oct. 7-11, 2015; San Diego.

Hyle E, at al. Abstract 113. Presented at: IDWeek; Oct. 7-11, 2015; San Diego.

Disclosure: The researchers report no relevant financial disclosures.