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MMR side effects

The MMR vaccine is very safe and most side effects are mild and short-lived.

Because the MMR vaccine combines three separate vaccines in one injection, each vaccine can cause different side effects that can happen at different times.

There's less chance of side effects after the second dose of MMR than the first.

Common side effects of the MMR vaccine

About one week to 11 days after the MMR injection, some children get a very mild form of measles. This includes a rash, high temperature, loss of appetite and a general feeling of being unwell for about two or three days.

About three to four weeks after having the MMR injection, one in 50 children develop a mild form of mumps. This includes swelling of the glands in the cheek, neck or under the jaw, and lasts for a day or two.

One to three weeks after receiving the rubella vaccine component of MMR vaccine, some adult women experience painful, stiff or swollen joints, which can last for around three days.

Rare side effects of the MMR vaccine

Bruise-like spots

In rare cases, a child may get a small rash of bruise-like spots about two weeks after having the MMR vaccine. This side effect is linked to the rubella vaccine and is known as idiopathic thrombocytopenic purpura (ITP).

It's been estimated that ITP develops in one in every 24,000 doses of the MMR vaccine given. There is a greater risk of developing ITP from measles or rubella infection than there is from having the vaccine. ITP usually gets better without treatment but, as with any rash, you should seek advice from your GP as soon as possible.

Seizures (fits)

There is a small chance of seizures (fits) occurring six to 11 days after having the MMR vaccine. It sounds alarming, but it's rare, and only happens in only about one in every 1,000 doses. In fact MMR-related seizures are less frequent than seizures that occur as a direct result of a measles infection.

Allergic reaction

In extremely rare cases, a child can have a severe allergic reaction (known medically as anaphylaxis) immediately after having the MMR vaccine. Again it's an alarming prospect, but if the child is treated quickly, they make a full recovery. Medical staff who give vaccines are trained to deal with allergic reactions.

Monitoring safety and side effects of the MMR vaccine

The Yellow Card Scheme allows you to report suspected side effects from any medicine you are taking. It is run by a medicines safety watchdog called the Medicines and Healthcare products Regulatory Agency (MHRA).

Last Updated: 17/02/2022 16:06:10
The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website