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

For those who were vaccinated for measles many decades ago, there's a chance the protection has worn off by now.

The measles vaccine was first introduced in 1968. Three years later, in 1971, the MMR vaccine made its debut, providing a trifecta of protection against measles, mumps and rubella.

A couple of decades after the release of the MMR vaccine, measles was declared eliminated in the U.S. in 2000. 

"The standard recommendation from health authorities like the CDC is a two-dose series of the MMR vaccine," Fox News medical contributor Dr. Nicole Saphier told Fox News Digital.

"If you're an adult who got both doses as a kid, you're likely fine unless you're in a high-risk group - such as healthcare workers or travelers to outbreak areas - where a booster might be considered," she said.

People born before 1957 presumably have natural immunity, as they were likely exposed to measles before vaccines became available, according to the doctor.

"Adults who were vaccinated for measles between 1963 and 1968 should check their vaccination history to determine which vaccine they received," Saphier advised. 

Studies show that antibody levels can wane over decades, but actual measles cases in fully vaccinated people remain rare, Saphier added.

"No hard data says people need a third shot routinely, but if you're worried, a blood test can check your antibody levels," she said.

"As with everything in medicine, there are rare risks to vaccinating and substantial risks to not vaccinating." 

Each person's situation is different and should be weighed carefully after a thorough conversation with a trusted medical team, Saphier added.

Dr. Marc Siegel, clinical professor of medicine at NYU Langone Medical Center and a Fox News medical contributor, also emphasized the importance of measles vaccinations - "particularly with the number of circulating measles cases and underimmunized people coming into the U.S. at a time when there is a big measles surge around the world."

"This is not yet an official suggestion anywhere, but I do check measles titers in many of my patients, and if they are low, I may give a booster as a precaution," Siegel said.

So far in 2025, a total of 164 cases of measles have been reported in the U.S., according to data from the Centers for Disease Control and Prevention (CDC).

A vast majority of those (140) are in Texas. Nine cases have been reported in New Mexico, with the remainder in California, Georgia, Kentucky, New Jersey and Rhode Island.