Why some adults may need another dose of measles vaccine

The CDC said for those born after 1957, one dose of live vaccine is considered adequate unless a person is at high risk of exposure. Those at higher risk — such as those working in health care, who are attending college, or who travel internationally — should consider having two doses.

If you got the standard two doses of the measles vaccine after 1967, you should be protected against measles for life.

—What if I don’t know if I’m immune?

For those unsure if they’ve either had measles or took the vaccine as a child, the CDC said there’s no harm in taking another, now known as the measles, mumps and rubella (MMR) vaccine. While healthcare providers can do a blood test to determine immunity, that step is generally not recommended.

Jodie Guest, professor and vice chair of the department of epidemiology at Emory University’s Rollins School of Public Health, also says if you are not sure of your immunity, go ahead and get vaccinated. “Go ahead and get the vaccine and do not worry about getting tested,” Guest said.

—Should younger adults also consider a measles vaccine?

Measles is a dangerous virus, so anyone of any age unsure of their vaccination status should get one. Guest said more than half of the people sickened with measles this year in the U.S. have required hospitalization, and close to a third of them were adults at least 20 years of age.

“We have likely forgotten how dangerous measles is as vaccination rates have been high and kept us safe,” said Guest. “With vaccination rates falling, we are seeing a rise in a vaccine preventable illness that causes death and long-term, severe complications.”

Severe complications from measles include pneumonia and encephalitis (swelling of the brain). Nearly one to three of every 1,000 children who become infected with measles will die from respiratory and neurologic complications, according to the CDC.

—How effective is the MMR vaccine?

The measles vaccine is very effective, according to the CDC. Two doses of an MMR vaccine are about 97% effective at preventing measles if exposed to the virus. One dose is about 93% effective.

Very few people — about three out of 100 — who get two doses of measles vaccine will still get measles if exposed to the virus, according to the CDC.

Experts aren’t sure why. It could be that their immune systems didn’t respond as well as they should have to the vaccine. But the good news is, fully vaccinated people who get measles seem more likely to have a milder illness.

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