The MMR vaccine and autism

The decision to immunise your child is never simple. Information on immunisation can often be confusing, and made worse by the stories you may have seen in the press and on TV. This has particularly been the case for the combined measles-mumps-rubella vaccine (commonly known as the MMR vaccine). The MMR vaccine is a combination vaccine that protects children from measles, mumps, and rubella (also known as German measles). The first dose of the vaccine is usually given to children when they are 12 to 15 months old. The second dose is usually given around 4 years of age. 

The MMR vaccine is important because it protects children against dangerous, and sometimes deadly, diseases. Because signs of autism may appear at around the same time children receive the MMR vaccine, some parents may worry that the vaccine causes autism. However, carefully performed scientific studies have found no evidence to suggest that the MMR vaccine may cause autism. Hence, individual doctors and their professional bodies (such as the Royal College of General Practitioners) continue to recommend that children have the MMR vaccine.

What is autism? 

Autism is a group of developmental disorders in which individuals have impairments in social interaction and communication skills, along with a tendency to have repetitive behaviours or interests. The severity of autism varies greatly, from individuals with little speech and poor daily living skills, to others who function well in most settings. Autism is typically diagnosed during the toddler or preschool years, although some children are diagnosed at older ages. 

Does the MMR vaccine cause autism? 

Current scientific evidence does not support the theory that the MMR vaccine, or any combination of vaccines, causes the development of autism. The question about a possible link between MMR vaccine and autism has been extensively reviewed by several independent groups of experts across the world. None has found a causal link between the MMR vaccine and autism. 

What have studies found regarding MMR vaccine and autism? 

Several large studies have shown no relationship between MMR vaccination in children and the development of autism. For example, researchers in the UK studied the records of 498 children with autism born between 1979 and 1998. They found that the percentage of children with autism who received MMR vaccine was the same as the percentage of unaffected children in the region who received MMR vaccine. They also found that there was no difference in the age of diagnosis of autism in vaccinated and unvaccinated children. 

Are there studies that suggest that the MMR vaccine can cause autism?

The existing studies that suggest that the MMR vaccine can cause autism have generated substantial media attention. However, these studies all have major weaknesses and are far outweighed by other studies that have consistently failed to show a causal relationship between MMR vaccine and autism.

What about the claim that autism increased after the MMR vaccine was introduced? 

Even if we accept that a true increase in autism has occurred, the increase could well be due to changes in diagnostic methods, diagnostic categorization, and improved identification of individuals with autism. Receiving the MMR vaccine is not a factor. If it were a factor, we would expect the increase in the level of MMR immunisation to be very similar to the autism case numbers, but this is not the case.

What about single vaccines? 

Because of concerns about the use of the combined MMR vaccine and the belief that children's immune systems cannot cope with three vaccines given together, many parents have chosen to have their children immunised with single vaccines. However, there are no benefits from separating the MMR vaccine into its individual components. 

The issue of single vaccines and immune dysfunction was addressed by a study carried out in America in 2002 by the Institute of Medicine's Immunization Safety Review Committee. This study concluded that a review of the available scientific evidence does not support the suggestion that the infant immune system is inherently incapable of handling the number of antigens that children are exposed to during routine immunizations. 

Splitting the MMR vaccine into three separate doses given at three different times would cause more discomfort from additional injections and would leave children exposed to potentially serious diseases. Furthermore, children would have to have another three injections around the age of four years, when their booster vaccinations became due. 

Should a younger sibling of an autistic child, or a child of someone who has autism be vaccinated with MMR or other vaccines? 

Yes. Current scientific evidence does not show that MMR vaccine, or any combination of vaccines, causes the development of autism, including regressive forms of autism. A younger sibling or the child of someone who suffered a vaccine side effect usually can, and should, safely receive the same vaccine.

Should we delay vaccination until we know more about the side effects of vaccines? 

No. There is no convincing evidence that vaccines such as MMR cause long-term health effects. On the other hand, we do know that people will become ill and some will die from the diseases this vaccine prevents. Measles outbreaks have recently occurred in the UK and Germany following an increase in the number of parents who chose not to have their children vaccinated with the MMR vaccine. Hence, discontinuing a vaccine program based on unproven theories would not be in anyone's best interest. 

Isolated reports about these vaccines causing long-term health problems may sound alarming at first. However, careful review of the scientific evidence reveals that these reports are isolated and not confirmed by scientifically sound research. Detailed medical reviews of health effects reported after administering vaccines have often shown these to be unrelated to vaccines, but rather have been related to other health factors. Because these vaccines are recommended widely to protect the health of the public, research on any serious hypotheses about their safety are important to pursue. Several studies are underway to investigate still unproven theories about vaccinations and severe side effects. 

In the meantime, it is important that your child receives the combined MMR and other childhood vaccines when these become due.

This article was adapted from:  http://www.cdc.gov/nip/vacsafe/concerns/autism/autism-mmr.htm