“As a vaccine, it’s super effective,” Dr. Moody tells SELF. “We think that once you’ve got immunity, it probably does last for the rest of your life.” But there are some potential reasons immunity may weaken a tad over time. First, most of us have had a total lack of exposure to the measles virus since vaccine coverage became widespread. “We know from things like chickenpox that when you are exposed, you get a little boost to keep up your immunity,” Dr. Moody explains. “Now that we don’t have as much measles circulating in the country, that might not happen.” To be clear, this doesn’t mean your immunity is going to eventually disappear, just that we may not be getting that additional exposure-based immunity anymore.
Also, immune function in general declines with age, Dr. Moody says. The immune system just doesn’t stay as strong or efficient as we get older, which is part of why elderly populations are at a higher risk of getting seriously ill from things like RSV, COVID-19, and the flu.
Can you test for measles immunity?
In short, yes. An antibody titer test is a blood test that can check your immunity to the measles virus. It’s available via your doctor or a technician at a pharmacy like CVS, though you may need to pay out of pocket for it.
However, Dr. Moody notes that antibodies are only one part of the picture. “We don’t really think the antibodies themselves are protecting you against measles,” he says. “It’s probably a T-cell response.” T-cells are white blood cells that fight germs and protect you from disease. When you have the measles or get the vaccine, for example, a number of these cells detect the virus and then adapt. Their sole purpose from that moment forward is to remember that specific virus and fight it off if you’re exposed to it again in the future. T-cells also help direct another type of immune cell (B-cells) to create antibodies, which are proteins that bind to the antigen and neutralize it, or prevent it from invading healthy cells and causing infection.
“The antibody test is a nice surrogate for [overall immunity], but it doesn’t tell you if the antibodies have gone away that the T-cell response has too,” Dr. Moody explains. However, testing for T-cells is harder to do and roll out at scale, he adds, so it’s not typically done for this purpose.
So yes, you could go and get a measles antibody test. But “it’s sometimes easier to just get the vaccine and be done with it,” says Dr. Moody.
How to know if you might need a measles booster
Hearing about an outbreak can be nerve-wracking, but as long as you are up-to-date on your recommended shots, experts say you should feel confident that you’re well protected.
Overall, “it’s extraordinarily rare” to get the measles if you’ve been fully vaccinated, Thomas Russo, MD, chief of the division of infectious diseases at the University at Buffalo in New York, tells SELF. The Centers for Disease Control and Prevention estimates that about 3 in 100 people who receive two doses of the MMR vaccine will still get sick if they’re exposed to the virus. (Again, immunity isn’t a perfect science!) Fully vaccinated people who become infected usually have a milder case, and are much less likely to spread measles to others.
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