Yes, but it is rare and usually mild

You can get measles even if you have been vaccinated, though the risk is very low. The measles vaccine is about 97 percent effective after two doses, meaning roughly 3 in 100 vaccinated people could still catch the virus if exposed. When vaccinated people do get measles, the illness is typically much milder than in unvaccinated people — fewer complications, shorter duration, and lower fever.

This happens because no vaccine is 100 percent effective. The measles vaccine works by training your immune system to recognize and fight the virus, but in a small number of people, that training does not stick or does not work as well as expected. Age at vaccination, the specific vaccine strain used, and individual immune system differences all play a role in whether protection develops fully.

Key Takeaways

  • Two doses of measles vaccine prevent infection in about 97 out of 100 people, so breakthrough cases happen but are uncommon.
  • Vaccinated people who do catch measles usually have milder symptoms, fewer complications, and recover faster than unvaccinated people.
  • A small number of people do not develop immunity after vaccination, even with two doses — this is called vaccine failure.
  • Measles spreads so easily that even high vaccination rates in a community do not eliminate all risk of exposure for vaccinated individuals.

How vaccine failure happens

Vaccine failure comes in two forms: primary and secondary. Primary failure means your immune system never built protection in the first place, even though you received both doses correctly. This happens in roughly 2 to 3 percent of vaccinated people and is often due to factors you cannot control — age at vaccination, certain medications, or how your individual immune system responds.

Secondary failure means you developed immunity after vaccination, but protection faded over time. This is less common with measles than with some other vaccines, but it can occur decades after your last dose. If you were vaccinated as a child and have not had a booster or natural infection since, your immunity may have weakened enough that you could catch measles if heavily exposed.

People most likely to experience primary failure include those vaccinated before age 12 months (when maternal antibodies can interfere), those with certain immune system disorders, and people taking medications that suppress immunity. If you fall into one of these categories and are unsure whether you developed protection, a blood test can measure your antibody levels.

What breakthrough measles looks like

When a vaccinated person catches measles, the illness follows a different pattern than in unvaccinated people. Fever is usually lower, the characteristic rash may be less dense or appear in a different order, and symptoms tend to resolve faster — often within a few days rather than a week or more.

Complications are much rarer in vaccinated people. Unvaccinated measles can lead to pneumonia, encephalitis (brain inflammation), and ear infections in a significant portion of cases. In vaccinated people who get measles, serious complications are uncommon. This is why public health officials distinguish between breakthrough cases and primary infection: the same virus causes very different outcomes depending on vaccination status.

Vaccinated people with measles are still contagious, though usually for a shorter window than unvaccinated people. This is why measles outbreaks can still occur in highly vaccinated communities if the virus is introduced — it spreads to the small percentage of people whose vaccines did not work, and they can pass it to others.

Why measles spreads despite high vaccination rates

Measles is one of the most contagious viruses known. One infected person will spread it to 12 to 18 unvaccinated people in the same space. Even in a community where 95 percent of people are vaccinated, that leaves 5 percent who are not protected — either because they were not vaccinated or because their vaccine did not work. The virus only needs to find those people to establish an outbreak.

This is why measles elimination depends on vaccination rates staying very high across entire regions, not just in individual communities. If vaccination rates drop below about 95 percent, measles can spread even among vaccinated people, because the virus circulates more widely and has more chances to find the small percentage of vaccinated people whose immunity failed.

Who should get a booster or immunity check

Most people vaccinated as children do not need a booster. Two doses of measles vaccine given at least 28 days apart provide long-lasting immunity in the vast majority of people. However, certain groups may benefit from checking their immunity status or getting an additional dose.

Healthcare workers, people planning to travel to countries where measles is common, and people born in 1957 or earlier (before routine vaccination) should know their immunity status. A simple blood test, called a titer, measures whether you have protective antibodies. If the test shows no immunity, a single additional dose of vaccine can restore protection. People with certain immune system conditions should discuss measles immunity with their doctor before any travel or high-risk exposure.

What to do if you think you have been exposed

If you know you have been exposed to measles and are unsure of your vaccination status, contact your doctor or local health department right away. Timing matters: the measles vaccine can prevent infection if given within 72 hours of exposure, even in people who were not previously vaccinated. If you were already vaccinated and have been exposed, your doctor may want to monitor you for symptoms, though the risk of serious illness is very low.

Measles symptoms typically appear 10 to 14 days after exposure. Early signs include fever, cough, runny nose, and red eyes — symptoms that look like a cold. The characteristic rash appears 3 to 7 days later, usually starting on the face and spreading downward. If you develop these symptoms after a known exposure, contact your healthcare provider before going to an office or clinic, so they can take precautions to prevent spread to others.

Frequently Asked Questions

If I was vaccinated as a child, do I still have immunity now?

Most people who received two doses of measles vaccine as children maintain immunity for life. Studies show protection remains strong decades later in the vast majority of vaccinated people. If you are unsure, a blood test can measure your antibody levels and tell you whether you are protected.

Can I get measles twice?

Natural measles infection provides lifelong immunity in almost all cases. If you have had measles once, you are protected for life. Vaccinated people who have a breakthrough infection also develop natural immunity on top of their vaccine-induced immunity, making reinfection extremely unlikely.

What is the difference between one dose and two doses of measles vaccine?

One dose prevents measles in about 93 percent of people. Two doses increase protection to about 97 percent. The second dose catches most of the people whose immune systems did not respond to the first dose, which is why two doses are recommended for complete protection.

If I am vaccinated and someone in my house has measles, will I definitely get it?

No. Even though measles spreads easily, vaccination significantly reduces your risk. If you are vaccinated and exposed to measles at home, you have roughly a 3 percent chance of infection — much lower than an unvaccinated person's risk, which is 90 percent or higher with close household exposure.

Should I get revaccinated if I cannot find my vaccination records?

If you cannot find records but remember receiving two doses as a child, you are almost certainly protected and do not need revaccination. If you have no memory of vaccination or only received one dose, getting revaccinated is safe and will ensure you have full protection. Your doctor can order a blood test first if you want to know your current immunity status before deciding.