The U.S. government has expanded its health recommendations for international travelers, urging all American citizens to get vaccinated against measles before traveling, regardless of their destination. The update, published by the Centers for Disease Control and Prevention (CDC), responds to a rise in cases in 2025 and the risk of virus transmission during flights or at airports.
- What Does the CDC’s New Travel Advisory Say About Measles?
- Who Should Get Vaccinated Against Measles Before Traveling Abroad?
- Why Have Measles Cases Increased in the U.S., and What Is Their Connection to Travel?
- How Effective Is the MMR Vaccine, and What Is Its Availability?
- What Happens If an Unvaccinated Person Wants to Travel?
- What Is the International Context of Measles Outbreaks?
The warning includes revised guidance for people of all ages. It recommends that citizens 12 months and older have two doses of the MMR vaccine (measles, mumps, and rubella), and that infants between 6 and 11 months receive an early dose if they are leaving the country. These guidelines were officially published on May 31 on the CDC’s website.
According to CDC data, the U.S. has recorded over 1,000 measles cases so far in 2025. This figure represents an increase compared to previous years and has been partly linked to unvaccinated individuals who contracted the virus abroad and introduced it to the country through international flights. Most infections have occurred among people without vaccination records or with incomplete immunization schedules.
What Does the CDC’s New Travel Advisory Say About Measles?
The guidance published by the CDC states that all individuals over 1 year old should have received two doses of the MMR vaccine before traveling outside the country. This recommendation applies regardless of the destination, even if there are no active measles outbreaks in that region. For infants between 6 and 11 months, the CDC recommends an early dose, administered at least two weeks before travel.
The agency notes that exposure to measles can occur not only in the countries visited but also during transit at airports, on airplanes, and at transportation hubs. The update marks a change from previous recommendations, which only emphasized vaccination for those traveling to countries with active outbreaks.
Who Should Get Vaccinated Against Measles Before Traveling Abroad?
According to the CDC, the following people should consider getting vaccinated or reviewing their immunization schedule:
- Children 6 to 11 months old traveling internationally: one dose of MMR.
- People 12 months and older without proof of immunity: two doses of MMR, separated by at least 28 days.
- People born before 1957: generally considered immune, but should consult a healthcare professional if they lack documentation.
The MMR vaccine is part of the routine childhood vaccination schedule in the U.S. However, since the COVID-19 pandemic, immunization rates have slightly declined, increasing the risk of resurgence of diseases like measles, according to the CDC in its epidemiological surveillance bulletin.
Why Have Measles Cases Increased in the U.S., and What Is Their Connection to Travel?
Ashley Darcy-Mahoney, a researcher at the George Washington University School of Nursing, explained that measles is no longer spreading only in local communities but also during transit. “We are seeing a shift from localized outbreaks to transmission during transit,” she said. In May 2025, an outbreak in Colorado was linked to an international flight that landed in Denver.
The CDC states that measles can be transmitted from four days before the onset of the rash until four days after, meaning infected individuals without visible symptoms can spread the virus at airports or on airplanes. Measles is one of the most contagious diseases: it can be transmitted through the air and remain active in an enclosed space for up to two hours after an infected person has left, according to the World Health Organization (WHO).
How Effective Is the MMR Vaccine, and What Is Its Availability?
The MMR vaccine has proven to be 97% effective when the two recommended doses are administered, according to the CDC. The vaccine is distributed free of charge or at low cost as part of the National Childhood Vaccination Program and is also available at private clinics and authorized health centers. However, anti-vaccine movements and the spread of misinformation have led to a gradual decline in the acceptance of this immunization in some sectors of the population.
In Texas, for example, the State Department of Public Health confirmed in May that it is facing one of the largest outbreaks since 2019. At the same time, state legislators were debating a bill to expand school vaccination exemptions. If approved, this legislation would make it easier to refuse immunization for personal reasons.
What Happens If an Unvaccinated Person Wants to Travel?
The CDC recommends that travelers without proof of vaccination or documented immunity get vaccinated at least two weeks before their travel date. For those who cannot receive the vaccine for medical reasons, such as immunosuppression, it is suggested to avoid international travel until they can obtain the necessary protection or consider destinations with low virus circulation, in consultation with a healthcare professional.
The U.S. Department of State has also updated its travel recommendations in line with this guidance, though there are currently no immigration restrictions or mandatory vaccination requirements for re-entering the country. However, the CDC reiterates that individuals with fever, cough, or rash should refrain from traveling until an active infection is ruled out.
What Is the International Context of Measles Outbreaks?
The World Health Organization reported a 30% global increase in measles cases in 2024, with significant outbreaks in Eastern Europe, Central Asia, and Sub-Saharan Africa. According to the WHO, the rise is linked to the interruption of vaccination campaigns during the COVID-19 pandemic, insecurity in conflict zones, and low investment in primary healthcare systems.
The U.S. Department of Transportation reported that international travel levels have returned to figures similar to those in 2019, which, according to the CDC, represents an increased risk for the reintroduction of preventable diseases. Health authorities urge healthcare professionals to reinforce the verification of their patients’ vaccination status before any travel outside the country.
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