Walensky is the Bayer fellow in health and biotech at the American Academy in Berlin, a senior fellow at Harvard Kennedy School's Belfer Center for Science and International Affairs, and previously served as the 19th director of the CDC. Rader is the scientific director of the Innovation & Digital Health Accelerator at Boston Children's Hospital and an assistant professor in the Department of Anaesthesia at Harvard Medical School. Brownstein is the chief innovation officer of Boston Children's Hospital and the Robert and Dana Smith Family professor of pediatrics at Harvard Medical School.
A quarter-century ago, the United States celebrated a victory over measles, a highly contagious illness that once infected millions of American children each year. In 2000, after decades of hard work and widespread vaccination campaigns, public health officials declared measles eliminated in the U.S.
Today, that success is at risk. Fueled by growing mistrust in vaccine science and years of small but meaningful declines in routine childhood vaccinations, measles has made a troubling comeback. Less than three months through the year, the number of measles cases reported in 2025 has already exceeded all those recorded in 2024, as well as the annual case counts of all but three of the past 25 years. This year has also already documented two fatal cases of measles, the first U.S. deaths from the disease in over a decade. With vaccination rates declining, cases rising, and health care providers encountering their first cases of a disease once eliminated, we believe it is time to reevaluate national measles immunization guidelines, particularly to safeguard a vulnerable group still not fully accounted for in vaccination recommendations: our youngest infants.
The key to eliminating measles in the U.S. was widespread use of the measles vaccine, now delivered as part of the eponymously named MMR (measles, mumps, rubella) vaccine. First introduced in 1963, the measles vaccine essentially trains the immune system to recognize and fight measles by exposing it to a weakened version of the virus. Before the vaccine was widely available, measles killed between 400 and 500 children annually and hospitalized tens of thousands more. Thanks to the inability of the measles virus to effectively mutate, the vaccine is remarkably potent and durable. In children who receive one MMR dose, this vaccine is 93% effective at preventing measles. In children who receive two, that number jumps to 97%. The Texas Department of State Health Services has recorded 279 measles cases statewide in the ongoing outbreak. Prior MMR vaccination has been reported in only two of them.
Currently, the U.S. recommends that children receive their first MMR shot at 12 months and the second between ages 4 and 6, usually before starting kindergarten. Until about 6 months of age, infants receive some protection from antibodies passed from their mothers during pregnancy, but this immunity gradually fades, leaving a vulnerable gap between then and the first vaccine dose at 12 months. Doctors traditionally defer vaccinating infants younger than 12 months because their immune systems are not yet mature enough to develop lasting immunity. Until recently, this gap was not a major concern as measles exposure in the U.S. -- where it had been eliminated -- was extremely rare. Current guidelines allow an early -- and extra -- MMR dose between 6 and 12 months for infants traveling internationally or living directly within an outbreak area; two additional doses are still needed at 12 months and 4-6 years.
However, despite the numerous outbreaks in the U.S., there are no recommendations for infants traveling domestically or living near affected communities where, today, measles exposure may be considerably higher.
As measles regains a domestic foothold, infant vaccination guidelines should be expanded to protect all babies at risk of exposure, not just those traveling internationally. Measles is one of the most contagious known diseases, with each infected person typically spreading the disease to 12-18 additional others. The period between 6 months and 1 year of age is more than just a small gap in vaccine coverage. It is a critical time when protection against measles matters most. Young infants are especially vulnerable to the devastating effects of measles and face an increased risk of life-threatening complications -- some of which can emerge years after infection -- and even death.
Current guidelines prioritize early vaccination only for infants traveling to measles hot spots internationally, but fail to account for the growing threat of measles in our own communities. Past guidelines assumed that the greatest threat came from abroad, but today, a child is more likely to be exposed to measles in Paris, Texas, than in Paris, France. It's time to update our approach to both reflect this reality and do everything we can to reverse it. Updated guidelines should explicitly recommend an additional MMR vaccine dose for infants between the ages 6 and 12 months who are living in or traveling domestically to where cases of measles have been reported.
With measles resurging, we cannot rely on guidelines designed for an era when the virus was eliminated from American communities. Protecting infants demands policies that reflect today's reality: Measles outbreaks are happening here at home, placing the youngest and most vulnerable at unnecessary risk. Broadening early vaccination guidelines for infants facing higher exposure is a necessary step toward reclaiming our progress against a preventable disease and eliminating its spread once again.