Measles vaccines given long ago could be less effective now, doctors say

Amid the current measles outbreak in West Texas, doctors are warning that the protection provided by legacy measles vaccines may have worn off for some individuals. The measles vaccine was first introduced in 1968, and the MMR vaccine, which protects against measles, mumps, and rubella, was introduced in 1971. While the two-dose series of the MMR vaccine is typically effective in providing lifelong immunity for most people, there is a possibility that immunity can wane over time.

For adults who received both doses of the MMR vaccine as children, they are likely still protected unless they are in high-risk groups such as healthcare workers or travelers to outbreak areas. However, adults who were vaccinated for measles between 1963 and 1968 should check their vaccination history as a version of the vaccine used during that time was found to be less effective and was ultimately withdrawn. Additionally, individuals born before 1957 likely have natural immunity as they were likely exposed to measles before vaccines were available.

While studies show that antibody levels can decrease over time, actual cases of measles in fully vaccinated individuals remain rare. It is recommended that individuals concerned about their immunity levels can undergo a blood test to check their antibody levels. While there is no official recommendation for a third vaccine dose, individuals traveling to areas with measles outbreaks may benefit from a booster shot after consulting with a medical professional.

Dr. Marc Siegel, a clinical professor of medicine at NYU Langone Medical Center, stresses the importance of measles vaccinations, especially with the rising number of measles cases globally. He recommends that individuals traveling to outbreak areas should consider getting a measles titer test to measure their immunity levels and receive a booster if necessary.

As of 2025, a total of 164 cases of measles have been reported in the U.S., with the majority of cases in Texas. Other states reporting cases include New Mexico, California, Georgia, Kentucky, New Jersey, and Rhode Island. It is important for individuals to stay informed about their vaccination history and consider additional doses if necessary to protect themselves and prevent the spread of measles.