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MMR Vaccine

Measles, mumps, and rubella combination vaccine

Quick Summary

MMR Vaccine

Combines protection against measles, mumps, and rubella in a single injection.

Required for school Publicly funded
Diseases Protected Against
Measles, mumps, and rubella (German measles)
Ontario Routine Timing
First dose at 12 months. A second dose of measles, mumps, and rubella protection is given at 4–6 years, usually as MMRV (which also includes varicella).
Number of Doses
Two doses of measles-mumps-rubella-containing vaccine in childhood
Publicly Funded Status
Yes — provided free of charge as part of Ontario's routine schedule
Bottom line: The MMR vaccine protects against three diseases that were once very common in childhood. Measles, mumps, and rubella are all required for school attendance under Ontario law (unless a valid exemption applies). The first dose is given at age 1, with a second dose at 4–6 years (usually given as the combined MMRV vaccine).
The Diseases

What it protects against

The MMR vaccine protects against three separate diseases. Here's what each one is and why it matters.

Disease What parents might notice How it spreads Why it can be serious How vaccination helps
Measles High fever, cough, runny nose, red and watery eyes, followed by a red blotchy rash that usually starts on the face. Through the air and by contact — measles is one of the most contagious known diseases, and can linger in a room after an infected person leaves. Can lead to ear infections, pneumonia, and, less commonly, brain swelling (encephalitis) or, rarely, death. Complications are more common in young children. The vaccine prompts the immune system to recognize the measles virus, providing strong protection after two doses.
Mumps Fever, headache, muscle aches, tiredness, and swelling of the salivary glands, giving puffy cheeks and a swollen jaw. Saliva and respiratory droplets — coughing, sneezing, and close contact. Can lead to complications such as inflammation of the testicles or ovaries, inflammation of the brain or its lining, and, in rare cases, hearing loss. The vaccine helps the immune system recognize and respond to the mumps virus.
Rubella (German measles) Often mild — a low fever and a rash. Some people, especially children, may have no obvious symptoms. Coughing, sneezing, and close contact. The greatest danger is to pregnancy: rubella infection in early pregnancy can cause serious birth defects (congenital rubella syndrome). Protecting children helps protect pregnant people in the community. The vaccine helps prevent rubella infection and reduces its spread, which protects vulnerable pregnancies.
Timing & Schedule

Why it's given at this age

Why at 12 months? Babies receive some temporary protection against measles from their birthing parent, which can interfere with how well the vaccine works if given too early. By around 12 months, this passed-on protection has usually faded enough for the baby's own immune system to respond well to the vaccine. This is why the first dose is generally given at the first birthday rather than earlier.

Why two doses? One dose provides good protection, but a small percentage of children do not respond fully to the first dose. The second dose helps ensure protection for those children and strengthens it overall. After two doses, protection against measles is very high.

What if a dose is late? If the second dose is delayed, the series does not need to restart — the next dose can generally be given at the next opportunity, following minimum spacing guidelines. A healthcare provider or your local public health unit can confirm the right timing. See the Catch-Up & Missing Records page.

Can it be given with other vaccines? Yes. At the 12-month visit, MMR is routinely given alongside other scheduled vaccines such as pneumococcal conjugate and meningococcal C. Live vaccines like MMR have specific timing considerations relative to certain other live vaccines and to some medical treatments — a healthcare provider can advise if this applies to your child.

A note on early travel doses: In some situations, such as international travel to an area where measles is common, a healthcare provider may recommend an early dose of measles-containing vaccine for an infant younger than 12 months. This is a special circumstance — speak with a healthcare provider or travel clinic if this may apply to your family.
Ontario School & Reporting Status

School and reporting status

Measles, mumps, and rubella are all required for school attendance. Under the Immunization of School Pupils Act (ISPA), Ontario requires immunization against measles, mumps, and rubella for school attendance, unless a valid medical or non-medical exemption is on file. The MMR vaccine provides protection against all three in a single injection.

This means MMR is one of the more straightforward vaccines when it comes to school requirements — all three diseases it protects against are on the ISPA list, so there is no "partly required" nuance as there is with some combination vaccines.

Reporting: As with all vaccines, parents and caregivers are generally responsible for reporting their child's immunizations to their local public health unit. Healthcare providers do not always do this automatically. After each dose, make sure your provider updates your child's immunization record (the "yellow card"), and report the update to your local public health unit — for example, through Immunization Connect Ontario (ICON) if your area uses it.

Second dose as MMRV: In Ontario, the second dose of measles-mumps-rubella protection is usually given at 4–6 years as the combined MMRV vaccine, which also includes varicella (chickenpox). See the MMRV profile for details on that combination.

Exemptions: If your child cannot receive this vaccine for medical reasons, or you are seeking a non-medical exemption based on conscience or religious belief, see the School Requirements hub for the exemption process.

