A guide to the MMR vaccine

This article is up to date as of March 30, 2026, and based on vaccine guidance provided by the U.S. Centers for Disease Control and Prevention (CDC). Individual states may adopt their own vaccine policies and recommendations based on local public health assessments and regulatory frameworks. For the most up-to-date information, consult your state or local health department or your health care provider.

Measles is a highly contagious disease caused by a virus, spreading easily when someone who is infected coughs, breathes, or sneezes and lingering in the air and on surfaces for up to two hours.

If one person has measles, they can infect nine out of ten people nearby if they are not protected. The MMR (measles, mumps and rubella) vaccine is widely considered to be the best way to help protect against measles. But who needs the MMR vaccine? When should children get their first dose? What if someone travels to a place with an active outbreak? And do people need a booster?

This guide provides key information about the MMR vaccine, including how it works, who may need it, when to get it and what is recommended to help stay protected.

In this article:

What is the MMR vaccine?

The MMR vaccine is a vaccine that can help protect children, teens and adults from measles, mumps and rubella, three highly contagious viral infections.

How the MMR vaccine works

The MMR vaccine is a live vaccine, which means it has a small amount of the weakened forms of the measles, mumps and rubella viruses in it. When someone gets the vaccine, the weakened viruses trigger an immune response without actually causing an infection. White blood cells recognize the viruses and produce antibodies to fight them. This helps build long-term protection, so if someone is ever exposed in the future, their immune system will know how to fight off the viruses.

What the MMR vaccine helps protect against

• Measles can cause cough, high fever, rash and red eyes. It can lead to serious complications, such as encephalitis, pneumonia or even death.
• Mumps can lead to fatigue, fever, jaw pain and swollen cheeks. In some cases, it can cause hearing loss and inflammation of the brain as well as reproductive problems in men.
• Rubella (German measles) is usually mild with a red rash and low-grade fever. But it can be extremely dangerous during pregnancy because it can cause miscarriage or birth defects.

How measles, mumps and rubella spread

• Measles spreads through the air when an infected person coughs or sneezes or when a person touches an infected surface and then touches their face.
• Mumps spreads through saliva (like when people share drinks or kiss) or through respiratory droplets when people cough or sneeze.
• Rubella spreads through coughing and sneezing.

Who needs the MMR vaccine?

The MMR vaccine is recommended for children, teens and adults who are not already immune.

Children

• First dose at 12 to 15 months old
• Second dose at 4 to 6 years old

The doses must be spaced apart by at least 28 days. As for children ages 7 or older, if they haven’t had both doses of the MMR vaccine at the recommended ages, they should still get vaccinated.

Teens and adults

• Teens and adults who didn't get both doses of the MMR vaccine as kids might need one or two doses to achieve maximum protection.
• People born before 1957 are usually considered immune to measles and mumps. Back then, these diseases were more common, so most people got exposed and developed natural immunity before vaccines were available.
• People who were vaccinated for measles between 1963 and 1967 may have received an older version that wasn’t fully effective. They should check with a health care provider to see if getting a modern vaccine is recommended.

Groups at a higher risk of exposure

• College students. Campuses have close living quarters and frequent social interactions, increasing the risk of outbreaks of infectious diseases. Plus, many colleges require proof of immunization. Those unsure of their immunity should get two doses at least 28 days apart.
• International travelers. Anyone traveling internationally should be fully vaccinated with the MMR vaccine before departure if they are not already protected. Ideally, vaccination should be completed at least two weeks before travel, but those leaving sooner should still get a dose. Infants ages 6 to 11 months should receive one dose before international travel, followed by two additional doses after their first birthday to complete the series.
• Health care providers. Health care providers born in 1957 or later with no evidence of immunity to measles, mumps, or rubella, may consider completing a two-dose series for protection against measles or mumps and at least one dose for protection against rubella. For those health care personnel born before 1957 with no evidence of immunity for measles, mumps, or rubella, they should consider following the same dosing guidance as those born in 1957 or later.

Who can’t get the MMR vaccine?

Some people are advised not to get the MMR vaccine or to wait. People should check with their health care provider whether they should get the vaccine or wait if they fall in the following groups:

• People who are pregnant. The MMR vaccine is a live, weakened virus vaccine. Because of this, people of childbearing age should avoid becoming pregnant for at least a month after vaccination. Anyone who is already pregnant should not receive the MMR vaccine. If someone is pregnant and not vaccinated, they should wait to get the MMR vaccine until after giving birth.
• Weakened immune systems. For people with serious immune system problems, the MMR vaccine can cause an infection that may be life-threatening. Because of this risk, anyone with a severely weakened immune system shouldn’t receive the MMR vaccine.
• Severe allergies to the vaccine. In very rare cases, a person may have a serious allergic reaction to the MMR vaccine. Anyone who has had a life‑threatening allergic reaction to neomycin or any other ingredient in the MMR vaccine should not receive it.
• Feeling sick. People with mild illnesses, like a cold, can still get the MMR vaccine. However, those who are moderately or severely ill should usually wait until they’re feeling better before getting vaccinated.
• Blood transfusion or treatments. People who have recently had a blood transfusion or received other blood products should not get the MMR vaccine right away. In these cases, a health care provider may recommend waiting three months or longer before getting vaccinated.

If someone is unsure if they should get an MMR vaccine now or later, contact a health care provider.

Vaccine side effects

Vaccines, like any medicine, can have side effects. However, they’re usually mild and go away on their own.

Possible side effects:

• Fever
• Mild rash
• Sore arm where the vaccine was given
• Temporary joint pain and stiffness

Uncommon side effects include:

• Swelling in the cheeks or neck

Rare but serious side effects:

• Fever-induced seizure
• Signs of a severe allergic reaction (e.g., hives, swelling of the face and throat, trouble breathing, a fast heartbeat, dizziness, or weakness)

Anyone experiencing a serious reaction should seek medical attention immediately. For mild side effects, consult a health care provider.

How safe and effective is the vaccine?

The MMR vaccine is very safe and effective at preventing measles, mumps, and rubella. For most people, it provides long-lasting protection, although immunity to mumps can decrease over time in some cases.

This means a small number of vaccinated people may no longer be protected later in life. While some vaccinated individuals can still get measles, mumps or rubella if they’re exposed, their symptoms are usually milder, and they’re less likely to spread the illness to others.

The latest data shows how well the vaccine works:

One dose:

• 93 percent effective against measles
• 72 percent effective against mumps
• 97 percent effective against rubella

Two doses:

• 97 percent effective against measles
• 86 percent effective against mumps

Key takeaways

The MMR vaccine is a safe and effective way to protect against measles, mumps and rubella, which are highly contagious viral diseases. It’s recommended for children, teens and adults who aren’t already immune, with specific guidance for at-risk groups. Most people who receive the recommended doses are protected for life, although some may need additional guidance based on age, health status or exposure risk. Anyone who is unsure about their vaccination status or eligibility should talk with a health care provider.