For those vaccinated for measles decades ago, protections may now be exhausted.
Among the current outbreak of measles in western Texas, among cases reported in New Mexico, New Jersey and several other states, some doctors have warned about the possibility that legacy vaccines may become less effective over time.
Measles is a highly contagious virus for people who have never been infected or vaccinated before, and can be transmitted up to 90%.
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The measles vaccine was first introduced in 1968. Three years later, in 1971, the MMR vaccine debuted, offering three parts of protection against measles, mumps and rubella.
Some doctors have warned about the possibility that legacy vaccines may become less effective over time. (istock)
Decades after the release of the MMR vaccine, in 2000 it was declared that measles had been removed in the United States.
“The standard recommendation from health authorities like the CDC is a two-dose series of MMR vaccines,” Dr. Nicole Saphier, a contributor to Fox News Medical, told Fox News Digital.
“For most people, these two doses provide lifelong immunity. They are about 97% effective against measles.”
Who needs another vaccine?
According to Saffier, who practices in New York, the question of whether someone should take another measles vaccine depends on several factors, including the history of the vaccine, age, and health status.
“If you’re an adult who got both doses as a child, you’re probably fine unless boosters are considered by high-risk groups (such as healthcare workers or travelers to outbreak areas),” she said.
“Adults who were vaccinated for measles between 1963 and 1968 should check the history of vaccinations.”
Doctors say people born before 1957 are likely to have natural immunity, as they are likely exposed to measles before the vaccine became available.
“Adults who were vaccinated for measles between 1963 and 1968 need to check the history of the vaccine to determine which vaccine they received,” advised Saphier.
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“During that time, a version of the vaccine using the inactivated virus was available, not as effective and was eventually withdrawn.”
Research shows that antibody levels can decline over decades, but actual cases of measles in fully vaccinated people remain rare, Saffie added.
Research shows that antibody levels can decline over decades, but actual cases of measles in fully vaccinated people remain rare. (istock)
“Hard data doesn’t mean people need a third shot on a daily basis, but if you’re worried, you can check your antibody levels with a blood test,” she said.
“Like everything about medicine, vaccinations have rare risks and there is a substantial risk of not getting vaccinated.”
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Each person’s situation is different and after a thorough conversation with a trusted medical team, Saffie added.
Dr. Marc Siegel, professor of clinical medicine at Nyu Langone Medical Center and contributor to Fox News Medical, highlighted the importance of measles vaccination.
The measles vaccine was first introduced in 1968. Three years later, in 1971, the MMR vaccine debuted, offering three parts of protection against measles, mumps and rubella. (istock)
For those traveling to areas where measles outbreaks are occurring, he recommends seeing a doctor for a “titer test” for measles and getting a booster if he is not showing immunity. (The Fiter test measures an individual’s immune level against the virus.)
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“This isn’t an official proposal yet, but I check the titers of measles in many patients. If they are low, I might give them a booster as a precaution,” Siegel said.
MMR is a live viral vaccine that cannot be administered to pregnant women or immunocompromised people, doctors noted.
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So far, in 2025, a total of 164 cases of measles have been reported in the United States, according to data from the Centers for Disease Control and Prevention (CDC).
The majority of them (140) are in Texas. Nine cases have been reported in New Mexico, with the rest in California, Georgia, Kentucky, New Jersey and Rhode Island.
