Why some adults may need another dose of measles vaccine

As measles cases are showing up more often this year, officials caution the U.S. might no longer be able to say the disease is eradicated.

A rising number of measles cases in the U.S. this year is raising concerns over a comeback of a disease that was declared eliminated in this country 24 years ago.

A measles report from the Centers for Disease Control and Prevention last week concluded that the spike in cases means more public health efforts are needed to increase routine vaccination coverage.

This year there have been 121 infections reported in 17 states, according to the Centers for Disease Control and Prevention. That is well above the total of 58 cases documented for the country for all of 2023.

Among the national cases this year were three in Georgia, all of them in unvaccinated people. The latest was confirmed Thursday in a person traveling with an international group of students. Earlier this year, state health officials confirmed two cases of measles in a metro Atlanta family after one of the family members had traveled internationally.

Before this year, the last measles cases in Georgia were reported in 2020.

While the numbers might seem low, measles is a serious illness that can lead to severe complications.

The airborne virus is also highly contagious. If one person has it, up to 90% of the people close to that person who are not immune will also become infected, according to the CDC.

Falling vaccination rates and a rise in cases globally are raising questions for older adults who got a measles vaccine a long time ago, or maybe they aren’t sure if they ever got vaccinated as a child.

Here’s what you need to know about the measles vaccine and what to do if you are unsure about your vaccination status.

Measles, which produces a skin rash, is an airborne virus that is highly contagious. If one person has it, up to 90% of the people close to that person who are not immune will also become infected, according to the CDC. (File)

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People born before 1957 are nearly always immune. The measles vaccine was made available in 1963, but in the decade before that virtually every child got measles by 15, making them immune. The CDC considers people born before 1957 to be protected from measles.

But for those born later, it may not be so simple. Measles vaccines first became available in 1963. Laws requiring a measles vaccine before attending school rolled out slowly and over the years so not all children were automatically vaccinated. Initially, there were two vaccines: a live attenuated version (which is a live form of the virus weakened in medical labs), or a “killed” vaccine (which contains the dead virus), which was not considered effective and is no longer used.

So some people who received the vaccine between 1963 and 1967 may have gotten a dose of the killed vaccine and they should consider getting an updated vaccine, according to Dr. Jayne Morgan, executive director of health and community education for Piedmont Healthcare.

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.