Yes, but it is rare and depends on which vaccine you received and how long ago

You can get measles after vaccination, though the risk is low. The measles vaccine is highly effective—two doses prevent measles in roughly 97 out of 100 people who receive them. But that means about 3 in 100 vaccinated people can still catch measles if exposed to the virus. A smaller group of vaccinated people may have had their immunity fade over decades, or their immune system may not have responded well to the vaccine in the first place.

The chance of getting measles after vaccination depends on several factors: whether you received one dose or two, how many years have passed since your last dose, and how strong your immune system is. People who received both doses of the MMR vaccine (measles, mumps, rubella) as children have the strongest protection. Those who received only one dose, or who were vaccinated many years ago, face a higher risk if exposed—though still much lower than unvaccinated people.

If you do get measles despite vaccination, the illness is usually milder than it would be in an unvaccinated person. You may have fewer spots, a lower fever, and a shorter illness. But you can still spread measles to others, including people who cannot be vaccinated.

Key Takeaways

  • Two doses of the MMR vaccine prevent measles in about 97 out of 100 people, meaning roughly 3 in 100 vaccinated people can still catch it if exposed.
  • People who received only one dose of the vaccine, or who were vaccinated decades ago, have a higher risk of infection than those with two recent doses.
  • Measles after vaccination tends to be milder—fewer spots, lower fever, shorter duration—but you can still transmit it to others.
  • Immunity can fade over time in some people, which is why a second dose is recommended and why some adults may need a booster in certain situations.

Why vaccination does not may provide lifelong protection

The measles vaccine works by training your immune system to recognize and fight the virus. But immunity is not always permanent. In a small number of vaccinated people, the immune response weakens over time, especially if they never encounter the actual virus to "remind" their immune system. This is called waning immunity.

The second dose of the MMR vaccine exists partly to catch people whose immune system did not respond well to the first dose. Some people's bodies simply do not mount a strong response to vaccination—this can happen for reasons including age at vaccination, genetics, or underlying immune conditions. A second dose gives those people another chance to develop protection.

Additionally, immunity can fade decades after vaccination. Someone vaccinated as a child in the 1980s may have lower protection now than they did at age 10. This is one reason health authorities sometimes recommend a booster dose for adults in certain situations, such as healthcare workers or people traveling to countries where measles is still common.

Who is most likely to get measles despite vaccination

People who received only one dose of the MMR vaccine face the highest risk among vaccinated groups. This includes some adults who were vaccinated before the two-dose schedule became standard in the 1980s. If you were born between 1957 and 1989 and received only one dose, your protection may be lower than someone who received two doses.

People with weakened immune systems—from HIV, certain medications, or cancer treatment—may not develop strong immunity even after vaccination. In some cases, they cannot receive the live MMR vaccine at all and must rely on other preventive measures.

Older adults who were vaccinated decades ago may have experienced some decline in immunity, though two-dose vaccination still provides substantial protection. Healthcare workers and people who travel internationally are sometimes offered a booster dose to strengthen their protection before exposure.

What happens if a vaccinated person gets measles

Measles in a vaccinated person—called breakthrough measles—is usually milder than in someone who was never vaccinated. A vaccinated person may have fewer of the characteristic red spots, a lower fever, and a shorter illness lasting only a few days instead of a week or more. Some vaccinated people have such mild symptoms that they do not realize they have measles.

However, mild does not mean harmless. Even vaccinated people can develop complications like pneumonia or encephalitis (brain inflammation), though these are less common than in unvaccinated people. And because symptoms may be subtle, a vaccinated person might not isolate themselves and could spread measles to vulnerable people around them—infants too young to be vaccinated, pregnant women, or people with immune conditions.

If you think you have measles—even if you were vaccinated—contact your doctor before visiting in person. A healthcare provider can test you and advise on isolation to prevent spreading the virus to others.

How to know if your vaccination is still protecting you

You cannot know your immunity level without a blood test. A test called a titer measures antibodies against measles and shows whether you have protection. However, routine titer testing is not recommended for most people who received two doses of the MMR vaccine as children, because the protection is assumed to be strong.

Titer testing may be offered to healthcare workers, people planning to travel to countries with measles outbreaks, or people with immune conditions. If your titer shows low or no antibodies, a booster dose of the MMR vaccine may be recommended.

If you are unsure whether you were vaccinated or how many doses you received, your doctor can check your vaccination record. If no record exists, you can receive the MMR vaccine again—getting an extra dose is safe and will not cause harm, even if you already have immunity.

Measles outbreaks and vaccinated people

During measles outbreaks, some vaccinated people do get infected, especially in clusters where many people are exposed to high levels of the virus. This does not mean the vaccine failed—it means the vaccine is not 100 percent effective, which was always known. In outbreaks, unvaccinated people make up the vast majority of cases and hospitalizations.

When vaccinated people do get measles during an outbreak, they typically recover faster and have fewer complications than unvaccinated people. But they can still spread the virus, which is why public health authorities track breakthrough cases and recommend that exposed vaccinated people monitor themselves for symptoms.

What to do if you are vaccinated and exposed to measles

If you know you were exposed to measles and you are vaccinated, your risk of infection is low but not zero. Watch for symptoms starting 7 to 21 days after exposure: fever, cough, runny nose, red eyes, and then the characteristic red spots inside the mouth followed by a rash on the face and body.

If symptoms develop, stay home and contact your doctor by phone before visiting in person. This prevents spreading measles to others in the waiting room. A healthcare provider can test you and advise on how long to isolate.

If you are unvaccinated or unsure of your vaccination status and you have been exposed, contact your doctor immediately. In some cases, a dose of the MMR vaccine given within 72 hours of exposure can prevent measles or reduce its severity.

Frequently Asked Questions

If I was vaccinated as a child, do I need a booster now?

Most people who received two doses of the MMR vaccine as children do not need a booster. However, healthcare workers, people traveling to countries with measles, and people with certain immune conditions may be offered a booster dose. Ask your doctor whether a booster is recommended for your situation.

Can I get measles twice?

Getting measles once gives you lifelong immunity—you cannot get it again. However, you can get measles once even if vaccinated, because vaccination is not 100 percent effective. After that infection, you have permanent immunity.

Does breakthrough measles mean the vaccine does not work?

No. Breakthrough cases are expected because no vaccine is 100 percent effective. The measles vaccine prevents infection in 97 out of 100 people, which is why measles is rare in vaccinated populations. When cases do occur in vaccinated people, they are usually milder and less likely to cause serious complications.

Should I get a titer test to check my immunity?

Routine titer testing is not recommended for people who received two doses of the MMR vaccine as children. If you are unsure whether you were vaccinated or received only one dose, ask your doctor. Titer testing may be useful for healthcare workers or people with immune conditions.

What if I cannot remember whether I was vaccinated?

Check with your parents, your childhood doctor's office, or your school records. If you cannot find documentation and you were born after 1956, it is safe to receive the MMR vaccine again. An extra dose will not cause harm and will ensure you have protection.