Ingredient Transparency

What's in this vaccine

Two MMR products are authorized for use in Canada: Priorix® (GSK) and M-M-R® II (Merck). Either may be used depending on supply. The information below reflects Priorix®, based on its Health Canada product monograph; M-M-R II contains similar categories of ingredients. The MMR vaccine is a live attenuated vaccine, meaning it contains weakened forms of the viruses that cannot cause the diseases in healthy people.

Ingredient / Component Category Why it's there Plain-English explanation
Live attenuated measles, mumps, and rubella viruses Active ingredients These are weakened forms of the three viruses that train the immune system to recognize them. "Attenuated" means weakened. These viruses are weakened enough that they don't cause the diseases in healthy people, but they still teach the immune system how to respond if exposed to the real viruses later.
Amino acids Stabilizer / growth component Support the growth of the vaccine viruses and help keep the vaccine stable. Amino acids are the building blocks of proteins and are found throughout the body and in food.
Lactose Stabilizer Helps keep the vaccine stable, particularly during freeze-drying. A sugar found naturally in milk, used here in a small amount as a stabilizer.
Mannitol and sorbitol Stabilizers Help protect the vaccine viruses and keep the product stable. These are sugar alcohols used as stabilizers in many foods and medications.
Neomycin (trace amounts) Manufacturing process residual (antibiotic) Used during manufacturing to help prevent bacterial contamination of the cell cultures. A trace amount of this antibiotic may remain. This is relevant for individuals with a known severe allergy to neomycin — discuss this with a healthcare provider if it applies to your child.
Water for injection (diluent) Diluent Used to reconstitute the freeze-dried vaccine before injection. Sterile water used to mix the vaccine into its final form just before it's given.
About egg allergy: The measles and mumps components are grown using chick-embryo cell cultures. Despite this, major medical and public health bodies note that MMR can generally be given to children with egg allergy, as the amount of egg protein is negligible. If your child has a severe egg allergy or a history of severe allergic reactions, discuss it with a healthcare provider, who can advise on any precautions.
A note on the rumour about MMR and autism: The claim that MMR causes autism originated from a study that was later found to be seriously flawed and was retracted, and its author lost his medical license. Many large, high-quality studies since then, involving millions of children, have found no link between the MMR vaccine and autism. This is covered in more depth in the "What the evidence shows" section below.
Side Effects & Safety

Side effects and safety

Expected / common side effects

  • Soreness, redness, or swelling where the needle was given
  • Mild fever
  • A mild rash, sometimes measles-like
  • Temporary swelling of glands in the cheeks or neck
  • Fussiness or tiredness

Timing and duration: Because MMR is a live vaccine, some reactions appear later than with other vaccines — typically about 1 to 2 weeks after the dose, when the weakened viruses prompt an immune response. A mild fever or rash around this time is expected and usually passes within a few days. It is not contagious in the way a true infection would be.

Home care: A cool compress can ease injection-site soreness. Acetaminophen or ibuprofen may be used as directed for fever or discomfort — check with a pharmacist or healthcare provider on appropriate dosing. Children under 19 should not be given ASA (Aspirin) or salicylate-containing products.

When to call a healthcare provider: If a fever is high or persistent, if your child seems unusually unwell, or if you're unsure — it's always reasonable to call.

Mild side effects can happen as the immune system responds. Many children have no side effects at all, and that does not mean the vaccine didn't work.

Rare but important

  • Severe allergic reaction (anaphylaxis) — reported rarely after vaccination in general; exact frequency varies by source.
  • Febrile seizure — a seizure triggered by fever, which can happen with any fever-causing illness or vaccine. Uncommon, usually brief, and typically not associated with long-term effects.
  • Temporary drop in platelets (a type of blood cell involved in clotting) — rare, usually temporary, and generally resolves on its own.

What clinics do to reduce risk: Clinics ask about allergy history before vaccination and are equipped with epinephrine and trained staff in case of a severe allergic reaction.

Observation period: Many clinics recommend staying nearby for about 15 minutes after vaccination, as severe allergic reactions — though rare — typically occur shortly after the injection.

Get urgent help now if your child has:

  • Trouble breathing
  • Swelling of the lips, tongue, throat, or face
  • Widespread hives together with breathing difficulty
  • Severe weakness, limpness, or unresponsiveness
  • A seizure
  • Persistent, inconsolable crying that won't settle, or you are very worried
  • A high or persistent fever, especially in a young infant
  • Any symptom that feels serious or is rapidly getting worse

If any of these occur, go to the nearest emergency department or call 911. Otherwise, contact a healthcare provider and let them know what happened — this information also helps with vaccine safety monitoring.

