MMR Vaccine: Schedule, Effectiveness, Side Effects, and Who Should Avoid It
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
The MMR vaccine combines three vaccines in one shot to protect against measles, mumps and rubella, three potentially serious viral illnesses that can cause complications such as pneumonia, brain inflammation, blindness, hearing loss and death. Healthcare providers recommend two doses, and children usually get one between 12 and 15 months of age and another between 4 and 6 years [1].
Quick Answer: What is the MMR vaccine?
The MMR vaccine is a live, weakened vaccine that trains the immune system to fight measles, mumps and rubella. Two doses are 97% effective against measles and rubella and 86% effective against mumps. Side effects are usually mild, such as soreness or fever. It should not be given to people who are pregnant, immunocompromised or severely allergic. [1]
What the research says
Two doses were highly effective against measles and mumps in a large Cochrane review. The review pooled 138 studies with 23,480,668 participants. Effectiveness against measles was 95% after one dose (relative risk 0.05; 95% CI 0.02 to 0.13) and 96% after two doses (RR 0.04; 95% CI 0.01 to 0.28), both with moderate certainty. For mumps with Jeryl Lynn-containing vaccines, effectiveness was 72% after one dose and 86% after two doses. The authors concluded that the evidence supports use of MMR for mass immunization and noted that more evidence is needed on whether protection wanes over time (Di Pietrantonj et al., Cochrane Database Syst Rev, 2021 [2]).
Serious side effects were rare, and the same review found no link with encephalitis or autism. The attributable risk of vaccine-induced febrile seizures was estimated at 1 per 1,700 to 1 per 1,150 doses, and the risk of immune thrombocytopenic purpura (ITP) at about 1 case per 40,000 doses, which is smaller than the risk after natural infection. There was no evidence of an association with encephalitis or encephalopathy (rate ratio 0.90; 95% CI 0.50 to 1.61) or autism spectrum disorders (rate ratio 0.93; 95% CI 0.85 to 1.01; 1,194,764 children) (Di Pietrantonj et al., Cochrane Database Syst Rev, 2021 [2]).
A nationwide Danish cohort found no increased autism risk. Among 657,461 children followed for 5,025,754 person-years, 6,517 were diagnosed with autism. Comparing MMR-vaccinated with unvaccinated children, the fully adjusted hazard ratio for autism was 0.93 (95% CI 0.85 to 1.02), and no increased risk appeared in subgroups such as children with a sibling history of autism (Hviid et al., Ann Intern Med, 2019 [3]).
What Is the MMR Vaccine?
The MMR vaccine combines three vaccines into a single shot that protects against measles, mumps and rubella. These are serious viral infections that can cause complications such as pneumonia, brain inflammation, blindness, hearing loss and death. Children aged 12 months to 12 years may instead receive the MMRV vaccine, which also includes the varicella (chickenpox) vaccine [1].
Is MMR a live vaccine?
Yes. It contains weakened (attenuated) live viruses. They will not give you the full-blown illness if you have a healthy immune system, but after vaccination your immune system recognizes the viruses and should have the tools to fight them off if you are exposed in the future [1].
What is the MMR vaccine schedule?
In the U.S., the Centers for Disease Control and Prevention (CDC) recommends that children get two doses of the MMR vaccine [1].
Group | Recommended timing | Notes |
Babies traveling internationally | 6 to 11 months | One dose at least two weeks before any international travel. They still get two doses at the usual ages. |
Children, first dose | 12 to 15 months | Start of the two-dose series. |
Children, second dose | 4 to 6 years | Can be given earlier, as long as it is at least 28 days after the first dose. |
Adults | Talk to your provider | If you have not had two doses of the live MMR vaccine or are unsure, your provider may suggest at least one shot, unless you have certain health conditions such as a weakened immune system. |
Adults with extra reasons | Extra doses may be advised | Working in healthcare, going to college with an unclear vaccination history, international travel, living in or traveling to an area where measles or mumps is spreading (another dose may be recommended during a mumps outbreak), or considering pregnancy with an unclear history. |
If you are not sure whether you or your child has had the MMR vaccine, a provider might suggest one or two doses just to be safe [1].
Children get two doses, and adults with no evidence of immunity may need a catch-up dose.
How effective is the MMR vaccine, and how long does it last?
Two doses of the MMR vaccine are 97% effective at preventing measles and rubella and 86% effective at preventing mumps. A small number of fully vaccinated people may still get sick if exposed, but their symptoms are usually milder and they are less likely to spread the virus to others [1].
Most people who receive the vaccine are protected for life against measles and rubella. The vaccine also protects against mumps, but some people may lose immunity to mumps over time, and you may need an additional dose during a mumps outbreak [1].
How safe is the MMR vaccine, and what are its side effects?
The MMR vaccine greatly reduces your risk of getting measles, mumps and rubella, which are highly contagious infections that can cause serious, life-threatening conditions [1].
Possible side effects
Soreness, bruising, redness and swelling at the injection site
Mild rash
Fever
Joint stiffness
Swollen lymph nodes (glands)
Diarrhea
Fatigue
Rare but serious side effects
Severe allergic reaction (anaphylaxis)
Seizures, usually due to high fever
Unusual bleeding or bruising caused by a low platelet count
When to get help right away: seek immediate medical attention for an allergic reaction or any of these serious side effects. Symptoms of an allergic reaction include hives, low blood pressure and swelling of your face, lips or tongue [1].
