Another media scare about MMR vaccine hits BritainBMJ 1999; 318 doi: http://dx.doi.org/10.1136/bmj.318.7198.1578 (Published 12 June 1999) Cite this as: BMJ 1999;318:1578
“Researchers deal new blow to vaccination” and “London study links children's vaccine to serious disease” proclaimed Britain's newspapers last week.
This latest media scare about the measles, mumps, and rubella (MMR) vaccine has left UK doctors fighting a rearguard action to try to minimise damage to vaccine uptake rates, already compromised by previous scares. The research on which the media reports were based linked paramyxovirus infection in childhood with subsequent inflammatory bowel disease (Gastroenterology 1999;116:796-803).
Scott Montgomery and colleagues from the Royal Free and University College Medical School in London analysed data from 7019 members of a nationally representative British cohort born in 1970. They identified subjects with inflammatory bowel disease and looked at the pattern of childhood infections recorded before the onset of the condition. They found that measles and mumps infections occurring together in the same year of life were significantly associated with ulcerative colitis and Crohn's disease, with odds ratios of 7.47 (95%confidence interval 2.42 to 23.06) and 4.27 (1.24 to 14.46) respectively, but not with insulin dependent diabetes mellitus, which they studied as a control disease. They concluded that atypical paramyxovirus infections in childhood may be risk factors for later development of inflammatory bowel disease.
Some sections of the UK media leapt on the new research with relish, making a link between the effects of the wild viral infections studied and the possible effects of attenuated viruses given in the MMR vaccine. London's Evening Standard, for example, said: “Though the children in the study were naturally exposed to infections before MMR existed, scientists are concerned that today's toddlers could suffer the same fate when they receive modified forms of the viruses through the jab.”
In the Gastroenterology paper, however, the researchers stated that they did not include monovalent measles vaccination as a potential confounding factor because “a significant relationship between vaccination alone and inflammatory bowel disease was not found in this cohort.” They did identify one cohort member with Crohn's disease who had had monovalent measles vaccination and wild mumps in the same year of life, but they admitted that “the number of cohort members with inflammatory bowel disease and this rare pattern of exposures is too small to draw a definite conclusion.”
Stretching the data
Commentators have been highly critical of the way in which the research was interpreted by the media, particularly in view of the likely impact on vaccination rates. The Department of Health commented: “There has been inaccurate reporting which is very irresponsible. None of the people in the study had had the MMR vaccine.” The chairman of the primary care virology group, Dr Nigel Higson, said: “It's crazy, because it is diseases and not vaccines being blamed in the study. I'm considering taking this to the Press Complaints Commission. We need to start making a stand against this, which is third hand reporting.”
The research itself has also been criticised. Dr Helen Bedford, research fellow at the Institute of Child Health in London, said: “The research relied on parents' memory of 10 years previously-it's difficult to be precise about something 10 years ago.”
Another study by the same researchers, published last year (Lancet 1998;351:637-41), was the subject of an inquiry by an expert panel from the Medical Research Council. In this study the researchers described a group of 12 children in whom they had identified a chronic enterocolitis that they thought might be related to neuropsychiatric dysfunction. They reported: “In most cases, onset of symptoms was after MMR immunisation. Further investigations are needed to examine this syndrome and its possible relation to this vaccine.”
The panel investigating this study concluded that there was no reason to change the policy on MMR vaccine and that no evidence indicated any link between MMR vaccination and bowel disease, or with autism. It said that the symptoms of an autism-like disorder generally appeared in the second year of life, when most children receive their MMR vaccination, but “such coincidence does not imply a causal link.”
The researchers are keen to emphasise that they have observed a possible connection between inflammatory bowel disease and atypical viral infection, rather than any link with the MMR vaccine. Dr Montgomery said: “I've been firefighting all week. Wild infections and vaccines are different entities, and this research neither confirms nor denies anything about the vaccine because it wasn't studied.” He pointed out that it is atypical infection—for example, multiple viral infections occurring close together—rather than vaccination that deserves further study, because it may have an association with inflammatory bowel disease.
In the meantime, Professor Arie Zuckerman, the principal and dean of the Royal Free and University College Medical School, has released a statement advising parents to carry on with MMR immunisations. This reflects the concern that the misinterpretation of the research by the media may reduce uptake of MMR vaccination, which is already falling. In England 92%of children received the MMR vaccine in 1996-7, but this fell to 88%by the October to December quarter of 1998. Although coverage is better in Scotland—92%of children there received it in the last quarter of 1998—the Scottish Centre for Infection and Environmental Health recently reported that some health boards have a continuing downward trend in uptake of the vaccine.
Deciding to vaccinate
Doctors are concerned that the reduced risk of infectious diseases in Britain has led people to focus on the risks of vaccination instead. Dr Higson is concerned that many parents have forgotten the disability that can be associated with rubella and the complications of measles. Analysing the problem, Dr Bedford suggested that parents worry because they feel that vaccination is something they are directly responsible for—unlike wild disease. She said: “Natural infection is somehow thought of as being out of our control, but immunisation is something parents have to decide to take up, so they feel more responsible.”
There is no doubt that the challenge of sustaining immun-isation rates in Britain grows harder with every scare. Norman Begg, consultant epidemiologist at the Public Health Laboratory Service, observed: “A lot depends on how the media react and look at the arguments, and hopefully it will be a five day wonder. But any one of these scares has the potential to catch fire, and I do get a sinking feeling about them.”