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The MMR vaccine is a mixture of live attenuated viruses, administered via injection for immunization against measles, mumps and rubella. It is generally administered to children around the age of one year, with a booster dose before starting school (i.e. age 4/5). It is widely used around the world; since introduction of its earliest versions in the 1970s, over 500 million doses have been used in over 60 countries. As with all vaccinations, long-term effects and efficacy are subject to continuing study. The vaccine is sold by e.g. Merck as M-M-R II^[1], GlaxoSmithKline Biologicals as Priorix, and sanofi pasteur as TRIMOVAX.

Contents 1 MMR immunization eliminated historical epidemics 2 Development, formulation and administration 3 Adverse effects 3.1 Urabe Mumps strain encephalitis 4 Retracted report claiming association with autism and bowel disease 5 References 6 See also

Before the widespread use of a vaccine against measles, its incidence was so high that patients born before 1949 are assumed to have had measles. Today the incidence of measles has fallen to less than one percent of people under the age of 30 in countries with routine childhood vaccination. Measles has a significant complication rate, which includes pneumonitis and encephalitis.

Studies, such as a Centers for Disease Control (CDC) report on the effect of vaccination against measles in Africa between 1996-2002, have shown that vaccination markedly reduces the mortality rate due to measles.^[2]

Mumps is another viral disease of childhood that was once very common. A known but relatively rare complication of mumps is sterility in males.

Rubella, otherwise known as German measles, was also very common before the advent of widespread vaccination. The major risk of rubella is if a pregnant woman is infected, her baby may contract congenital rubella from her, which can cause significant congenital defects.

All three diseases are highly contagious.

The MMR vaccine was introduced to induce immunity less painfully than three separate injections at the same time, sooner than at three separate encounters, and more efficiently than either. It also increases the likelihood of immunization against rubella in populations for which it has no meaningful use (all those other than pregnant women) given the costs, inconvenience and possible side-effects of vaccination, including arthritis and encephalitis^[3]. The incidence and therefore the complications of the three diseases above have declined significantly and this is generally attributed to widespread population vaccination.

The component viral strains of MMR vaccine were developed by propagation in animal cells. The live viruses require animal cells as a host for production of more virus.

For example, in the case of mumps and measles viruses, the virus strains were grown in embryonated hens' eggs and chick embryo cell cultures. This produced strains of virus which were adapted for the hens egg and less well-suited for human cells. These strains are therefore called attenuated strains. They are sometimes referred to as neuroattenuated because these strains are less virulent to human neurons than the wild strains.^{[4] [5]}

Disease Immunized	Component Vaccine	Virus Strain	Propagation Medium	Growth Medium
Measles	Attenuvax	Enders' attenuated Edmonston strain [6]	chick embryo cell culture	Medium 199
Mumps	Mumpsvax[7]	Jeryl Lynn (B level) strain[8]
Rubella	Meruvax II	Wistar RA 27/3 strain of live attenuated rubella virus	WI-38 human diploid lung fibroblasts	MEM (solution containing buffered salts, fetal bovine serum, human serum albumin and neomycin, etc.)

The virus is extracted from the human albumin growth medium via the Cohn cold ethanol fractionation method. ^[1]

MMR II is supplied freeze-dried (lyophilized) and contains live viruses. Before injection it is reconstituted with the solvent provided. It is administered by a subcutaneous injection.

There are a number of adverse effects listed in the product documentation for the MMR vaccine.^[1] Additional side effects and variants are reported including: a rash or slight fever for a few days, one to two weeks after receiving the vaccine, occasionally accompanied by a mild swelling of the salivary glands and some aching or swelling of the joints, respectively from the measles, mumps and rubella components, which have differing incubation periods. They are usually mild and temporary, vanishing within a few days. There are rare reports of more serious adverse effects — only about one in every 100,000 vaccinations is reported to have resulted in a severe adverse effect such as encephalitis or meningitis. Acute disseminated encephalomyelitis is a rare severe adverse effect of the vaccine.^[9]

The medical community does recognize that effects, rarely serious, may occur from each component of the MMR vaccine. However, the consensus of medical opinion is that the vaccine is very safe. In the opinion of most public health authorities, the benefit to the population outweighs these concerns.^[10][11][12]

Parents may choose to have each of the three components given separately, but the overwhelming medical opinion is that such spacing of injections does not reduce the chance of adverse effects, but increases the opportunity for infection by the two diseases not immunized against first^[13].

