Measles risk factors: am I at risk?

What measles is and how it spreads

Measles is an infectious disease caused by a virus. It causes a blotchy red rash that often starts on the head and moves down the body (MedlinePlus). Symptoms appear 7 to 14 days after contact with the virus: high fever (it may spike above 104 F), cough, runny nose, red and watery eyes, then the rash (CDC).

Measles spreads through the air when an infected person coughs or sneezes. You can catch it just by being in a room where a person with measles has been, up to 2 hours after that person has left (CDC). If one person has it, up to 9 out of 10 people in close contact who are not protected will become infected (CDC). People can spread measles from 4 days before through 4 days after the rash appears (CDC).

Who is at risk of catching measles

CDC puts it simply: anyone who is not protected against measles is at risk (CDC). In practice that means:

• People who have not had the MMR vaccine and have not had measles (CDC).
• Babies too young for their first routine dose, which is given at 12 to 15 months (CDC). CDC does not recommend measles vaccine for infants younger than 6 months (CDC).
• Travelers. Measles is still common in many parts of the world, and every year unvaccinated travelers catch it abroad and bring it back to the US (CDC).
• People in or near an outbreak. CDC notes that US measles cases have been increasing since early 2025, with several large outbreaks of more than 50 cases (CDC). Your local health department will tell you if you are at increased risk because of an outbreak (CDC).

Who is more likely to get very sick

Measles can cause serious problems at any age, but CDC lists these groups as being at higher risk of severe complications (CDC):

• Children younger than 5
• Adults older than 20
• Pregnant women. Without the MMR vaccine, measles in pregnancy may cause an early birth or a low-birth-weight baby (CDC).
• People with a weakened immune system, such as from leukemia or HIV infection

How serious it can be, in CDC's numbers (CDC):

• About 1 in 5 unvaccinated people in the US who get measles is hospitalized.
• As many as 1 in 20 children with measles gets pneumonia, the most common cause of death from measles in young children.
• About 1 child in every 1,000 who gets measles develops encephalitis (swelling of the brain).
• Nearly 1 to 3 in every 1,000 children infected with measles will die from breathing and brain complications.

I was vaccinated as a child. Am I protected?

Most likely, yes. CDC says most people vaccinated with MMR will be protected for life (CDC). How well the doses work, as CDC prints it: one dose of MMR is 93% effective against measles, and two doses are 97% effective (CDC).

For adults, CDC says (CDC): "One dose of MMR vaccine, or other presumptive evidence of immunity, is sufficient for most adults." It adds: "There is no recommendation for a catch-up program among adults for a second dose of MMR (e.g., people born before 1989 or otherwise)."

CDC counts any one of these as acceptable evidence that you are immune (CDC):

• Written records of adequate vaccination
• A lab test showing immunity
• A lab test that confirmed you had measles
• Birth before 1957. Most people born before 1957 likely had measles as children and are presumed protected.

Two cases where an adult should get vaccinated again:

• Vaccinated in the 1960s. If your records show the live measles vaccine, you do not need another dose. If you were vaccinated before 1968 with the killed (inactivated) vaccine, or you do not know which type you got, CDC says you should get at least 1 dose of live measles vaccine. The killed vaccine was used in 1963 to 1967 and did not work (CDC).
• No records. If you cannot find written records or other evidence of immunity, CDC says to get vaccinated, especially before international travel. There is no harm in an extra dose if you are already immune (CDC).

Some adults are advised to have 2 doses if they do not have other evidence of immunity: college and other post-high school students, healthcare workers, international travelers, close contacts of people with a weakened immune system, adults living with HIV who are not severely immunocompromised, and groups at increased risk during an outbreak (CDC).

Even vaccinated people can sometimes get measles if exposed, but their illness is generally milder and they are less likely to spread it (CDC).

Who CDC advises to get the MMR vaccine

• Children: 2 doses, the first at 12 to 15 months and the second at 4 to 6 years (CDC).
• Adults: at least 1 documented dose, unless they have other evidence of immunity (CDC).
• International travelers: be fully vaccinated before you go. Infants 6 to 11 months old should get 1 dose before travel, then 2 more doses after their first birthday (CDC). For the best protection, get vaccinated at least 2 weeks before you leave; if your trip is sooner, CDC says to still get a dose (CDC).

Some people should not get MMR or should wait, including people who are or may be pregnant, people with a weakened immune system from a disease or medical treatment and people who had a serious allergic reaction to a previous dose. Ask your doctor or pharmacist (CDC).

If you are not immune and were exposed, MMR given within 72 hours of the first exposure may give some protection or a milder illness (CDC). Recommendations can change. Your doctor, pharmacist or your child's doctor can tell you what fits you now.

Common questions

Can adults get measles?

Yes. Anyone who is not protected can catch it, and adults older than 20 are one of the groups at higher risk of severe complications (CDC).

Do I need a measles booster as an adult?

Usually not. One dose of MMR, or other evidence of immunity, is enough for most adults, and there is no catch-up recommendation for a second dose (CDC). The exceptions are the higher-risk groups above, people vaccinated with the 1960s killed vaccine, and anyone without records or other evidence of immunity (CDC).

Is measles the same as German measles?

No. German measles is rubella, a completely different illness (MedlinePlus). The MMR vaccine protects against both.

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