Skip to content

Measles, mumps, rubella and varicella (MMRV and MMR) containing vaccines - MMRV and MMR safety and effectiveness

The MMR-containing vaccines (MMRV and MMR) have weakened types of live viruses. All medicines and vaccines have passed strict safety standards for use in the UK and are very safe.

As with all medicines and vaccines, any reports of side effects are closely monitored and reviewed.

Side effects

Like all medicines, vaccines can cause side effects, but not everyone gets them. Most side effects are mild and may last a day or two. Side effects are usually less common after the second dose. 

The most common side effects include

  • soreness, redness and swelling or bruising at the site of the injection 
  • a fever 
  • rash, and 
  • irritability

The weakened viruses in the MMR-containing vaccines can act at different times. Side effects such as a fever and a rash are more common after the first dose. These can occur:  

  • About 6 – 11 days after the vaccine (from the measles part) 
  • About 2 – 3 weeks after the vaccine (from the mumps and rubella parts) 
  • About 3 – 4 weeks after the vaccine (from the chickenpox part) 

A small chickenpox rash may appear near the injection site after the MMRV vaccine. Children can still go to school or childcare, but any spots should be covered as a precaution.  

Very rare side effects

Very rarely, children may develop a widespread chickenpox-like rash. If this happens, anyone with a weakened immune system who has had close contact with the child should get medical advice. 

Fits (seizures) can happen when a child develops a high temperature caused by any common childhood illness, such as chickenpox. These usually do not last long and do not cause long-term health problems. After the first dose of the MMRV vaccine, children may have a brief fit caused by a fever. This is rare and happens in around one in 1,000 children. These fits are not usually harmful but need medical attention. For comparison, around one in 43 children who catch measles will have fits caused by a fever. 

Swelling in the brain (encephalitis) has been reported extremely rarely after the MMRV vaccination (less than one child in a million). However, if a child who has not been vaccinated catches measles, the chance of having encephalitis is between one in 200 and one in 5,000. 

Get medical help immediately if your child has had any of the following symptoms: 

  • Fits (seizures) 
  • Fainting  
  • Reduced alertness 
  • Loss of body control, along with a fever and headache  

If you seek medical help, let them know that your child has had the MMRV vaccine. 

Rarely, people can have a severe reaction soon after the vaccination, which causes breathing difficulties and may cause them to collapse. This is called an anaphylactic reaction, and it can also happen with other medicines and food. These reactions are extremely rare, affecting less than one in a million people. Staff who give vaccinations are trained to manage these reactions.  

People who have an anaphylactic reaction can be successfully treated and usually recover within a few hours.   

For most people, the benefits of getting vaccinated are much greater than the risks of being unprotected.

Find out more about side effects

All side effects are included in the patient information leaflet for the vaccine. For more information on side effects, go to: 

MMRV vaccine 

MMR vaccine 

If you have any questions about side effects, you can ask the person giving you the vaccine.    

If symptoms get worse or if you are concerned, Trust your instincts – get medical help immediately. Call NHS 111 Wales on 111 or your GP surgery. Calls to NHS 111 Wales are free from landlines and mobile phones.

You should report suspected side effects of vaccines and medicines online, by downloading the Yellow Card app, or by calling 0800 731 6789 (Monday to Friday, 9am to 5pm). 

Is it possible to get measles, mumps, rubella or chickenpox after being vaccinated?

Vaccination is one of the most effective ways to prevent severe illness from measles, mumps, rubella and chickenpox. No vaccine is 100% effective, so it is still important to know the signs and symptoms of these diseases, even if you or your child are vaccinated.

Is there a link between MMR-containing vaccines and autism?

You should not worry about this. There is no evidence of a link between MMR-containing vaccines and autism.   

The National Autistic Society says “there is no link between autism and vaccines”. There are many studies that have investigated this. The University of Oxford Vaccine Knowledge has a website of MMR studies for you to look at.  

Page last reviewed: 20th January 2026