MMR

MMR Vaccine (Measles, Mumps, Rubella)

Content reviewed against published CDC, AAP, WHO guidelines

Editorial policy

Last reviewed:

Key takeaways

  • Prevents: Measles, Mumps
  • Schedule: 2 doses starting at 12-15 months
  • Effectiveness: One dose is 93% effective against measles, 78% against mumps, and 97% against rubella.
  • Most common side effect: Sore arm or leg

How it works

The MMR vaccine contains live but weakened (attenuated) versions of measles, mumps, and rubella viruses. These weakened viruses cannot cause the full disease but are strong enough to stimulate the immune system to produce antibodies. After vaccination, the immune system "remembers" these viruses and can fight them if exposed later.

Recommended schedule

DoseAge
Dose 112-15 months
Dose 24-6 years

Side effects

Common (mild, resolve in 1-2 days)

  • Sore arm or leg (injection site reaction)
  • Fever (up to 1 in 6 children)
  • Mild rash (about 5% of recipients, 7-12 days after vaccination)
  • Swelling of glands in cheeks or neck
  • Joint pain or stiffness (mainly in adolescent/adult females)
  • Fussiness or mild irritability

Serious (very rare)

  • Febrile seizure (about 1 in 3,000 doses — caused by the fever, not the vaccine itself)
  • Temporary low platelet count (ITP) — about 1 in 25,000 doses, usually resolves on its own
  • Severe allergic reaction (anaphylaxis) — approximately 1 in 1 million doses
  • Encephalitis — approximately 1 in 1 million doses (vs 1 in 1,000 with actual measles)

Who should NOT get this vaccine

  • Severe allergic reaction to a previous dose or vaccine component (gelatin, neomycin)
  • Severe immunodeficiency (e.g., untreated HIV with severe immunosuppression, chemotherapy, high-dose steroids)
  • Pregnancy (wait 4 weeks after vaccination before becoming pregnant)
  • Recent blood product or immunoglobulin (may need to wait 3-11 months depending on product)

Effectiveness

One dose is 93% effective against measles, 78% against mumps, and 97% against rubella. Two doses are 97% effective against measles and 88% against mumps.

Available brands

M-M-R II

Merck

Priorix

GlaxoSmithKline

Myths vs. facts

Myth: “The MMR vaccine causes autism”

Fact: This claim originated from a fraudulent 1998 study by Andrew Wakefield, which was retracted and Wakefield lost his medical license. Over 20 large studies involving millions of children across multiple countries have found NO link between MMR and autism. The timing of MMR (12-15 months) coincides with when autism signs first become apparent, creating a coincidental association.

Myth: “It's safer to get measles naturally”

Fact: Measles kills 1-2 of every 1,000 infected children and causes brain damage in 1 of every 1,000. The vaccine carries a risk of serious reaction of about 1 in 1 million. Natural measles is approximately 1,000 times more dangerous than the vaccine.

Myth: “You can split the MMR into separate shots to reduce risk”

Fact: There is no scientific evidence that separating the vaccines is safer. Delaying vaccination leaves children unprotected longer. The UK experienced measles outbreaks when parents chose to separate vaccines and then didn't complete the series.

Frequently asked questions

Can my child get measles from the MMR vaccine?
No. While about 5% of children develop a mild rash 7-12 days after vaccination, this is not measles and is not contagious. The attenuated virus in the vaccine is too weak to cause actual measles disease.
Should I delay MMR until my child is older?
No. The CDC recommends the first dose at 12-15 months because this is when maternal antibodies wane and the child becomes vulnerable. Delaying leaves your child unprotected during a period when measles can be very serious.
What about the egg allergy concern?
The MMR vaccine is grown in chick embryo cell culture, but contains such negligible amounts of egg protein that it is safe for children with egg allergies. The AAP and ACAAI confirm that egg allergy is NOT a contraindication to MMR.
My child had a febrile seizure after the first dose — should they get the second?
Usually yes. Febrile seizures are caused by fever, not the vaccine itself, and do not cause lasting harm. Discuss with your pediatrician, who may recommend acetaminophen before the second dose.

Sources

CDCAAPWHO

All content follows our editorial policy and is reviewed against published clinical guidelines.

2,705 evidence-based guides6 authoritative medical sources

Bottom line

The MMR Vaccine (Measles, Mumps, Rubella) (MMR) is safe, well-studied, and recommended by the CDC, AAP, and WHO. Talk to your pediatrician if you have questions about timing or your child's specific health needs.

Choosing to vaccinate your child is one of the most important things you can do to protect their health. If you have concerns, your pediatrician is always happy to talk through them with you.