MMR vaccine

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The MMR vaccine is a mixture of live but 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.

A number of adverse effects 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 reactions — only about one in every 100,000 vaccinations is reported to have resulted in a severe allergic reaction.

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Epidemiology

Image:Measles incidence-cdc.gif 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.[1]

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. Image:Rubella-us-1966-93-cdc.gif

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. The incidence and therefore the complications of the three diseases above have declined significantly and this is generally attributed to widespread population vaccination.

While there are known effects, rarely serious, from each component of the MMR vaccine, from a public health perspective, the benefit to the population outweighs these concerns. Most people are in favour of continued vaccination programs.

A concerned individual may choose any one of the 3 components of the MMR vaccine separately, and it has been asserted that contrary to general medical opinion spacing out these immunizations individually may decrease the chance of adverse effects. By increasing the time until immunised, spacing the components inevitably increases opportunities for infection with at least two of the diseases for the individual and their contacts.

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The MMR controversy

(also see: Vaccine controversy)

Controversy has arisen regarding the safety of the MMR vaccine, because a few scientists and parents argue that the vaccine is the cause of the increased incidence of autism noted in western countries and Japan, and bowel disorders such as Crohn's disease. A theory advanced by proponents of the link is that the MMR vaccine overwhelms an immune system they assert is already struggling from the effect of thimerosal contained in previous vaccines. They assert that live measles virus in the formulation of the MMR is detrimental to susceptible individuals in a fashion in which wild measles never was. Proponents point to studies showing live measles virus is detected in the gut of these individuals.Template:Fact

During the 1980s and 1990s, a number of lawsuits were brought in the United States against manufacturers of vaccines, alleging the vaccines had caused a variety of physical and mental disorders in children. While these were inconclusive, they did lead to a massive jump in the costs of the MMR vaccine, as pharmaceutical companies sought to cover potential liabilities by lobbying for legislative protection. By 1993, Merck KGaA had become the only company willing to sell MMR vaccines in the United States and the United Kingdom. Two other MMR vaccines were withdrawn in the UK in 1992 on safety grounds arising from the strain of mumps component.

In September 1995, the Legal Aid Board in the UK granted a number of families financial assistance to pursue legal claims against the state health authorities and the vaccine's manufacturers, claiming that their children were killedTemplate:Fact or seriously injured by the MMR vaccine. A pressure group called JABS (Justice, Awareness, Basic Support) was established to represent families with children who, their parents said, were "vaccine-damaged."

In 1996, in New Zealand claims by an academic from Melbourne University that MMR contained a human blood product, serum albumin, and could therefore spread CJD spread anxiety. This did not last, since serum albumin was demonstrably not an ingredient of the MMR vaccine.

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Dr. Andrew Wakefield's report

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1998 Lancet paper

In February 1998, a group led by Dr. Andrew Wakefield published a paper (which later was subject to a qualified retraction by co-authors; see below), Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children in the respected medical journal The Lancet. The report analysed the cases of twelve children with developmental disorders admitted to the Royal Free Hospital in north London in 1996-1997, described a collection of bowel symptoms, which Wakefield asserted was evidence of a possible novel syndrome, which he would later call autistic enterocolitis, and recommended further study into the possible link between the condition and environmental triggers, i.e., the MMR vaccine. The paper proposed links between gastrointestinal symptoms and developmental disorders in twelve children that were alleged to be associated in time with MMR vaccination. No conclusions about causal links, such as that MMR could lead to autism, were reached. However, at a press conference before the paper's publication, Dr Wakefield said that he thought it prudent to use single vaccines instead of the MMR triple vaccine until this could be ruled out as an environmental trigger, given that parents of eight of the twelve children studied were said to have blamed the MMR vaccine, saying that symptoms of autism had set in within days of vaccination at approximately 14 months. He declared, "I can't support the continued use of these three vaccines given in combination until this issue has been resolved." In a video news release, issued by the hospital to broadcasters in advance of the press conference, he called for MMR to be "suspended in favour of the single vaccines." [2]

