Severe or disputed reactions to MMR

Most children who have the MMR vaccine do not have any problems with it or if reactions do occur they are usually mild. (See 'No Reaction to MMR'). The overwhelming majority of parents believe in immunisation for their children. We have however included here the views of a few parents who do not believe immunisation is right for their own child based on their personal beliefs. Their views represent a small proportion of the population.

Like any medicine, a vaccine is occasionally capable of causing serious problems. We know that these problems are extremely rare. For example, severe allergic reactions* (anaphylaxis) - in the UK between 1997 and 2003 there were a total of 130 reports of anaphylaxis following ALL immunisations. Around 117 million doses of vaccines were given in the UK during this period. This means that the overall rate of anaphylaxis is around 1 in 900,000. (Oxford University - Oxford Vaccine Group June 2019).

Several other problems have been reported to occur after a child gets MMR vaccine. However, as these problems can happen for other causes and also occur in non-immunised children, it is rarely possible to know if the vaccine caused the problem in an individual child. These are sometimes referred to as disputed reactions. One way in which experts find out whether a vaccine causes a problem is to carry out studies of whole populations to see if the risk of severe problems is commoner in children who have or have not been immunised. Before making a decision, parents and professionals need also to know about problems from the disease and balance these against any risk from immunisation (see 'Parents' views of the diseases').

In 1998, research by Wakefield et al suggested a possible link between MMR, inflammatory bowel disease and autism. Since 1998, these research findings have been discredited by many other scientific studies, which have produced good scientific evidence to suggest there is not a link between MMR, inflammatory bowel disease and autism. The study by Wakefield et al was based on only eight children, with speculative findings that have now been discredited by most of the team that produced it and the editor of the Lancet.

However, a very small number of parents of children who had developed severe symptoms at the same time that their child received the MMR vaccine contest these findings and have a strong personal belief that MMR triggered these symptoms in their child.  

These parents talked about the symptoms that their children had shortly after their MMR vaccine and why they believed their child's symptoms were triggered by the MMR vaccine.  

One mother explained that her 8-year-old son had received his MMR vaccine when he was 13 months old and a couple of hours afterwards he developed agitation which lasted a couple of weeks, after which he had several petit mal epileptic episodes and stopped making any attempt to speak. He was diagnosed as having viral encephalitis. As he got older, he was also diagnosed with autism and epilepsy.

One father talked about the changes that had occurred in his daughter five days after she had the MMR vaccine. She had episodic symptoms where she stammered, her eye movement changed, her language and speech regressed, she was reluctant to make eye contact and she had a rash on her face. A doctor at the hospital described it as post viral encephalitis. Over the next few days she became detached and no longer wanted to play or dress up. 

Three months after the MMR vaccine, more of her old self was coming back but she still had a stammer. He also said that retrospectively they had realised that there had been some mild changes in their son's behaviour at the time he had his MMR vaccine, but felt that in his son's case there was no evidence for a link.

One couple explained that two days after their 7-year-old son had his MMR vaccine when he was thirteen months old, he developed a temperature, skin eruptions, a hacking cough and lost his appetite. After two weeks he continued to have little appetite, became socially withdrawn and started showing other symptoms of autism, and he was later diagnosed with onset regressive autism. They also said that they had noticed some changes in their older son's behaviour when he was thirteen months old that remain today. He has not been diagnosed with autism but he has a tendency to be literal about things and to struggle sometimes in social situations and understand why other children do what they do.

*A serious allergic reaction (less than one in a million doses); this would occur within a few hours of the immunisation, and the signs would be wheezing or difficulty with breathing, a rash (like a nettle sting), paleness, being floppy, and/or a fast heart beat. Seek medical advice immediately.

Last reviewed August 2019.
Last updated August 2019.


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