Most reactions are mild, and serious reactions are rare.
Who Should Not Get the MMR Vaccine?
You should not get the MMR vaccine if you [1]:
Have a weakened immune system
Are pregnant or think you might be pregnant
Have severe, life-threatening allergies to any part of the vaccine
Talk to your provider first if you [1]:
Have a health condition that makes you bleed or bruise easily, or have had one in the past
Have recently received a blood transfusion or other blood products
Need to get a tuberculosis skin or blood test
Have received any other vaccines in the last month
Have a history of seizures
If any of these apply, your provider may recommend waiting to get the vaccine. Do not hesitate to ask if you are not sure whether you should get it [1].
Pregnancy, a weakened immune system and severe allergies are the main reasons to avoid or delay the vaccine.
When should you call your provider after an MMR vaccine?
Talk to your provider or your child's provider if you have any questions about the MMR vaccine, and let them know right away if you have concerning side effects [1].
What is the bottom line on the MMR vaccine?
Vaccines often work so well that we forget why we need them. Since the MMR vaccine was introduced more than 50 years ago, we rarely see the severe effects of measles, mumps or rubella, and healthcare providers recommend it for anyone who can safely get it. It is fine to have questions, and your provider can help with any concerns about your own or your child's vaccination status [1].
Frequently Asked Questions
Can the MMR vaccine cause the diseases it is meant to prevent?
The vaccine contains weakened live viruses that will not give you the full-blown illness if you have a healthy immune system. If you have a weakened immune system, you should not get the vaccine [1].
Is there a link between the MMR vaccine and autism?
No. A nationwide Danish cohort of 657,461 children found no increased risk of autism after MMR vaccination (hazard ratio 0.93; 95% CI 0.85 to 1.02) [3], and a Cochrane review found no evidence of an association (rate ratio 0.93; 95% CI 0.85 to 1.01) [2].
What is the difference between MMR and MMRV?
MMR protects against measles, mumps and rubella. Children aged 12 months to 12 years may receive the MMRV vaccine, which also includes the varicella (chickenpox) vaccine [1].
Do adults need the MMR vaccine?
You might. If you have not had two doses of the live MMR vaccine or are unsure of your history, talk to your provider, who may suggest at least one shot unless you have a condition such as a weakened immune system. Extra doses may be recommended if you work in healthcare, go to college, travel internationally, or are in or traveling to an area where measles or mumps is spreading [1].
How long should I wait to get pregnant after the MMR vaccine?
Wait at least 28 days after the shot before getting pregnant. You should not get the vaccine if you are pregnant or think you might be [1].
What if I am not sure I was vaccinated?
If you are not sure whether you or your child has had the MMR vaccine, a provider might suggest one or two doses just to be safe [1].
How long does the MMR vaccine last?
Most people are protected for life against measles and rubella. Some people may lose immunity to mumps over time and may need an additional dose during a mumps outbreak [1].
How effective is the MMR vaccine?
Two doses are 97% effective at preventing measles and rubella and 86% effective at preventing mumps [1]. A Cochrane review found measles effectiveness of 96% after two doses [2].
What are the side effects of the MMR vaccine?
Most are mild, such as soreness at the injection site, a mild rash, fever, joint stiffness and swollen lymph nodes. Rare serious effects include anaphylaxis, seizures usually due to high fever, and unusual bleeding or bruising from a low platelet count [1].
When should I seek medical attention after the vaccine?
Seek immediate medical attention for an allergic reaction (hives, low blood pressure, or swelling of the face, lips or tongue) or any of the rare serious side effects, and tell your provider right away about concerning side effects [1].
How do I prepare for the MMR vaccine?
There is no special preparation for the shot. Before you or your child gets it, tell the provider about pregnancy or plans to become pregnant, a weakened immune system, a condition that causes easy bleeding or bruising, or a severe allergy, since these can mean the vaccine should be delayed or avoided [1].
Does the MMR shot hurt?
It is a quick injection, so you may feel a brief pinch. Afterward, soreness, bruising, redness and swelling at the injection site are common and usually mild; a mild fever can also occur [1].
Related Reading
Vaccines: How They Work, Types, Safety and Side Effects explains how vaccines work and why they matter.
Understanding the COVID-19 Vaccine: How It Works and What to Expect explains how mRNA and protein COVID-19 vaccines work, what happens at the appointment and common side effects.
References
Cleveland Clinic. MMR Vaccine. Cleveland Clinic. May 9, 2025. https://my.clevelandclinic.org/health/procedures/mmr-vaccine
Di Pietrantonj C, Rivetti A, Marchione P, Debalini MG, Demicheli V. Vaccines for measles, mumps, rubella, and varicella in children. Cochrane Database Syst Rev. 2021;11(11):CD004407. PMID 34806766. https://doi.org/10.1002/14651858.CD004407.pub5
Hviid A, Hansen JV, Frisch M, Melbye M. Measles, mumps, rubella vaccination and autism: a nationwide cohort study. Ann Intern Med. 2019;170(8):513-520. PMID 30831578. https://doi.org/10.7326/M18-2101
Medical disclaimer
This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. The clinical information in this guide reflects source material last reviewed in May 2025.
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