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Controversy following publication of report

The paper, press conference and video sparked a major health scare in the United Kingdom. The subsequent debate became polarised. Wakefield's research was misused by parties from both sides of the argument. The controversy was seized upon by some UK newspapers, which argued that separate vaccines ought to be available on the NHS. It can be argued that these newspapers may have been serving their own interest by promoting this "health scare story" up the news agenda. He became subject to attacks, his critics questioning the validity and the ethics of the research. The UK government and medical authorities, such as the National Health Service (NHS), stressed extensive epidemiological evidence that failed to show any connection between MMR and developmental disorders. These denials were disbelieved by some parents, not least because previous government pronouncements on safety had been faulty, such as in the 'Mad Cow' (BSE) affair. The government was also alleged to be unwilling to support the use of separate vaccines because the NHS could not afford them. As a result, the takeup of MMR dropped sharply, from 92% in 1996 to 84% in 2002. In some parts of London, it was said to be as low as 60% - far below the rate thought to be needed to avoid an epidemic of measles. Although an epidemic has not yet occurred, measles rates have risen and doctors have warned of the likelihood of a future epidemic, because of the failure of the protection offered by herd immunity.

A factor in the controversy is that only the combined vaccine is available through the UK National Health Service; those who do not wish to have it given to their children must either have the separate vaccines given privately, or not vaccinate their children at all. The Prime Minister, Tony Blair, has refused to state whether his son Leo has received the MMR vaccine, but has strongly supported the vaccine in public. The Chancellor, Gordon Brown, has confirmed his son has been immunised[3].

The great majority of doctors prefer to administer the combined vaccine rather than the separate ones, as it is less distressing to the child, and parents are more likely to attend for one vaccination than for three.

Epidemiologic research on hundreds of thousands of children in numerous studies continues to show no link between MMR and autism. Critics of these epidemiology studies, such as retired British clinician John Walker-Smith, although a supporter of the triple vaccine, have pointed out that epidemiology is a 'blunt tool' and may miss causal relationships. [4] For example, it can be difficult to find two populations of sufficient size which differ only in whether they were vaccinated.

Dr. Wakefield left his job at the Royal Free Hospital in 2001. His continued research includes involvement in scientific collaborations in the U.S and Europe, and a report on possible immunologic, metabolic, and pathologic changes occurring in what Wakefield has called "autistic enterocolitis", links between intestinal disease and neurologic disorders in children, and the potential relationship of these disorders to environmental causes, such as vaccines. [5]

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Conflict of interest allegations

In February 2004, it emerged that when Wakefield had published The Lancet report, £55,000 funding was received by the Royal Free Hospital from lawyers seeking evidence of any link between autism and the MMR vaccine [6]. According to a Sunday Times investigation, several of the parents quoted as saying that MMR had damaged their children were also litigants. Although Wakefield maintains the funding was properly disclosed from the outset, allegations have been made that the funding was not revealed to either The Lancet or Wakefield's co-researchers. On February 20, 2005, The Lancet said it should have never published Wakefield's study, which was "flawed" because Dr Wakefield had "a fatal conflict of interest." Several of Dr. Wakefield's co-researchers also strongly criticised the lack of disclosure. [7] The General Medical Council, which is responsible for licensing doctors and Supervising Medical Ethics in the UK is reported to be investigating the affair. [8].

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Retraction of Lancet paper

The investigation which led to 10 of the 13 authors' of the 1998 Lancet paper formally retracting the claim of having found a possible link between MMR and autism was carried out by Brian Deer for The Sunday Times of London. [9] Deer continued his investigation in a British television documentary, MMR: What They Didn't Tell You, broadcast on November 18 2004. This alleged that Wakefield had applied for patents on a rival vaccine to MMR, and knew of test results from his own laboratory at the Royal Free hospital that contradicted his claims. [10]

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Recent studies

Epidemiological research continues to show a dramatic increase in the incidence of autism, but whether the increase is real, rather than an artifact of diagnosis and reporting, is unknown, and no causal connection has been demonstrated to the MMR vaccine. Since Wakefield's paper, there has been substantial clinical research investigating his claim to have found measles virus located in the gut of proportion of children, much of which has been financed by litigation, with the results not reported on legal grounds.

