US may lose measles elimination status after outbreaks spread to 45 states
By Vanessa McMains, Children's Hospital
Boston
 |
| The Onion |
After public health experts declared measles eliminated in the U.S. in 2000, the U.S. Centers for Disease Control and Prevention (CDC) established seven indicators of measles elimination status to ensure that the country remained on track.
Now, analyzing these same indicators, Boston
Children's Hospital researchers find that the U.S. has missed four of the seven
criteria, with the others at risk. These findings are published in The Lancet.
The researchers who performed the analysis included Maimuna
Majumder, Ph.D., MPH, the Inaugural Peter Szolovits Distinguished Scholar in
the Computational Health Informatics Program at Boston Children's, and their
postdoctoral research fellow Anne Bischops, MD, a pediatrician and German
National Academy of Sciences Leopoldina Fellow. The team evaluated the number
of U.S. measles cases, outbreaks, their origination, and the levels of
transmission. Their results suggest that measles is making a comeback in the
U.S., spreading continuously for more than a year.
The latest string of U.S. outbreaks began in Texas in
January 2025. Since then, outbreaks have spread to 45 states. When the U.S. was
last recertified for measles elimination status in 2011, the country achieved
all the measles
elimination indicators established by the CDC's National Immunization
Program. But this year, according to this new research, most of the indicators
are in the red.
Missed indicators of measles elimination status
- Low
number of cases with a cutoff of less than one case per 10 million people.
As of early 2026, the U.S. had about 93 cases per 10 million people,
exceeding this limit.
- Most
of the measles cases should come from abroad rather than from internal
spread. Since the start of 2025, only 6–7% of the measles
cases have come from abroad, meaning most cases derive from
within the U.S.
- A
limited number of outbreaks (a cutoff of approximately four) with no more
than about six cases each. Last year in the U.S., 48 outbreaks resulted in
more than 2,000 cases. And in early 2026, at least 19 outbreaks have
already resulted in more than 1,600 cases.
- A
level of transmission less than one, meaning one infected person only
spreads measles to fewer than one other person on average. The U.S. exceeded
this rate more than 75% of the time since early 2025.
Indicators at risk
- The
country achieves four weeks with all infections deriving from outside the
U.S. Since the first infection in January 2025, the U.S. hasn't gone four
weeks without infections with 90% of cases acquired here.
- Herd
immunity through vaccination. An estimated 95% of people need to receive
two doses of the measles vaccine to achieve herd immunity, typically given
as part of the MMR (measles, mumps, and rubella) vaccine. However, the
U.S. average vaccination
rate of kindergartners in the 2024–2025 school year was 92%,
meaning this indicator is at high risk. In Texas, for example, vaccine
rates range as low as 79% to 90%, according to an earlier study from the team.
- Measles
cases don't share a common viral strain. From ongoing genetic
analyses, 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," said Bischops. "However,
losing status would be a clear and very concerning indicator."
The researchers believe these findings make a strong case
for vaccinating children to protect them from a young age.
"Viral infections aren't all benign and a measles
infection, even when cleared, can result in lifelong problems," said
Majumder. "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."
These data aim to provide insights/an early warning
framework ahead of a meeting of the Pan American Health Organization's expert
panel in November 2026 to reevaluate the U.S.'s measles elimination status.
Publication details
Will the USA lose its measles elimination status?, The
Lancet (2026).
