Measles, Vaccine Hesitancy, and the ACIP

Kenny Lin, MD, MPH
Posted on March 24, 2025

As of March 20, 2025, 17 states had confirmed a total of 378 measles infections, with 351 cases associated with an ongoing outbreak in West Texas and New Mexico that began in late January. 64 people (17%) have been hospitalized for serious illnesses, and one child and one adult have died. For comparison, there were 285 cases of measles in the United States in 2024, and there have already been more reported cases than in all but 3 years since 2000. In a 2024 AFP editorial, Dr. Doug Campos-Outcalt reviewed best practices for diagnosis and prevention of measles. Of note, “a person with measles is infectious 4 days before through 4 days after the appearance of the [erythematous, maculopapular] rash.”

Increasing vaccine hesitancy has depressed measles, mumps, and rubella (MMR) vaccination rates in the affected jurisdictions, making more people vulnerable to the highly contagious illness. Parents may refuse vaccinations for their children due to concerns about adverse effects, such as the repeatedly debunked myth that MMR increases the risk of autism. (Studies show a 4 in 10,000 risk of a febrile seizure after receiving MMR at 12 to 15 months of age, considerably lower than the risk associated with measles infection.) Although the American Academy of Family Physicians and the American Academy of Pediatrics discourage nonmedical exemptions from childhood immunizations required for daycare or school attendance, “philosophical” or religious exemption policies have been increasing in the United States. In West Virginia, where the last reported case of measles was in 2009, physician advocacy groups successfully petitioned the governor to veto a 2024 bill passed by the state legislature that would have allowed private and parochial schools to opt out of state immunization requirements.

Currently, infants 6 to 11 months of age are recommended to receive an early MMR dose before international travel. In a recent JAMA Viewpoint, former Centers for Disease Control and Prevention (CDC) director Rochelle Walensky, MD, MPH, and colleagues proposed “updating the existing recommendation for an additional early MMR dose to infants aged 6 to 11 months traveling to any region with increased probability of measles exposure, whether international or domestic.” Although several federal agencies play a role in vaccine development and use, the CDC’s Advisory Committee on Immunization Practices (ACIP) has been the authoritative source of vaccine recommendations since its formation in 1964. Members of this independent committee are required to disclose financial conflicts of interest and recuse themselves from deliberations and votes about a vaccine, its potential competitors, and any other products of the company that makes the vaccine. An investigation by the journal Science concluded that contrary to accusations by leaders of antivaccine groups, there was “no sign that [ACIP] vaccine advisors are beholden to industry.” After the ACIP’s February 2025 meeting was postponed for unclear reasons, the CDC has announced that the committee will meet next month. According to the Federal Register notice, the agenda includes recommendation votes on meningococcal vaccines, chikungunya vaccines, and RSV vaccines for adults, as well as “an update on the current [Texas/New Mexico] measles outbreak.”