MMR vaccine

What is the MMR vaccine?

The MMR vaccine is an injection that prevents your child from catching measles, mumps and rubella. Although most people usually recover from these illnesses, each one can be unpleasant and have serious consequences. 

  • Measles is highly infectious and may cause complications such as diarrhoea, ear infections, pneumonia and encephalitis (inflammation of the brain).
  • Mumps is also infectious and can cause complications such as meningitis and deafness. It may also cause inflammation of your pancreas. In boys, it can damage the testicles and cause infertility. In girls, it can cause swelling of the ovaries.
  • Rubella (German measles) is usually a mild illness however, it can be harmful to pregnant women. If you become infected in the first 16 weeks of pregnancy, it’s very likely to affect your unborn baby. It can cause blindness, deafness, brain damage and heart damage to your baby. Rubella can also lead to miscarriage. If you become infected within 16 and 20 weeks of pregnancy, there is a risk that your baby will be deaf. After 20 weeks, there is no increased risk.

The MMR vaccine can prevent each of these illnesses.

How does the MMR vaccine work?

The MMR vaccine is made from weakened forms of each of the measles, mumps and rubella viruses. This vaccine stimulates your child’s immune system to respond and remember the viruses. This means that if your child gets infected with one of the three viruses, his or her immune system will recognise the virus and act to prevent infection.

When is the MMR vaccine given?

The MMR vaccine is usually given to children who have the first injection between 12 to 13 months old. A second dose is given between the ages of three and five years old to protect any children who haven’t responded to the first dose.

If a child needs to be protected against measles quickly, for example, during a measles outbreak, they can have the second dose of the MMR vaccine one month after the first dose. However, if they have the second dose before they reach the age of 18 months, they should still receive the routine dose when they reach three to five years old, before they start school.

The MMR vaccine can be offered to young people when they leave school or before they enter further education if they haven’t already had both doses.

If you aren’t already immune to rubella, you will be offered the MMR vaccine if:

  • you’re a woman of childbearing age
  • you’re a healthcare worker who may come into contact with pregnant women
  • you have just had a baby

Talk to your GP about the MMR vaccine if you’re thinking about becoming pregnant and if you have never had rubella or the MMR vaccination.

The MMR vaccine can be given at any age. It’s not dangerous to receive the MMR vaccine more than once. If you can’t remember whether or not you have had it, ask your GP.

Is the MMR vaccine effective?

After the first dose of the MMR vaccine, 64 out of 100 people will be protected against mumps, 90 out of 100 people will be protected against measles and 95 out of 100 people will be protected against rubella. After the second dose, 99 out of 100 people will be protected against all three illnesses.

Since the MMR vaccine was introduced in the UK in 1988, the number of children catching measles, mumps and rubella has fallen. The introduction of the vaccine has also led to a drop in the number of babies born with serious disabilities caused when their mothers developed rubella during pregnancy.

Special care

Most people can have the MMR vaccine, but there are some who shouldn’t. These include: 

  • people who take medicines that lower their immune system’s response or who have a weakened immune system because of an illness such as HIV/AIDS or cancer
  • anyone who has had an anaphylactic reaction to gelatine or the antibiotics kanamycin and neomycin
  • anyone who has had a confirmed anaphylactic reaction to a previous dose of a measles, mumps or rubella vaccine
  • pregnant women

Some people may get minor allergic reactions to the vaccine. However, this shouldn't stop people from having the MMR vaccine in the future. Anaphylaxis is a severe allergic reaction in which the tongue or the back of the throat may swell and is extremely rare with this vaccine.

Your GP may advise to postpone you or your child's MMR vaccine until a later date, if:

  • you or your child have had another live vaccine within the previous four weeks
  • you or your child have a fever

Talk to your GP or nurse if you’re not sure whether you or your child should have the MMR vaccine.

Side-effects and safety

Side-effects are the unwanted but mostly mild and temporary effects of the vaccination. They’re usually rare after the first dose and even less likely after the second. 

The three viruses in the vaccine act at different times and may produce different side-effects as they start to work.

The measles part of the vaccine starts to work six to 11 days after immunisation. Your child may have a fever or develop a measles-like rash that usually lasts two to three days. You can give your child a dose of junior paracetamol if he or she develops a fever, but if the fever persists, contact your child’s GP. Children who get vaccine-related symptoms aren't infectious to others.

About one in every 1,000 immunised children may have a fit caused by the fever. This is called a febrile convulsion. However, the number of febrile convulsions caused by measles is much higher than the number the MMR vaccine may cause.

It’s rare, but your child may get mild symptoms similar to mumps (fever and swollen glands) about two to three weeks after the MMR vaccine, when the mumps part of the vaccine starts to work.

Children may get a rash of small bruise-like spots in the first six weeks after the vaccination, but this is also very rare. It can be caused by the measles or rubella parts of the vaccine. Take your child to his or her GP if you see spots like these.

Fewer than one child in a million develops encephalitis (inflammation of the brain) after the MMR vaccine. If a child who hasn’t been vaccinated catches measles, the chance is higher – between one in 200 and one in 5,000.

Side-effects of the vaccine are usually mild and, most importantly, they are milder than the potentially serious consequences of having measles, mumps or rubella. If you’re concerned about any of your child’s symptoms, see your GP.

Egg allergy and the MMR vaccine

The MMR vaccine is made using a protein related to egg. However, evidence shows that it’s safe to give the vaccine to nearly all children, even those who have a very severe reaction to eggs.

