Measles Outbreak: Do You Need Another Vaccine Shot?
With the ongoing measles outbreak that originated in Texas, many are wondering if a measles vaccine booster is necessary.
Measles, a highly contagious airborne illness, can lead to serious and potentially fatal complications. It is preventable with the MMR vaccine, typically given in two doses during childhood. While the U.S. had eliminated measles over two decades ago due to successful vaccination programs, declining vaccination rates have caused a resurgence. The CDC reported 285 measles cases in the U.S. in 2024. In the first four months of 2025, 800 cases have already been confirmed, with 96% occurring in unvaccinated individuals or those with unknown vaccination status.
In 2025, two unvaccinated individuals in Texas have died from measles complications. An unvaccinated adult in New Mexico tested positive for measles after death, although the official cause of death remains under investigation by the health department. Prior to this year, the last confirmed measles death in the U.S. occurred in 2015, according to the CDC.
Public health experts emphasize that vaccination is the best protection against measles. The MMR vaccine is considered safe and highly effective; the CDC states that two doses provide 97% protection. Dr. Ravi Jhaveri, a professor of pediatrics at Northwestern University Feinberg School of Medicine and division head of pediatric infectious diseases at Ann & Robert H. Lurie Children’s Hospital of Chicago, notes that individuals who did not receive the MMR vaccine as children can still get it as adults.
The CDC indicates that the MMR vaccine provides lifelong protection for most people, and a third dose is generally not recommended, even during an outbreak.
Dr. Jhaveri explains that “The vast majority of people with two doses are protected and do not get measles. Decades of experience show that two doses are safe and effective, and when vaccination rates are high, outbreaks are rare.”
However, booster shots are sometimes necessary for other diseases. Dr. Jhaveri explains that decisions about boosters depend on the virus’s genetic variability and the nature of immunity. For example, the flu and COVID-19 viruses change frequently, necessitating annual vaccinations. Tetanus boosters are needed because antibody levels decrease over time, and doctors often administer a booster after a high-risk exposure, such as a puncture wound. Measles, on the other hand, is genetically stable, and the two MMR vaccine doses “allow for you to have antibody levels that are high enough to protect you and also allow your cells to respond in case you are exposed, to prevent you from getting infected.”
Dr. Jhaveri notes that immune systems naturally weaken with age, potentially causing a slight decline in measles immunity. According to the CDC, about 3% of fully vaccinated individuals may still contract measles if exposed. However, vaccinated individuals who do get measles typically experience milder symptoms and are less likely to spread the disease compared to unvaccinated individuals. The CDC estimates that about 90% of unvaccinated people who are exposed to the virus will get measles.
One group that should consider revaccination includes those vaccinated before 1968 with an older, inactivated measles vaccine. The CDC recommends these individuals receive at least one dose of the current live attenuated vaccine because the older version, used from 1963 to 1967, was less effective.
Dr. Jhaveri stresses that the current outbreak primarily affects unvaccinated individuals, making a third dose unnecessary for those already vaccinated.
Dr. Jhaveri concludes, “The reason we’re seeing outbreaks now is because we have big pockets across our population that aren’t getting those two doses. Convincing vaccinated people to get another dose is not the priority; the focus should be on convincing those who don’t recognize the benefit of the two doses to get vaccinated.”