Amid one of the largest measles outbreaks in the U.S. in recent history, vaccines are on the minds of many Americans.

The Centers for Disease Control and Prevention reported this week that the number of measles cases this year has climbed to 839 in 23 states, affecting mostly unvaccinated people. Most people in the U.S. are vaccinated against measles when they’re children as part of the routine immunizations they get in primary care.

We’re used to kids needing lots of shots to ward off lots of illnesses, but what about adults? The CDC recommends that adults get multiple vaccines for conditions ranging from tetanus to influenza to cervical cancer. The shots can be a bit trickier to keep track of, as many adults go to the doctor less frequently than kids do, but those vaccinations are equally important for staying healthy.

“Many adults are not aware of what vaccines they actually need,” says Dr. Pamela Rockwell, an associate professor of family medicine at the University of Michigan who works with the CDC’s Advisory Committee on Immunization Practices. “That is also balanced by physician unawareness of what vaccines they should be recommending. It’s gotten very complicated, and it is difficult to keep up with all the changes.”

So we’re here to answer some common questions about adult vaccines.

I was vaccinated against measles as a child, but the measles outbreak makes me worry that I’m no longer immune. Do I need to be revaccinated as an adult?

If you received the standard two doses of the modern measles, mumps and rubella (MMR) vaccine, you’re all set. You shouldn’t need to be revaccinated, because you’re considered immune for life.

And if you were born before 1957, doctors assume you were exposed to measles as a child and are already immune.

However, a version of the vaccine produced in the mid-to-late 1960s wasn’t as effective as the current regimen, so if you were vaccinated before 1968, you should talk to your doctor about whether you need another shot. If you were born after 1957 but for some reason never got immunized, you should also get the MMR vaccine.

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