U.S. Measles Outbreaks 2025-2026: Overview and Issues for Congress

As of September 24, 2026, the United States has seen the highest number of annual reported measles cases since 1991, according to Centers for Disease Control and Prevention (CDC) data. This 2026 total has already exceeded the 2025 total, which was also significantly higher than prior years. In 2000, the United States declared it had eliminated measles, meaning that no continuous spread had occurred in the United States across one year. CDC credited the measles elimination to a "highly effective vaccination program," as well as better measles control in the Americas region. The United States may lose its decades-long measles elimination status this year due to ongoing outbreaks.

Measles is a vaccine-preventable disease, meaning that the two-dose vaccine can protect against measles infection and disease. High measles vaccination rates (estimated 95% of the population and above) in a community can help establish herd immunity that limits the spread of the virus and protects those who cannot get vaccinated, including infants who are not yet eligible for vaccination and people with medical contraindications to measles vaccines.

About Measles

Measles, also referred to as rubeola, is a highly contagious virus that spreads from person to person through contact with respiratory and airborne droplets. It is characterized by a red rash that spreads from the hairline to the neck, torso, arms, legs, and feet. In addition to the rash, measles is often accompanied by a high fever, cough, and common complications like ear infections and diarrhea. More serious complications include pneumonia, encephalitis (swelling of the brain), long-term nervous system damage, and death from respiratory and neurologic complications. Measles complications are most common among children under five years of age and adults.

Prior to the vaccine's introduction in 1963, an estimated 3 to 4 million cases, 48,000 hospitalizations, and 500 deaths occurred annually in the United States due to measles. About 1,000 people annually developed chronic disabilities from brain swelling caused by measles. Nearly all children were infected with measles before age 15. From the introduction of the vaccine in 1963 to 2000, when measles was eliminated, the incidence (i.e., annual rate of cases) decreased by 99.9%.

No specific treatment is available for measles (e.g., pharmaceutical drug); instead, measles is treated by managing symptoms and preventing complications. The measles vaccine is the best available tool to protect against measles.

Measles Vaccines

The measles vaccine is available in two formulations: the combined FDA-licensed measles, mumps and rubella (MMR) vaccine and a combined measles, mumps, rubella, and varicella (MMRV) vaccine. Either vaccine is available as a two-dose series that establishes life-long immunity and is 97% effective at protecting against measles. The MMR/MMRV vaccines can cause mild side effects such as soreness, fever, rash, and temporary pain. Serious side effects are very rare and include conditions such as febrile seizures and anaphylaxis (allergic reaction). Numerous studies have found no causal link between MMR/MMRV vaccination and autism.

Recent Changes to Measles Vaccine Recommendations

CDC has generally recommended that all children receive two doses of the MMR/MMRV vaccines: one dose at 12-15 months of age and another at four to six years of age. However, there have been recent changes in related recommendations.

In 2010, the Advisory Committee on Immunization Practices (ACIP)—a committee that advises the CDC Director on U.S. vaccination policy—recommended, for children under four years of age, to use the MMRV vaccine instead of MMR only if the parent or caregiver expressed a preference for it. On June 9, 2025, the Department of Health and Human Services (HHS) Secretary removed all sitting ACIP members and subsequently appointed new members. In September 2025, the reconstituted committee recommended against use of the MMRV vaccine for children under four years of age, favoring separate MMR and varicella vaccinations. This recommendation change, as well as the appointment of the new ACIP members, has been stayed (i.e., blocked) by a U.S. district court order.

On August 10, 2026, President Trump issued Executive Order (EO) 14420, which set forth the Gold Standard Childhood Vaccine Recommendations. The order maintained the measles vaccine recommendation for all children but recognized that the MMR vaccine "should be administered in three separate single-disease shots" once such products become domestically available. The EO specified that to the extent feasible, such shots are to be administered at separate medical visits. EO 14420 then instructed departments and agencies to review these recommendations and "take any appropriate steps to advance them, to the fullest extent allowable by law."

To adhere to the EO's recommendations, vaccine manufacturers would need to submit new single-antigen measles vaccines for FDA licensure, which would require new large-scale clinical trials to test their safety and efficacy along with new manufacturing capacity. Vaccine manufacturers have reportedly stated that it could take as many as 10 years to develop new vaccines and have defended the safety and efficacy of existing vaccines. CDC's current webpage states that "no published scientific evidence shows any benefit in separating the combination MMR vaccine into three individual shots."

