U.S. health officials have expanded their vaccination guidance for international travellers as measles cases rise sharply around the world, including in Europe and the United States.

The Centers for Disease Control and Prevention (CDC) now recommends that all international travellers be vaccinated against measles, regardless of their destination. Previously, the CDC’s focus was on countries experiencing known outbreaks, but this latest update reflects growing concern over transmission during travel itself.

“This change is significant,” said Ashley Darcy-Mahoney, a health researcher at George Washington University’s School of Nursing. “We’re seeing a shift from localised outbreaks to transmission in transit. Measles is now being spread not only in outbreak zones but also on airplanes and during international travel.”

The updated guidance urges U.S. travellers aged 1 year and older to receive two doses of the measles-mumps-rubella (MMR) vaccine before departing the country. Infants between 6 and 11 months old should receive an early dose, aligning with recommendations from the European Centre for Disease Prevention and Control (ECDC), which has also advised travellers to ensure they are fully vaccinated.

Measles is a highly contagious viral disease that spreads through coughing, sneezing, and close contact. Even brief exposure in confined spaces—such as airports or airplanes—can result in infection, particularly among unvaccinated individuals.

The CDC’s change comes amid a troubling global resurgence of measles. So far in 2025, more than 1,000 measles cases have been reported across the U.S., while the European Union has logged over 5,500 cases. Health officials have attributed many of the new infections to gaps in immunisation, often exacerbated by misinformation and pandemic-related disruptions to routine childhood vaccinations.

In the U.S., a recent outbreak in Colorado was traced back to an international flight that landed in Denver, underscoring the risks of in-flight transmission and the importance of proactive immunisation.

Measles was declared eliminated in the U.S. in 2000, but periodic outbreaks have occurred in recent years, often linked to unvaccinated travellers bringing the virus back from abroad.

Public health experts stress that maintaining high vaccination coverage is key to preventing further spread. The MMR vaccine is safe and highly effective, providing lifelong protection in most individuals after two doses.

“Given the rise in global travel and measles cases, the updated CDC guidance is a timely reminder that vaccination remains one of our strongest tools to protect public health,” Darcy-Mahoney said.