The MMR vaccine is recommended by the NHS to protect children against measles, mumps and rubella. The NHS and medical authorities believe that it offers your child the safest and most effective protection. However, some doctors are concerned that the vaccine may cause problems in a small minority of children.

Written by Dr Richard Halvorsen.

What is the MMR vaccine?

MMR is a 3-in-1 vaccine that protects against measles, mumps and rubella (German measles).

When was the MMR vaccine introduced?

The vaccine was introduced into the UK in 1988 with, some have argued, inadequate safety trials. Initially children received only one MMR vaccine – at 13-15 months – but a second dose was added in 1996, because the vaccine was less effective than at first hoped. Two of the initial three MMR vaccines used in the UK were withdrawn in 1992 because they were causing some children to be hospitalised with ‘aseptic meningitis.’ There are currently two MMR vaccines licensed for use in the UK: Priorix, made by GlaxoSmithKline, and M-M-R-VaxPro, made by Sanofi Pasteur MSD. The vaccines contain different strains of measles and mumps vaccine, but are very similar in terms of safety and effectiveness.

When is the MMR vaccine given?

The MMR vaccine is given as part of the NHS schedule at 13 months, and again at 3 to 4 years of age. The second vaccine is not strictly a ‘booster’, in that it is not necessary if all three parts of the first MMR worked; it is, rather, a second chance to be protected in case one or more parts failed to work first time round. The MMR contains three live viruses that have been ‘attenuated’ or made safe. The vaccine is used in most wealthy countries in the world apart from Japan.

How well does the vaccine work?

Only one dose of the vaccine is needed to provide protection, but, like all vaccines, it does not work in everyone. The effectiveness of the vaccine varies between its different components: both the measles and rubella parts are effective, protecting at least 9 out of every 10 children immunised, whereas as the mumps part is rather less effective, protecting two children out of very three vaccinated. After two doses of the vaccine, nearly all children are protected against measles and rubella, and around eight out of every nine children against mumps. It is not known how long the vaccines last, but most children will remain protected well into adulthood.

How safe is it? Can the vaccine cause autism?

Fears were aroused that it might be causing autism and bowel disease in some children following the publication of a paper in 1998 (i). At the sane time Dr Andrew Wakefield, one of the paper’s authors, recommended giving the three single vaccines separately, instead of the triple MMR. This was a controversial suggestion that has been strongly rejected by the government and medical establishment. Though most parents continued to give their children the MMR vaccine, many shunned the vaccine, with some paying to obtain the single vaccines privately.

At around the time of the introduction of the MMR, the number of cases of autism being diagnosed started to increase dramatically, and some feared that the MMR might have triggered this rise. Experts debated whether the rise was even real, or whether it is due to increased recognition and diagnosis of autism. Most experts now agree that the large rise has been caused partly by increased diagnosis, but also by a real increase in the number of children with autism.

Research, including large population studies, has since shown that the MMR is not causing the large majority of autism, but has failed to exclude the possibility that it is causing autism in a small number of susceptible children. (ii,iii,iv,v)

The vaccine strain measles virus has been found in the guts - and brains – of some autistic children; though this research is controversial, it does support many parents’ beliefs that the MMR vaccine has caused their children to become autistic. (vi,vii)

The government, and most doctors, have strongly defended the safety of the vaccine, but a question mark remains over whether it may not be safe in a small minority of children.

Are there any other side-effects?

One in 6 children will develop a fever, usually around 7-10 days after immunisation; in one in 20 the fever will be high (over 39.5 C). (viii) Around this time 1 in 750 will suffer a febrile convulsion (a fit as a result of a fever); though alarming, these rarely have any long-term consequences. (ix)

One child in 11 will have diarrhoea after receiving the vaccine, and the same number a rash.

The vaccine causes a first attack of Idiopathic Thrombocytopaenic Purpura (ITP) in 1 in 25,000 children receiving the vaccine. This is a rare immune related bleeding disorder, from which most children make a full recovery. (x)

Receiving the MMR vaccine may increase the risk of asthma and eczema.

The vaccine can cause encephalitis, an infection of the brain that can be fatal, but this is extremely rare. However, the vaccine is safe and effective in the large majority of children.

Dr Richard Halvorsen

Dr Richard Halvorsen is a GP with over 20 years experience who has a special interest in children’s immunisation. His book, The Truth about Vaccines was published in 2007. He runs Babyjabs, a dedicated children’s immunisaiton service that offers parents a choice of single and small combination vaccines, as alternatives to both the baby vaccines and the MMR.

Useful links

www.immunisation.nhs.uk/Vaccines/MMR (MMR information on the NHS web site)

www.babyjabs.co.uk (Babyjabs, a dedicated children’s immunisaiton service offering a choice of single and small combination vaccines)

www.jabs.org.uk (support group for vaccine damaged children)

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i Wakefield AJ et al. Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children. The Lancet 1998; 351:637-41

ii Madsen KM et al. A population-based study of measles, mumps and rubella vaccination and autism. The New England Journal of Medicine 2002; 347: 1477-1482

iii Kaye JA et al. Mumps, measles, and rubella vaccine and the incidence of autism recorded by general practitioners: a time trend analysis. British Medical Journal 2001; 322: 460-463

iv Davis RL et al. Measles-Mumps-Rubella and Other Measles-Containing Vaccines do not increase the risk for Inflammatory Bowel Disease. A Case-control Study from the Vaccine Safety Datalink Project. Archives of Pediatric and Adolescent Medicine 2001; 155: 354-359.

v Smeeth L. Cook C. Fombonne E. Heavey L. Rodrigues LC. Smith PG. Hall AJ. MMR vaccination and pervasive developmental disorders: a case-control study. Lancet 2004; 364(9438): 963-9.

vi Uhlmann V, Martin CM et al. Potential viral pathogenic mechanism for a new variant inflammatory bowel disease. Molecular Pathology 2002; 55: 84-90

vii Bradstreet JJ et al. Detection of Measles Virus Genome RNA in Cerebrospinal Fluid of Children with Regressive Autism: a Report of Three Cases. Journal of American Physicians and Surgeons 2004; 9: 38-45

viii LeBaron CW, Bi D, Sullivan BJ, Beck C, Gargiullo P. Evaluation of Potentially Common Adverse Events Associated With the First and Second Doses of Measles-Mumps-Rubella Vaccine. Pediatrics 2006; 118 (4): 1422-1430.

ix Vestergaard M et al. MMR Vaccination and Febrile Seizures. Evaluation of Susceptible Subgroups and Long-term Prognosis. Journal of the American Medical Association 2004; 292: 351-357

x Jonville-Bera AP et al. Thrombocytopenic purpura after measles, mumps and rubella vaccination: a retrospective survey by the French regional pharmacovigilance centres and pasteur-merieux serums et vaccines. Pediatric Infectious Disease Journal 1996; 15: 44-8