Before the Appointment

Who should pause or speak with a healthcare provider first

Speak with a healthcare provider before this vaccine if:

  • Your child has had a serious allergic reaction to a previous dose of MMR, or to any of its components (including neomycin)
  • Your child has a weakened immune system — for example, due to certain medical conditions, or treatments like chemotherapy or high-dose steroids. As a live vaccine, MMR may not be recommended, or may need specialist input, in this situation
  • Your child is pregnant (relevant for adolescents) — MMR is not given during pregnancy
  • Your child has recently received blood products or immune globulin — these can affect how well a live vaccine works, so timing may need to be adjusted
  • Your child has a moderate or severe acute illness (it's generally fine to wait until they feel better)

These usually do NOT require delaying this vaccine:

  • A mild cold or other minor illness without fever
  • Egg allergy (MMR can generally be given — see the note in the ingredients section)
  • Currently breastfeeding
  • A stable, ongoing chronic health condition
  • Currently taking antibiotics for an unrelated condition
  • A family history of seizures or of autism
Common Questions

Questions parents often ask

Yes. At the 12-month visit, MMR is routinely given alongside other scheduled vaccines such as pneumococcal conjugate and meningococcal C. There are some specific timing considerations between different live vaccines — a healthcare provider will manage this.
Being behind does not mean starting the series over. The remaining doses can generally be given following minimum spacing guidelines. Visit the Catch-Up & Missing Records page, or speak with a healthcare provider to confirm the right plan for your child.
Generally, no. A mild cold without fever is usually not a reason to delay. If your child has a fever or seems more unwell, it's reasonable to mention this to the clinic — they can advise whether to proceed or reschedule.
This is a recognized, expected reaction to MMR. Because it's a live vaccine, a mild fever and sometimes a measles-like rash can appear about 1 to 2 weeks after the dose, as the immune system responds. It usually passes within a few days. As always, if the fever is high or persistent, or your child seems unusually unwell, contact a healthcare provider.
This is common and manageable. Gather whatever records you have, and contact your local public health unit or healthcare provider — they can often help locate or reconstruct records, or advise on next steps if records truly cannot be found. See the Catch-Up & Missing Records page.
This vaccine is typically given by a family doctor or nurse practitioner as part of routine infant well-child visits. Some public health units also offer immunization clinics. See the Resources page for links to find services in your area.
Parents and caregivers are generally responsible for reporting vaccines to their local public health unit — healthcare providers do not always do this automatically. Many areas use Immunization Connect Ontario (ICON) for this. See the Resources page for links.
Mild soreness, redness, fussiness, or a low fever for a day or two are common and expected. Review the "Get urgent help now" list above — if any of those signs occur, seek urgent care. Otherwise, contact a healthcare provider with any concerns.
What the Evidence Shows

What we know about development and vaccines

Fact Large, high-quality studies involving millions of children across many countries have found no link between the MMR vaccine and autism.
Concern Many parents have heard the claim that MMR might cause autism. This is one of the most common and understandable worries, because the timing of the first MMR dose (around age 1) can overlap with when early signs of autism are sometimes first noticed.
Evidence The original claim came from a small 1998 study that was later found to have serious methodological and ethical problems. It was formally retracted by the journal that published it, and its lead author lost his medical license. In the years since, many large independent studies have looked specifically for a connection and found none. The overlap in timing reflects coincidence, not cause — autism's early signs tend to emerge in the same age range regardless of vaccination.
Takeaway The scientific consensus, based on extensive evidence, is that MMR does not cause autism. If you have questions or concerns about your child's development, a healthcare provider can be a helpful partner in addressing them — and those questions don't need to delay protection against measles, mumps, and rubella.
Fact Measles has been making a resurgence in some communities, including in Canada, particularly where vaccination rates have dropped.
Concern Some parents wonder whether measles is really serious enough to vaccinate against, since many people think of it as a routine childhood illness of the past.
Evidence Measles is one of the most contagious diseases known. While many children recover, a meaningful number develop complications such as pneumonia or, less commonly, brain swelling. It can be especially dangerous for infants too young to be vaccinated and for people with weakened immune systems, who rely on high community vaccination rates for protection.
Takeaway Vaccination protects not only your own child but also more vulnerable people in the community who cannot be vaccinated themselves.
Ontario Next Steps

What to do next

Where to get it

Typically given by a family doctor or nurse practitioner during routine well-child visits. Some public health units also offer clinics.

What to bring

Your child's immunization record (the "yellow card"), health card if available, and a list of any allergies or previous reactions.

If you're behind

Catching up does not mean restarting. Visit the Catch-Up & Missing Records page or ask your provider for a review.

If records are missing

Contact your local public health unit — they may have records on file, or can advise on next steps.

If vaccinated outside Ontario

Bring any available records to a healthcare provider for review — products and schedules elsewhere may differ slightly from Ontario's.

Contact public health

For record reporting, school requirements, or general questions, see the Resources page for your local public health unit's contact details.

Sources

Where this information comes from

This page is based on:

Last reviewed: June 2026  ·  Next review due: December 2026
Schedules, products, and eligibility can change. Always confirm current details with your healthcare provider, your local public health unit, or official Ontario sources.

Please note: This is an independent website. It is not affiliated with, endorsed by, or operated by the Government of Ontario, the Ministry of Health, or any public health unit. The information here is for general education only and is not medical advice — always consult a licensed healthcare provider about your or your child's immunizations.