If your child has a severe egg allergy, let your GP or nurse know. He or she can make special arrangements to give your child the MMR vaccine safely, in hospital if necessary.

Autism and bowel disease

You may have heard of a suggested link between the MMR vaccine and autism and bowel disease. However, there is a great deal of scientific evidence available, based on records of millions of MMR vaccinations that shows no connection between them.

A link between the MMR vaccination and autism was suggested in 1998 when a group of doctors published a paper about 12 autistic children who also had bowel problems. The doctors put forward a theory about bowel inflammation, caused by the MMR vaccine, which could lead to problems with brain development. The researchers didn’t prove their theory and they actually stated in their paper that they had not proved a link between autism and the MMR vaccine. However, the resulting media attention gave the impression that there was one. This led to some parents whose children were born after 1999 to decide not to give them the vaccine.

If your child has autism, you will usually start to notice signs when he or she is around one to two years old. As the MMR injection is given at around this age, it’s easy to understand why some parents thought there might be a link.

Single vaccines

Where the MMR vaccine is available, no country recommends single rather than combined vaccines.

There are a number of reasons why the vaccines in the combined MMR aren’t routinely given separately in the UK.

  • Children would need to have six injections in total, which is more unpleasant because of the pain from each jab and six episodes of possible side-effects.
  • It could mean that fewer children have all the necessary vaccinations, increasing the level of measles, mumps and rubella in the UK.
  • There may be more delay before being completely vaccinated, leaving children at risk of infection from the diseases for longer.
  • Single vaccines aren’t licensed in the UK and haven't passed UK safety and effectiveness testing.

If you or your child has had a single vaccine in the past for measles, mumps or rubella, having the full MMR vaccine at a later date will cause no harm. It’s recommended to wait at least four weeks from when you have a single vaccine until you have the MMR vaccine.

Do I need to have an MMR vaccination to travel abroad?


Measles, mumps and rubella are contagious illnesses that occur throughout the world. In some countries, children aren’t routinely vaccinated with the MMR vaccine and outbreaks of these illnesses are more common than in the UK. If you haven’t been immunised with the MMR vaccine, you should have it before you travel. This will protect you from these illnesses and also prevent you bringing them back to the UK and spreading them further.


All three diseases, in particular measles, need a large number of people to be immunised for the whole population to be protected. This is known as herd immunity. However, in many countries this doesn’t happen and outbreaks of the diseases are common. This means that although you may be unlikely to catch measles, mumps or rubella in the UK, you may be at risk if you travel abroad and haven’t been immunised against these diseases.

Africa and South-East Asia are the most badly affected areas because few people are immunised against the diseases in these areas.

Every year, people from the UK who haven’t been immunised catch measles, mumps or rubella while they are abroad. These diseases may then be brought back to the UK where they may spread further. The Health Protection Agency recommends that you should find out whether you have had the MMR vaccination before you travel. If you haven’t, you can make an appointment with your GP or nurse to have it. This is particularly important if you’re travelling to areas of the world where few people are immunised and outbreaks of these disease occur.

If you’re pregnant, or there is a chance that you may become pregnant while you’re travelling, it’s very important to have the vaccination before you go away, if you’re not already immune to rubella.

If your child is less than six months old and is travelling to an area where measles is common or where there is a current outbreak, it’s recommended that they should receive the MMR vaccine early. They should still continue to have a further two doses of the vaccine as part of the routine vaccine schedule.

Older children who are travelling who have received only one dose of MMR at the routine age of 13 months should have the second dose brought forward to at least one month after the first. If your child is 18 months or younger when the second dose is given, then the routine pre-school dose should continue to be given in order to ensure full protection.

Why are two doses of MMR needed?


After the first dose of the MMR vaccine, most, but not all, children develop immunity to measles, mumps and rubella. Because there are still some children who don’t have immunity after the first dose, a second dose is given. After this almost all of the children who didn’t have immunity after the first dose will develop it.


When your child is immunised against measles, mumps and rubella, he or she will have two vaccinations. The first is given to your baby at around 13 months and the second ‘booster’ is given when your child is between three and five years old, before he or she starts school, where they will be mixing with lots of new children and there is a greater risk of catching these diseases. Having two doses of MMR will ensure that your child is fully protected against measles.

There are also some children who may miss the first immunisation when they are babies. The second booster gives you a chance to have your child immunised before he or she starts school and will boost immunity of children who have already been immunised.

Why doesn’t the NHS offer single vaccines of measles, mumps and rubella?


The NHS doesn’t offer single vaccines because they haven’t been properly researched or tested to see how safe they are and how well they work, whereas the MMR vaccine has. Single vaccines aren’t recommended because they could put babies and children at an increased risk of getting measles, mumps and rubella.


Stories in the media have raised concerns about a possible link between the MMR vaccine, autism and bowel disease. Although there is a great deal of scientific evidence from around the world that shows no connection between these condition and the MMR vaccine, many parents are still concerned and have looked for alternatives. One of these is to give single vaccines of measles, mumps and rubella.

Single vaccines for mumps and measles aren’t licensed in the UK. This means that the vaccines don’t undergo any testing in the UK to see how safe they are or how well they work. There is no research to show how they should be given or how much of a gap is needed between injections. However, there is a lot of research to prove the safety and effectiveness of the MMR vaccine.

Single vaccines could put babies and children at greater risk of measles, mumps and rubella. If you decide that your child should have single vaccines, he or she will need to have a total of six injections. Not only does this mean more injections, which many children may find upsetting, but also a much bigger gap between injections during which your child could catch any of the diseases.