Why Many Adults Should Get Their Measles Shot — Again

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Anyone born before 1978, but especially those born prior to 1958, may want to get a vaccination. (Photo: Corbis)

Since unvaccinated children spreading measles seem to constitute most of the buzz on the recent outbreak of the virus, there’s a fact that’s getting lost in the shuffle: The majority of those infected are actually adults.

According to new numbers from California, of the 92 confirmed measles cases in the state, 62 percent are adults over age 20.

To us adults who think that, when it comes to measles, we’re totally homefree, those stats are scary. But there are several fascinating reasons for this — harking back to the mid-20th century when the measles vaccine was first released. 

Fact: If you were born before 1957, you’re probably not vaccinated.

When docs started administering measles vaccinations in 1963, they recommended that only those who were born after 1957 get shots. Before that date, measles was so common and so contagious, it was extremely likely you’d been exposed and were thus immune — CDC surveys suggest that 95 to 98 percent of those born before 1957 are immune to measles. However, that fact is not totally certain. Some adults today may not be immune if they didn’t get vaccinated.

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A child receives one of the first measles in 1963. (Photo: Corbis)

Fact: If you were inoculated between 1963 and 1967, you may have received an ineffective vaccine.

When the measles shots first came out, there were different types: the version containing “live” virus, which is still in use today, and the “killed” or inactivated measles vaccine, which was withdrawn in 1967 because it quickly lost its effectiveness over time. In fact, in a 1965 study, only one quarter of the children given three doses of the “killed” vaccine over a three-month period still had measles antibodies a year later. And even after a yearly booster injection, 43 percent of children exposed to measles developed it.

The CDC recommends that people who were vaccinated prior to 1968 with either inactivated (killed) measles vaccine or a measles vaccine of unknown type should be revaccinated with at least one dose of live attenuated measles vaccine.

Related: Measles Cases This Year Show Sign Of Disturbing Trend

The only way to know which vaccine you received is by looking at your medical records. If you don’t have specific documentation, consider getting a shot.

Fact: If you were born between 1963 and 1977, you may have gotten only one dose of the measles vaccination.

Large-scale measles vaccinations began in 1963, but it wasn’t until 1989 that the American Academy of Pediatrics began recommending that two doses of the live vaccine be given to children after their first birthday. That’s because if you get one dose, it’s 95 percent likely to be effective — but with two doses it’s 99 percent effective. In 1989 — and this still stands today — health officials determined that kids either be given this second “booster” shot between ages 11 and 12, or when they enter school between ages 4 and 6 years.

In 1989, 11 and 12 year olds were born in 1977 and 1978 — so anyone born from those years forward probably got a second dose of the vaccination as a kid. You may have also received a second shot if you’re a healthcare worker, travel internationally, or went to college. But given this data, people born before 1978 should check their medical records.

Fact: Measles immunity can lag over time.

Even if you are an adult who did get the shot, says Thomas Kelley, MD, a family practice physician and chief quality officer at South Seminole Hospital — Orlando Health, there’s a chance you’re still prone to contracting the virus. “Vaccines are generally not 100 percent effective,” he tells Yahoo Health. “Even if you are fully vaccinated as recommended, you may not be fully protected,” he says. “On top of that, the farther away you are from the time you got the shot, immunity can lag a bit.”

A Finnish study published in the Journal of Infectious Diseases showed that antibodies induced by the MMR (measles, mumps, rubella) vaccine waned after two doses of the shots were administered and researchers checked back in 20 years. The CDC has also noted that the effectiveness of shots like those for whooping cough and flu also dwindles as time passes. A study from the International Journal of Tuberculosis and Lung Disease also showed the BCG vaccine to protect against tuberculosis may also decrease in effectiveness over the years.

Related: California Measles Outbreak Shows How Quickly Disease Can Resurface in U.S.

The good news is that, if you got two doses of the vaccine after 1963, odds are you’re probably good to go — or at least partially immune, Kelley says. “The problem is, we’re not all walking around with full medical records to be certain,” he says. “Some people aren’t sure if they’ve been fully immunized.”

Fact: You can find out if you’re immune to measles

Kelley says it’s a simple blood test to determine if you’ve been vaccinated; doctors can measure the antibodies in your blood that will show if you’re immune. Ask your PCP for a “measles titer” to check your status.

Fact: There’s no harm in getting vaccinated again

That said, if anyone is unsure or worried about the virus, there’s another option. “There is no harm in getting vaccinated again,” Kelley says says. “For instance, if you’re going to be in an area where there’s been an outbreak or the potential is there, like a daycare center or you’re going to be traveling abroad, you may not want to wait a week for results of a blood test.”

Kelley is recommending that his patients get vaccinated again if they’re questioning how safe they are from measles. It’s better to know you’re protected than to wonder if you should have been. Get your measles status taken care of now. You’ll be safe and help reduce the spread of the virus.

Up Next: 4 Major Reasons Doctors Are So Scared of Measles