Can You Get Measles if You Were Vaccinated?
A guide to the measles outbreak for people who think they were vaccinated—or aren't really sure.
Image: Don Johnston/Flickr
Before the measles vaccine was licensed in 1963, “virtually all children” got the measles, with estimates of 3.5 million cases per year and hundreds of deaths, according to the Centers for Disease Control and Prevention (CDC). After widespread vaccination efforts, those numbers fell: there were 1,697 reported cases in 1982, and only 86 reported cases in 2000, when measles was declared “eliminated.”
But eliminated doesn’t mean gone forever. Due to pockets of unvaccinated people and international travelers bringing measles home from abroad, measles is back. Just this year, there have been more than 700 cases of measles in 22 states.
Most of us born after 1963 haven’t lived in an era where we needed to excessively worry about measles, but with the rise in outbreaks, you may have some questions: Did I get my vaccine? How can I tell? Am I safe, or do I need another dose? Tom Clark, the deputy director of CDC's Division of Viral Diseases, and Allison Bartlett, an associate professor of pediatric infectious diseases at the University of Chicago, answered some vital questions.
Am I at risk?
Measles is a highly contagious virus, and before immunizations, 75 percent of people exposed to it for the first time would get infected. That means that unvaccinated people are the most at-risk, and anyone who is under the age of five or over the age of 20 and also unvaccinated is at higher risk for measles complications, said Clark. Your risk lowers dramatically if you’ve received the vaccine– even if you’re nearby one of the outbreaks.
How do I know if I’ve gotten the measles vaccine?
The CDC recommends that everyone be vaccinated against measles, and that children get two doses – the first at 12 to 15 months old, and a second dose at four to six years old.
Most state’s public kindergartens require vaccinations, including the measles vaccine. If you attended a public school, unless your parents asked for an exemption, it’s likely you did receive at least one dose of the MMR vaccine. To know for sure, you will have to find the written documentation that proves it.
You may have to do a little detective work. First stop: call your parents. “Some people are lucky to have a super-obsessive mother like I do and has made copies in the baby book,” Bartlett said. If your parents don’t have your records, many states have immunization registries—but some haven’t been around for very long. That means adults may not find their records there.
You can then try to contact your pediatrician, or family doctor, who could have your records still on file. Many universities also require proof of vaccination, and you can try to request a copy from them as well—they’re more likely to have your documents than your kindergarten.
Finally, if you still can’t track down your records, you can check your immunity with a blood test, which will measure your antibody response to the measles virus.
Should I get another dose of the vaccine?
Some people might benefit from getting another measles vaccine shot. If you were vaccinated between 1963 and 1967, you received a version of the vaccine that contained an inactive virus, which is not as effective as the vaccine that’s used today.
Those people could opt to check their immunity through a blood test, but “in a situation like this with measles circulating, we don't necessarily want to wait and find that answer to that test,” Bartlett said— the turnaround time for results can vary depending on if your doctor has to send samples to another lab, or if there’s a wait to get samples processed. It may be best to go ahead and get another shot.
If you’re over 30, you could also consider getting another dose. Getting two doses of the vaccine wasn’t implemented until 1989– if you were born before that, it’s possible you only got one shot, rather than two.
Other higher-risk groups like “college and other students, healthcare personnel, and international travelers,” might want to seek out a booster shot as well, Clark said. Many measles cases result from international travelers without immunity bringing home infections. The CDC lists travel notices for countries that are currently at risk for measles, which currently includes Israel, Ukraine, Japan, Brazil and the Philippines. If you’re traveling to those countries, and can’t verify your immunity status, consider getting another shot. You can look up all the vaccine requirements for travel to any country at the CDC’s Traveler’s Health site.
If you’re unsure and decide to get one just in case, there’s no harm in it, Bartlett said. There isn’t any risk to getting a second dose.
During these outbreaks, should parents give their children the vaccine earlier than 12 months?
Immunization can be recommended as early as six months, but usually only for kids who are traveling internationally to areas where there may be measles.
In certain neighborhoods in New York City, like Borough Park and Crown Heights, the NYC Department of Health and Mental Hygiene has recommended earlier doses of MMR vaccine to children 6 to 11 months during the current outbreak. In Williamsburg, this extra dose is required under the Public Health Emergency declaration. "This dose would not count toward the routine, two-dose vaccine series," the NYC Health website said.
The earlier dose doesn't count towards the usual two-dose vaccination requirement because at that early of an age, the measles vaccine might not be completely effective. “The reason that we usually wait to give the measles vaccine until kids are one year old, is that passive immunity, or the antibodies that get transferred to the baby from mom, can interfere with how the vaccine works,” Bartlett said.
Clark said that depending on the nature of the outbreaks, how they evolve and what age groups they affect, recommendations could shift—so keep an eye on your local health department's websites. What’s still most important for babies right now is herd immunity: the immunity status of the adults surrounding them.
Are the current outbreaks affecting herd immunity?
Herd immunity is important for vulnerable people who can’t get the vaccine for a medical reason, or because they’re too young. Two doses of the MMR vaccine are about 97 percent effective at preventing measles, which is enough to prevent spread in a community—given that 98 percent of people in that community are vaccinated. Herd immunity starts to break down when the number of vaccinated people drops, and that’s a big factor in what’s causing the rising infections we’re seeing now.
Let’s say you were born in 1985, can’t find your vaccination records even though you went to public schools, and are going to be around people or babies who can’t be or haven’t been vaccinated. It could be worth checking your immunity with a blood test, or getting a second shot. If you are going to be traveling to a country with measles, and are unsure of your immunity status, getting a second shot before your trip could also help ensure the safety of your community.
“During measles outbreaks, efforts should be made to ensure that everyone at risk for exposure and infection is protected against measles through vaccination or past infection,” Clark said.
But not to fear: herd immunity isn’t broken. To restore it, the current infections need to be addressed, and we need to get those vaccination levels back up. This isn’t a case where we don’t have a solution to a problem: Bartlett said that the measles vaccine is one of the most effective we have.
“The number of measles cases we're seeing is alarming and much higher than we've seen in a long time, but there is also an incredibly large number of people who are not getting measles right now because of their immunity in having received the vaccine,” Bartlett said. “It's important to be aware of measles and do what we can to keep everybody safe, but it also is a reminder of the power of vaccination when universally applied.”
*This post has been updated to include NYC's vaccination recommendations.
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