Public Release: 

Vaccines: Don't leave home without them

Many Americans traveling overseas at risk for measles, hepatitis A, studies suggest

Infectious Diseases Society of America

SAN DIEGO - While Americans should be fully vaccinated before travelling internationally to avoid infection with highly contagious diseases such as measles and hepatitis A, many are not, suggest two studies being presented at IDWeek 2015™. The findings suggest the lack of pretravel vaccination was a factor in illness outbreaks.

More than half of eligible Americans visiting a travel clinic prior to international travel did not receive the measles, mumps and rubella (MMR) vaccine as recommended, despite being at risk for measles, according to one study. Another study reports on a 2015 hepatitis A outbreak at a popular resort destination in Mexico which could have been avoided with proper vaccinations. Researchers in this study noted that exposure to contaminated food and water while travelling internationally is the most common way Americans become ill with this virus.

"Americans planning international travel should see their health care providers or visit a travel clinic four to six weeks before the trip to learn what vaccines are recommended before heading to their destinations," said Emily Hyle, MD, lead author of the measles vaccination study and Instructor at Harvard Medical School and Massachusetts General Hospital, Boston. "Many travelers don't realize their risk of exposure to infections and that many can be avoided with vaccination."

Measles Vaccination Study

A study of more than 40,000 U.S. travelers found that 16 percent were eligible for the MMR vaccine - meaning they were not immunized or under-immunized and were medically eligible - but fewer than half of them received the vaccine during pre-travel consultation, despite Centers for Disease Control and Prevention (CDC) guidelines. While continuous measles transmission was eliminated in the United States 15 years ago, it is a significant problem globally, with more than 20 million cases occurring annually. Americans who are not vaccinated risk getting sick with the measles if exposed, as well as bringing it back home and infecting others. Most of the measles outbreaks in this country have been caused by unvaccinated people being infected with measles overseas and traveling to the United States.

The research focused on 40,810 adults born after 1956 who received pre-travel consultations between 2009 and 2014 at 24 sites associated with Global TravEpiNet (GTEN), a -CDC-supported consortium of clinical sites that provide pre-travel health care. Of those adults, 6,612 (16 percent) were eligible for vaccination, but only 3,135 (47 percent) received the MMR vaccination before travel.

"Measles is one of the most contagious diseases in the world and even brief exposure can lead to infection," said Dr. Hyle. "Many travelers heading to developed countries, including those in Europe, might not realize that there are outbreaks of measles occurring in those areas, and they are at risk for becoming ill."

Measles can lead to pneumonia, brain swelling, hospitalization and occasionally, death.

Hepatitis A Vaccination Study

Uncommon in the United States, hepatitis A outbreaks are more likely to occur in areas with inadequate sanitation and limited access to clean water. U.S. travelers to these regions should take precautions by ensuring they are up to date on vaccination. Hepatitis A can lead to fever, nausea, exhaustion, jaundice and stomach pain.

Researchers reported on an outbreak of hepatitis A infection in Tulum, Mexico, a popular resort destination along the Caribbean Sea. They reported on 29 cases of acute heptitis A that occurred in Americans who traveled to Tulum between Jan. 5 and March 20, 2015. Of the patients, 17 (63 percent) stayed at one of nine resorts within a few miles of each other, 23 (79 percent) reported eating seafood and 16 (62 percent) said they ate ceviche, raw seafood cured in lime juice. None had received the hepatitis A vaccination prior to travel.

"Hepatitis A vaccination prior to travel is the most effective way to avoid infection, regardless of length of stay or quality of lodging," said Monique Foster, MD, MPH, lead author of the hepatitis A study, and Epidemic Intelligence Service Officer in the Division of Viral Hepatitis at CDC in Atlanta. "Travelers to areas where hepatitis A may be a problem should avoid consuming non-bottled water, uncooked fruit and vegetables, and undercooked meats, including raw fish and shellfish such as found in ceviche."


Other vaccinations may be recommended depending on the destination. For more information about vaccination and other health recommendations when traveling internationally, visit


  • Americans traveling internationally can reduce their risk of being infected with measles, hepatitis A and other diseases by being vaccinated before the trip.
  • One study found more than half of eligible Americans who visited a travel clinic did not get the recommended measles vaccine.
  • Unvaccinated Americans are at risk for measles infection while traveling, as the highly contagious disease is common worldwide.
  • Vaccination protects against hepatitis A, the cause of a 2015 outbreak in Mexico.

Co-authors of the measles study in addition to Dr. Hyle are Sowmya Rao, PhD, Boston University, Boston, M.A., Emily Jentes, PhD, MPH, and Amy Parker Fiebelkorn, MSN, MPH, of CDC, Stefan Hagmann, MD, of the Bronx Lebanon Hospital Center, Bronx, N.Y., and Rochelle Walensky, MD, MPH, Edward Ryan, MD and Regina LaRocque, MD, MPH, of Massachusetts General Hospital and Harvard Medical School.

Co-authors of the hepatitis A study in addition to Dr. Foster are Melissa Collier, MD, MPH, and Kathryn Spruit-McGoff, MSN, of CDC, Vasudha Reddy, MPH, of the New York City Department of Health & Mental Hygiene, N.Y., Jaclyn Skidmore, MSc, of the Rhode Island Department of Health, Providence, and Maureen Fonseca-Ford, MPH and Elsa Villarino, MD, MPH, of CDC.

About IDWeek

IDWeek 2015TM is the annual meeting of the Infectious Diseases Society of America (IDSA), the Society for Healthcare Epidemiology of America (SHEA), the HIV Medicine Association (HIVMA) and the Pediatric Infectious Diseases Society (PIDS). With the theme "Advancing Science, Improving Care," IDWeek features the latest science and bench-to-bedside approaches in prevention, diagnosis, treatment, and epidemiology of infectious diseases, including HIV, across the lifespan. IDWeek 2015 takes place October 7-11 at the San Diego Convention Center in San Diego. For more information, visit

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