MMR vaccine

   

The MMR vaccine is a combined vaccine for immunization against measles, mumps and rubella. It is generally administered to children around the age of 1 year, with a booster dose before starting school (i.e. age 4/5). It is widely used around the world; since its introduction in the 1970s, over 500 million doses have been used in over 60 countries. Those receiving the vaccine may experience a number of side-effects: 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. These effects are mild and temporary, vanishing within a few days. Children rarely have more serious reactions - only about one in every 100,000 vaccinations results in a severe allergic reaction. If treated quickly, the child should fully recover.


Epidemiology

Before the widespread use of a vaccine against measles, the incidence of measles was so high that in 2004, any patient over the age of 55 is assumed to have had had measles in the past. Today, because of vaccination, the incidence of measles in countries with routine childhood vaccination has fallen to less than 1% of people under the age of 30. Measles has a significant complication rate which includes pneumonitis and encephalitis.

Studies have shown that vaccination markedly reduces the mortality rate due to measles (CDC report on effect of vaccination against measles (http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5302a2.htm) in Africa between 1996-2002).

Mumps is another viral disease of childhood that used to be very common. A known but relatively rare complication of mumps is causing sterility in males.

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

All three diseases are highly contagious.

The MMR vaccine was designed to be a single-shot vaccine that protects against all three viral diseases. Significant improvements in reducing the incidence and therefore, the complications of the three diseases above has been attributed to widespread population vaccination with MMR.

Whilst there are known but rare side effects from using the MMR vaccine, in the public health perspective the overall benefit to the population is vastly in favour of continued vaccination.

The MMR controversy

Controversy has arisen because some scientists and parents claim that the vaccine may be linked to the development of a number of conditions, such as autism, bowel disorders such as Crohn's disease, and the brain disorder Creutzfeldt-Jakob disease (CJD).

During the 1980s and 1990s, a number of lawsuits were brought in the United States against manufacturers of vaccines, alleging that 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 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.

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 killed or seriously injured by the MMR vaccine. A pressure group called JABS (Justice, Awareness, Basic Support) was established to represent 800 families with children who were "vaccine-damaged."

In 1996, a controversy broke out in New Zealand concerning an allegation that the MMR vaccine could spread CJD. A Melbourne University academic claimed that MMR contained a human blood product, serum albumin, and could therefore spread CJD. The controversy died down after doctors highlighted the fact that serum albumin is not an ingredient of the MMR vaccine.

Dr. Andrew Wakefield's report

In February 1998, a group led by Dr. Andrew Wakefield published a paper, Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children (http://www.ncbugs.com/From_ncbugs/ACROBATS/Wakefield98.pdf) in the respected medical journal The Lancet. The report analysed the cases of twelve autistic children admitted to the Royal Free Hospital in north London in 1996-1997. The paper identified links between gastrointestinal disorders and developmental disorders in twelve children that were associated in time with environmental triggers. No conclusions or suggestions about causal links, such as that MMR could lead to autism, were made in the paper. However at a press conference following the paper's publication, Dr Wakefield responded verbally to a journalist's question by saying 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 that "I can't support the continued use of these three vaccines given in combination until this issue has been resolved."

The press conference sparked a major health scare and lurid headlines in the United Kingdom. The subsequent debate became polarised, Dr Wakefield's research was misused by parties from both sides of the argument and he became subject to many personal attacks, his critics savaging both the validity and the ethics of the research. The government and medical authorities such as the National Health Service (NHS) were eager to maintain confidence in the vaccine and stressed extensive epidmiological evidence that failed to show, any connection between MMR and developmental disorders. These assertions were disbelieved by many parents, not least because previous government pronouncements on safety had been widely discredited such as in the 'Mad Cow' (BSE) affair. It was also alleged that the government was 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 needed to avert epidemics of measles. Although an epidemic has not yet occurred, measles rates have increased and doctors have warned of the high likelihood of a future epidemic because of the failure of the protection offered by herd immunity.

A major factor in the controversy is that only the combined vaccine is available on 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 great majority of doctors prefer to administer the combined vaccine rather than the separate ones, as it is less distressing to the child and people are less likely to go through three vaccinations than one single one.

Great emphasis continues to be placed by major medical authorities around the world on the extensive epidemiolgical reasearch that, despite thousands of childeren being measured in numerous studies, no link between MMR and autism has been proven. Some critics such senior clinician John Walker Smith, although then a supporter of the triple vaccine, have pointed out that epidemiology is a 'blunt tool' and may miss causal relationships [1] (http://www.vaccinationnews.com/DailyNews/February2002/AutBowMeas.htm), for example it can be difficult to find two suitable populations of a sufficient size who which differ only in whether they have received the vaccination . Smith argued for more non-epidimological research to be conducted. Determining that there is no evidence for a link is not the same as proving that there is no link.

Dr. Wakefield left his job at the Royal Free Hospital in 2001. He now campaigns against the MMR vaccine on more or less a full time basis, travelling to the United States and Europe to lecture on the vaccine's alleged dangers.

In February 2004, it emerged that at the time that Dr. Wakefield had published his report, he was being paid £55 000 to assist lawyers seeking scientific evidence of a link between autism and the MMR vaccine. According to a Sunday Times investigation, several of the parents quoted as saying that MMR had damaged their children were also litigants. This was not revealed to either The Lancet or Dr. Wakefield's co-researchers. On February 20, The Lancet said that it should have never published Dr. 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. The General Medical Council, which is responsible for supervising medical ethics in the UK, has said that it is to investigate the affair. The investigation is likely to focus on whether Dr. Wakefield breached guidelines on the conduct of research, which include rules regarding potential conflicts of interest.

The investigation which led to some of the authors' withdrawing their support for the original paper was carried out by Brian Deer for The Sunday Times of London. http://briandeer.com/mmr-lancet.htm

In October 2004, the Journal of American Physicians and Surgeons published a report questioning the validity of one of the major epidemiological studies into MMR 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." [[2] (http://www.jpands.org/vol9no3/goldman.pdf)]

External links


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