• Posted May 5, 2026

US on the Brink of Losing Measles-free Status, Study Warns

The United States is moving quickly toward losing its status as a measles-free nation, a new study says.

The nation has missed four of seven markers set by the U.S. Centers for Disease Control and Prevention (CDC) after experts declared measles eradicated in 2000, researchers report in The Lancet.

These include a surge in measles cases, the spread of outbreaks across the nation, measles cases spreading internally rather than coming from abroad and heightened infection risk from sick people.

Worse, the remaining three markers are at risk – indicating that measles could once again become a part of day-to-day life in America, researchers said.

“It appears highly likely that the USA will lose its measles elimination status in 2026,” concluded the research team led by Dr. Anne Bischops, a pediatrician and postdoctoral research fellow at Boston Children’s Hospital.

The reintroduction of measles into the U.S. would have a devastating effect on the health of America’s children, said senior researcher Maimuna Majumder, a scholar in the Computational Health Informatics Program at Boston Children’s Hospital.

Severe measles infections can cause life-threatening pneumonia or encephalitis, according to the World Health Organization. Infections also can cause lasting damage to children’s vision or hearing.

“A measles infection even when cleared can result in lifelong problems,” Majumder said in a news release. “Babies less than a year old are among those at greatest risk for severe complications, and the full impact on children exposed during the current outbreak may only show up years later.”

The latest string of U.S. outbreaks began in Texas in January 2025, researchers said in background notes. Since then, the outbreaks have spread to 45 states.

For the new study, researchers compared what’s been happening in the U.S. to the seven measles elimination warning markers set by the CDC’s National Immunization Program.

Results showed that four of these indicators are in the red:

• Low number of cases with a cutoff of less than one case per 10 million people: The U.S. had about 93 cases per 10 million people as of early 2026, far exceeding this limit.

• Most of the measles cases should come from abroad rather than from internal spread: Only 6% to 7% of measles cases since early 2025 have arrived from abroad, meaning most cases involve Americans infecting other Americans.

• A limited number of around four outbreaks per year with no more than about six cases each: Last year in the U.S., 48 outbreaks resulted in more than 2,000 cases. That’s continued into this year, as 19 known outbreaks have already resulted in more than 1,600 cases.

• A level of transmission less than one, meaning one infected person spreads measles to fewer than one other person on average: The U.S. has exceeded this rate more than 75% of the time since early 2025.

Worse, the remaining three indicators are showing signs of weakening:

• The U.S. has four weeks in a row where all infections come from abroad: Since the first infection in January 2025, the U.S. hasn’t gone four weeks without infections, and overall 90% of cases have been acquired internally.

• Herd immunity through vaccination: An estimated 95% of people need to receive two doses of the measles vaccine to achieve herd immunity. The average vaccination rate of U.S. kindergartners in last school year was 92%.

• Measles cases don’t share a common viral strain: Preliminary data show that the majority of cases share the same viral strain and are likely part of the same transmission chain.

“Declining vaccination rates have already been a warning sign that measles could return,” Bischops said.

These results could bode ill for an upcoming meeting of the Pan American Health Organization’s expert panel on infectious disease. 

At its November meeting, that panel is to reevaluate the United States’ measles elimination status. Canada lost its elimination status in November 2025, researchers noted.

“Strengthening vaccination efforts, reducing exemption rates and interrupting ongoing local transmission will be essential to reverse this trajectory,” the researchers said.

More information

The U.S. Centers for Disease Control and Prevention has more about measles.

SOURCES: Boston Children's Hospital, news release, April 30, 2026; The Lancet, April 30, 2026