  • In October 2004, the Journal of American Physicians and Surgeons, formerly the Medical Sentinel, magazine of the conservative Association of American Physicians and Surgeons, published a paper by Wakefield supporters and concluded that "Developing safer vaccination strategies and supporting further investigation of the hypothesized link between the MMR vaccine and autism should have a high priority." It also noted that in Denmark Thimerosal is eliminated as a factor in any relationship between MMR and autism. [11]
  • In October 2004 a review, financed by the European Union, was published in the October 2004 edition of Vaccine<ref>Template:Cite journal</ref> that assessed the evidence given in 120 other studies and considered unintended effects of the MMR vaccine. The authors concluded that
    • the vaccine is associated with some positive and negative side effects,
    • it was 'unlikely' that there was a connection between MMR and autism, and
    • 'The design and reporting of safety outcomes in MMR vaccine studies ... are largely inadequate'.
  • In January 2005, intensive research in a single county in Minnesota reported an eightfold increase in the incidence of autism over a period beginning in the early eighties and ending in the late nineties but found no evidence of a link with MMR. The authors of the research suggested that the increase in autism was due to an increased awareness of the disorder, a growth in services, and changing definitions. [12]
  • Japan provided a natural experiment, combined MMR vaccine was introduced in 1989, but the programme was terminated in 1993 and only single vaccines used thereafter[13]. In March 2005 a study of over 30,000 children (278 cases) born in one district of Yokohama concluded "The incidence of all autistic spectrum disorders, and of autism, continued to rise after MMR vaccine was discontinued. The incidence of autism was higher in children born after 1992 who were not vaccinated with MMR than in children born before 1992 who were vaccinated. The incidence of autism associated with regression was the same during the use of MMR and after it was discontinued." Autism rose (from 46-86 cases per 10,000 children, to 97-161/10,000). The authors' concluded: "The significance of this finding is that MMR vaccination is most unlikely to be a main cause of ASD, that it cannot explain the rise over time in the incidence of ASD, and that withdrawal of MMR in countries where it is still being used cannot be expected to lead to a reduction in the incidence of ASD."<ref>Template:Cite journal|volume=46|issue=6|title=No effect of MMR withdrawal on the incidence of autism: a total population study|pages=572|date=June 2005|author=Hideo Honda, Yasuo Shimizu and Michael Rutter}} Cited in New Scientist[14], reviewed in Bandolier with graph of main results.</ref> It should be noted that this study did not question whether or not both MMR and separate vaccines were capable of contributing to ASD, Crohns and other disorders, with separate vaccines, rather than MMR, being responsible for a more severe effect.

Dr. Wakefield contends the pattern of autism rates revealed by the data support his hypothesis[15] . His views, however, have found little support<ref>Template:Cite news</ref>.

  • In October 2005, the Cochrane Library published a review of 31 scientific studies, and concluded that "there was no credible evidence behind claims of harm from the MMR vaccination" and "MMR is an important vaccine that has prevented diseases that still carry a heavy burden of death .... ". [16] However the authors of the report stated that "The design and reporting of safety outcomes in MMR vaccine studies, both pre- and post-marketing, are largely inadequate."<ref>Template:Cite journal|title=Vaccines for measles, mumps and rubella in children|author=

V Demicheli, T Jefferson, A Rivetti, D Price|journal=The Cochrane Database of Systematic Reviews|year=2005|issue=4}}</ref> Cochrane, based in Oxford, England, is widely regarded by scientists as the most authoritative independent reviewer of medical literature, and the custodian of "evidence-based medicine".

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References

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External links

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