Prior to use of Jeryl-Lynn strain Mumps Vaccine in MMR-II, Urabe Mumps strain was used.^{[citation needed]}

Britain's Telegraph newspaper reported on-line in March, 2007 on revelations from an FOIA request that the Urabe MMR vaccine in Britain was linked to cases of encephalitis which caused brain damage. And despite that America had already reported "adverse reactions" to MMR containing Urabe Mumps strain, the Thatcher government went ahead with the mass vaccinations. ^[14]

Main article: The MMR controversy

In the UK, the vaccine was the subject of controversy despite the 1998 paper by Andrew Wakefield et al reporting a study of 12 children who had autism and bowel disease with onset after MMR^[15] concluding that there was no proof of "an association between MMR vaccine and the syndrome described".^[16] Numerous peer-reviewed studies have also since failed to show any correlation.

Wakefield nevertheless suggested during a 1998 press conference that giving children the vaccines in three separate doses would be safer than a single jab. This suggestion was again not supported by the paper, his 12 co-authors nor by any scientific evidence^[15] and has been heavily criticized, both on scientific grounds and for triggering a decline in vaccination rates.^[17] In fact, it is widely believed that using separate, single vaccines in place of MMR puts children at increased risk since the combined vaccine reduces the risk of them catching the diseases while they are waiting for full immunisation cover.^[16][18]

In 2001, Berelowitz, one of the co-authors of the paper, said "I am certainly not aware of any convincing evidence for the hypothesis of a link between MMR and autism".^[16] Subsequently, in 2004, the intepretation section of the study was formally retracted by ten of Wakefield's twelve co-authors, including Berelowitz.^[19]The retraction followed an investigation by The Sunday Times ^[20]

The Urabe Mumps strain was not used in Britain after 1992, six years before the Wakefield report. ^[14]

1. ^ ^{a b c} Merck Co. (1990, 1999). "M-M-R II (Measles, Mumps, and Rubella Virus Vaccine Live)". Merck Co..
2. ^ http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5302a2.htm
3. ^ http://www.immunizationinfo.org/vaccineInfo/vaccine_detail.cfv?id=24#sideeffects
4. ^ Immunization, Vaccines and Biologicals. World Health Organization (2003).
5. ^ "Changes in Mumps Virus Gene Sequence Associated with Variability in Neurovirulent Phenotype". 
6. ^ Attenuvax Product Sheet (PDF) 1. Merck & Co (September 2002). Retrieved on July 7, 2006.
7. ^ Merck Co. (1990, 1999). MUMPSVAX (Mumps Virus Vaccine Live) Jeryl Lynn™ Strain. Merck Co..
8. ^ Young ML, Dickstein B, Weibel RE, Stokes J Jr, Buynak EB, Hilleman MR. (1967). "Experiences with Jeryl Lynn strain live attenuated mumps virus vaccine in a pediatric outpatient clinic". Pediatrics. PubMed. 
9. ^ http://www.ktl.fi/portal/suomi/julkaisut/kansanterveyslehti/lehdet_2003/5-6_2003/rokotteiden_haittavaikutukset_vuonna_2002/
10. ^ Stop witch-hunting Wakefield. Spiked Online (2006).
11. ^ [1] Horton, The Lancet Volume 363, Number 9411, 06 March 2004 "... the large measure of consensus that MMR is safe".
12. ^ U.K. National Health Service official MMR information
13. ^ http://www.mmrthefacts.nhs.uk/basics/truths.php
14. ^ ^{a b} Mark Watts (telegraph.co.uk). "Early fears about MMR in secret papers".
15. ^ ^{a b} MMR - the controversy. Retrieved on 19 March 2007.
16. ^ ^{a b c} MMR: myths and truths. Retrieved on 19 March 2007.
17. ^ BBC News, Doctors issue plea over MMR jab. Retrieved on 26 June 2006.
18. ^ MMR - scientific research. Retrieved on 29 March 2007.
19. ^ Murch SH, Anthony A, Casson DH, Malik M, Berelowitz M, Dhillon AP, Thomson MA, Valentine A, Davies SE, Walker-Smith JA (6 March 2004). "Retraction of an interpretation". The Lancet 363(9411). PMID 15016483. 
20. ^ The MMR-autism scare - our story so far. Retrieved on 3 April 2007.

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