Yes, you can get measles after vaccination, but it is rare
The measles vaccine is highly effective, but it does not protect everyone who receives it. About 97 out of 100 people who get two doses of the MMR vaccine (measles, mumps, rubella) develop immunity to measles. That means roughly 3 out of 100 vaccinated people remain unprotected or lose protection over time. If an unprotected vaccinated person is exposed to measles, they can catch it.
When vaccinated people do get measles, the illness is usually milder than in unvaccinated people. They typically have fewer spots, lower fevers, and recover faster. Serious complications like pneumonia or brain inflammation are much less common in vaccinated people who break through with measles.
The vaccine's protection can also fade over decades. Most people who were vaccinated as children stay protected for life, but some studies suggest immunity may weaken after 30 or 40 years. This is rare enough that doctors do not routinely recommend booster shots for adults who were vaccinated in childhood.
Key Takeaways
- About 3 out of 100 people vaccinated with two MMR doses do not develop immunity or lose it over time.
- Measles in vaccinated people is usually milder, with fewer complications than in unvaccinated people.
- Certain medical conditions and medications can weaken vaccine protection, even in people who were vaccinated.
- If you are unsure whether you are protected, a blood test can show whether you have immunity to measles.
Why some vaccinated people do not develop immunity
Immunity after vaccination depends partly on how your immune system responds. Some people's bodies simply do not mount a strong enough response to the vaccine, even when it is given correctly. This is more common in people with certain genetic traits, though doctors cannot predict who will have a weak response before vaccination.
Age at vaccination matters too. Infants vaccinated before 12 months old are less likely to develop immunity than older children, because maternal antibodies can interfere with the vaccine. This is why the standard schedule gives the first MMR dose at 12 to 15 months, when maternal protection has faded.
Medical conditions and medications also affect how well the vaccine works. People with weakened immune systems—from HIV, cancer treatment, or immunosuppressive drugs—may not develop immunity even after vaccination. People taking certain steroids or biologic medications for autoimmune diseases fall into this group as well.
When vaccinated people catch measles
A vaccinated person who catches measles is called a vaccine breakthrough case. This happens most often during large measles outbreaks, when the virus spreads widely enough that it reaches unprotected vaccinated people. In areas where measles is rare, breakthrough cases are uncommon.
The symptoms in a breakthrough case are usually the same as in unvaccinated people—fever, cough, runny nose, and the characteristic measles rash—but they tend to be less severe. Vaccinated people are less likely to develop the high fevers (over 104°F) that unvaccinated people often experience. The rash may be lighter or appear in a different pattern.
Vaccinated people with measles are still contagious and can spread the virus to others. They shed the virus from about four days before the rash appears until four days after it appears. This is why people with measles are asked to stay home during this window, regardless of vaccination status.
How to know if you are protected
If you received two doses of MMR vaccine at least 28 days apart, you are very likely protected. The first dose is usually given at 12 to 15 months, and the second at 4 to 6 years old. If you received both doses on this schedule, your protection is considered complete.
If you are unsure of your vaccination history, a blood test can tell you whether you have immunity. The test looks for antibodies to measles in your blood. Some doctors order this test for people who work in healthcare, travel internationally, or have other reasons to know their status for certain.
If a blood test shows you do not have immunity, you can receive another MMR dose. Even people who did not respond to the first two doses sometimes develop immunity after a third dose, though this is not standard practice. Talk with your doctor about whether a booster makes sense for your situation.
Who should be most concerned about breakthrough measles
People with weakened immune systems face the highest risk of measles complications, whether vaccinated or not. This includes people with HIV, people undergoing chemotherapy, people who have had organ transplants, and people taking immunosuppressive medications for conditions like rheumatoid arthritis or inflammatory bowel disease.
Pregnant people who are not immune should also be cautious. Measles during pregnancy can cause miscarriage or premature birth. If you are pregnant and unsure of your immunity, a blood test can confirm your status. The MMR vaccine cannot be given during pregnancy because it contains a live virus, but it can be given right after delivery if needed.
Infants under 12 months old cannot receive the MMR vaccine yet and depend on immunity from vaccinated people around them. If you are in close contact with infants—as a parent, grandparent, or caregiver—your vaccination status matters for their protection.
What to do if you think you have measles
If you have fever, cough, and a rash that started on your face and spread downward, contact your doctor before going to the office or hospital. Tell them you think you might have measles so they can take precautions to prevent spreading it to other patients. Many doctors will ask you to wait in a separate area or conduct the visit by phone or video.
Your doctor can diagnose measles by examining the rash and asking about your symptoms and vaccination history. A blood test or throat swab can confirm measles if needed. There is no specific treatment for measles itself—care focuses on managing fever and keeping you comfortable while your immune system clears the virus.
Most people recover from measles within one to two weeks. Serious complications like pneumonia, brain inflammation, or secondary infections are less common in vaccinated people but can still occur. If you develop severe symptoms like difficulty breathing, confusion, or very high fever, seek emergency care.
Frequently Asked Questions
If I had measles as a child, do I need the vaccine?
No. Having measles once gives you lifelong immunity. You do not need the vaccine if you have confirmed measles immunity from a past infection. A blood test can confirm this if you are unsure.
Can the MMR vaccine give you measles?
The MMR vaccine contains a weakened live virus, not the full measles virus. It cannot cause measles. Very rarely, vaccinated people develop a mild rash a week or two after vaccination, but this is not measles and is not contagious.
How long does measles immunity last after vaccination?
For most people, immunity lasts a lifetime after two doses of MMR vaccine. Some studies suggest immunity may weaken slightly after 30 to 40 years, but this is uncommon and does not usually require a booster shot.
Should I get revaccinated if I am traveling to a country with measles?
If you received two MMR doses as a child, you are protected and do not need another dose before travel. If you are unsure of your vaccination history or received only one dose, talk with your doctor about whether a booster or a blood test makes sense before you travel.
Can you get measles twice?
Getting measles once gives you lifelong immunity, so catching it twice is extremely rare. If someone is diagnosed with measles twice, the first diagnosis was usually incorrect or the person had a very weak immune system that prevented normal immunity from developing.