U.S. Measles Vaccination Rates

According to CDC data, 90.8% of children in the 2021-2022 birth cohort received the first recommended dose of the MMR/MMRV vaccine by 24 months of age; this vaccination coverage meets the Healthy People 2030 goal and has stayed relatively consistent over time.

In collaboration with states, CDC also tracks the proportion of kindergartners who received both doses of either the MMR or MMRV vaccine (hereinafter "MMR vaccine"). According to the latest data, 92.4% of kindergartners across 48 states and the District of Columbia received both doses of the MMR vaccination in the 2025-2026 school year. This total is a decrease from the previous peak in the 2019-2020 school year, where 95.2% of kindergartners were fully vaccinated.

MMR vaccination rates vary considerably across geographic areas, as illustrated in Figure 1, which shows MMR vaccination coverage among kindergartners for the 2025-2026 school year by state. These geographic differences are more pronounced at a local level. An analysis of county-level MMR vaccination rates (two doses) for the 2023-2024 school year (for 2,237 counties across 38 states with available data) found that many counties had kindergarten MMR vaccination rates below 83.5% and some have rates lower than 72%. Communities with low vaccination rates are particularly vulnerable to outbreaks.

Figure 1. MMR Vaccination Coverage Among Kindergarteners 2025-2026 School Year

Source: Figure developed by CRS using data from CDC's SchoolVaxView.

All states and D.C. require MMR vaccination for school attendance. Many states allow exemptions to these requirements, including medical exemptions and nonmedical religious and philosophical exemptions. Over the past five years, the proportion of kindergartners with vaccine exemptions has increased. During the 2025-2026 school year, a record high proportion of kindergarteners (4.2%) had a vaccine exemption, mostly nonmedical religious or philosophical exemptions.

2025-2026 Outbreaks

As of September 24, 2026, 3,659 confirmed measles cases were reported in the United States in 2026, the highest number of annual cases in 35 years (9,643 cases in 1991). In 2025, a total of 2,289 confirmed measles cases were reported. Among all reported cases in both years, over 92% of cases were in people who were unvaccinated or with unknown vaccination status, and over 9% of reported cases resulted in hospitalization. CDC reported three confirmed measles-associated deaths in 2025. Pennsylvania Department of Health has reported four measles-associated deaths in 2026. As of September 25, 2026, CDC's website lists one measles-associated death in 2026, which is to be updated as additional information becomes available and reviews are completed. The website also states that CDC is working to develop a standardized case definition for measles deaths for consistency across states.

Several recent analyses found that areas affected by measles outbreaks had comparatively low vaccination rates. For example, in the West Texas measles outbreak in 2025—one of the largest recent outbreaks—some of the affected counties had vaccination rates as low as 77.3% (for the two-dose series) among kindergartners for 2024-2025 school year. These data do not capture homeschooled students—reportedly many children in the affected area were homeschooled—and therefore the actual MMR vaccination rates for children in the region may have been lower. Another analysis of a measles outbreak in South Carolina from October 2025 through April 2026 examined vaccination rates at schools in the outbreak area and found that mean vaccination coverage (two doses of MMR vaccine) at schools exposed to the outbreak was 82.5%, compared with 91% for schools not exposed to the outbreak.

Selected Issues for Congress

Education and Messaging. The Trump Administration has issued varying messages regarding the MMR vaccine. For example, a March 2026 CDC press release stated, "The benefits of the MMR vaccine far outweigh the risks." Separately, the President suggested the MMR vaccine could be "quite lethal." Congress has previously enacted related laws; for example, P.L. 116-260 (Division BB, Title II, Section 311) directed a CDC public awareness campaign on the importance of vaccination. Congress may choose to revisit such laws, as well as their funding and implementation, or may take no action.

Vaccine Access. Virtually all U.S children have access to MMR vaccines, in large part because of federal requirements on most private health insurance plans and CDC's Vaccines for Children (VFC) program, which provides vaccines to children who are Medicaid-eligible, uninsured, underinsured, or American Indian/Alaska Native. However, CDC analyses have found that vaccination rates are lower among VFC-eligible children and children who live in poverty. Congress may examine programs to determine if further changes are needed for vaccine access.

Outbreak response. State, local, territorial, and tribal public health agencies lead responses to measles outbreaks in their communities. CDC provides support through ongoing grants and additional epidemiological and laboratory support, vaccines supplies, and educational resources. As of September 2026, CDC awarded $50 million in additional one-time funding to grantees for measles outbreak response. Congress may assess whether current funding and support are adequate.