Importance Score: 75 / 100 🔴
When I registered for postgraduate studies at 53, I anticipated being the most senior student in the cohort. However, a specific admission prerequisite took me by surprise – a validated immunization record for measles, mumps, and rubella (MMR) and tetanus, certified by a physician.
Fortunately, I possessed my mother’s handwritten vaccine records and presented them to my general practitioner. “Excellent,” she remarked, examining the aged documents, which indicated a measles vaccination at 13 months and another at 10 years. “However, these are not official documents, so you will require a titer test.” A what?
My physician clarified that titer tests quantify antibody levels in the bloodstream. The results were unexpected. My rubella immunity was adequate, but mumps and measles antibody levels were deficient, necessitating an MMR vaccination before commencing on-campus activities.
Although a straightforward remedy, the situation remained in my thoughts. Why were my measles antibody titers low despite receiving two vaccine doses? Amidst record outbreaks this year – 607 in the US by April 3, 2025 – I questioned if older adults should be concerned about measles.
Vaccination between 1963 and 1967: Potential Considerations
According to Dr. Scott Roberts, an infectious disease expert at Yale Medicine, adults vaccinated against measles between 1963 and 1967 – as I was – may face increased vulnerability. During this period, Roberts explained, children received either an inactivated or a live measles vaccine. The inactivated version proved less effective and was discontinued in 1967.
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The Centers for Disease Control and Prevention (CDC) estimates that approximately 1 million individuals in the US received the inactivated vaccine between 1963 and 1967. (While tested in UK clinical trials, it was never widely adopted there.) My mother’s records indicated my second measles vaccine was live, but the initial dose, administered in late 1967, was likely inactivated, potentially explaining the low titer results.
Dr. Aniruddha Hazra, an infectious disease specialist at UChicago Medicine, advises that if you know you received the inactivated vaccine, or are uncertain about the type received in the 1960s, “obtain the MMR vaccine again. There is no risk in receiving the vaccination even if fully immunized.”
Adults can ascertain immunity through a titer test, as I did, but the test may be more costly than the MMR vaccine itself. “If you prefer to have titers checked first,” Hazra suggested, “discuss this with your healthcare provider.”
However, a low titer test result does not automatically imply susceptibility to infection. Dr. Robert Bednarczyk, an associate professor of global health and epidemiology at Emory University’s Rollins School of Public Health, clarified that even if vaccinated individuals lack detectable circulating antibodies, their immune systems likely retain memory cells capable of producing antibodies upon viral exposure.
Born Before 1957: Pre-Vaccine Era Considerations
Prior to the introduction of the measles vaccine in 1963, measles was a primary cause of mortality in children under five. Infection could lead to hearing impairment, deafness, or debilitating neurological complications. What are the current recommendations for adults born before the vaccine’s availability?
“Individuals born before 1957 were exposed to measles,” Hazra stated. “Based on this, the CDC and ACIP [Advisory Committee on Immunization Practices] have concluded that exposure or measles acquisition can be assumed, and measles immunity is considered lifelong.” Consequently, no additional vaccination is generally advised for this demographic.
Single or Double Dose MMR Vaccination?
The recommended number of MMR vaccine doses can be somewhat nuanced.
Until 1989, the CDC recommended a single MMR vaccine dose for children. Subsequently, a second MMR dose was advised to “enhance the immune response in individuals who did not fully respond to the initial dose,” Bednarczyk noted.
Currently, the CDC recommends two measles vaccine doses for children and “one or two” doses for adults, with the two-dose recommendation reserved for adults identified as high-risk, such as those in higher education, healthcare professions, or international travelers.
“A single dose is highly effective in measles prevention,” Bednarczyk stated. “This is pertinent, as many individuals born before the mid to late 1980s likely received only one MMR vaccine dose.” However, he added that those vaccinated before the two-dose recommendation benefited from high MMR vaccine adoption rates, significantly minimizing the risk of extensive measles outbreaks.
The vaccination landscape has shifted in recent years. Since the 2019-20 school year, vaccination rates among school children – targeted at 95% – have decreased considerably. According to KFF, a health policy non-profit organization, only 11 US states reported vaccination rates at or above 95% in the 2023-24 school year. Previous vaccination guidelines considered measles eradication in the US, Hazra explained. “All adults residing in the US should currently be considered high-risk,” he asserts, advocating for two live vaccine doses during their lifetime, except for adults born before 1957.
Dr. David Nguyen, an internal medicine and pediatric infectious disease expert at Rush University System for Health, shares a similar perspective. “If an adult received only one MMR vaccine prior to the two-dose recommendation, they should consider receiving a second dose.”
In the absence of formal CDC guidance for all adults, one point is clear: two live vaccine doses confer lasting immunity. “There is also no benefit to receiving more than two,” Hazra stated. For individuals who know they received two live vaccine doses, he confirms no recommendation for additional doses, even during outbreaks or international travel.
Duration of Measles Immunity: Does it Diminish?
Last month, Robert F. Kennedy Jr., then US health secretary nominee, stated in an interview that MMR vaccine immunity “diminishes 4.5% annually” and that “older individuals are essentially unprotected.”
“That is factually incorrect,” Hazra refuted. “If that were accurate, we would observe increased measles cases in vaccinated individuals.” Hazra emphasizes the importance of including older adults in measles protection discussions; they are more susceptible to potential measles infection complications, such as pneumonia. However, all experts consulted caution against widespread misinformation regarding the measles vaccine. “Antibody levels against the measles virus may decrease over time,” Bednarczyk acknowledges. “However, in cases observed thus far in 2025, only 3% had documented measles vaccination history.”
MMR Vaccine Side Effects: What to Expect
Bednarczyk reports “no significant differences in side effects for adults compared to children,” noting that they typically subside within a few days. “Many live vaccines generate a stronger immune response within 24-48 hours,” Hazra adds. “The body is initiating an immune response, requiring substantial energy expenditure.”
Common side effects include fever, injection site tenderness and inflammation, headache, muscle discomfort, fatigue, or a mild rash. “In infrequent instances,” Bednarczyk mentioned, “a temporary decrease in blood platelet levels may occur post-vaccination, which can also arise from measles virus infection itself.”
An individual infected with measles can transmit the disease to an average of 18 unvaccinated individuals, Bednarczyk explained, highlighting measles as one of the most contagious illnesses. (In comparison, individuals with seasonal influenza typically infect approximately two others.) “Airborne pathogens can persist for up to two hours,” Hazra added. “This longevity contributes significantly to its infectiousness.”
MMR vaccination is considerably less risky than developing natural immunity through infection. “Contracting measles disease carries the risk of subsequent complications,” Nguyen emphasized. These encompass subsequent measles infections due to “immune amnesia” and severe complications from measles-related encephalitis.
Individuals uncertain about their vaccination status should consult their healthcare provider regarding MMR vaccination or a titer test. Broad immunity within the US population is crucial for collective protection.