The Pharmaceutical Journal
Vol 269 No 7224 p703
16 November 2002

This article
Reprint
Photocopy

News summary

Related websites
New England Journal of Medicine abstract (more)
The Lancet (www.thelancet.com)

Latest MMR study supports vaccine safety but methodology is questioned

Measles, mumps and rubella (MMR) vaccine does not increase the risk of autism or autistic-spectrum disorder, according to the results of a population-based study. However, an independent reviewer has questioned the methodology used by the researchers.

In the study, Danish researchers calculated that the relative risk of autism in vaccinated children compared with unvaccinated children was 0.92 (95 per cent confidence interval 0.68–1.24), while the relative risk of another autistic-spectrum disorder was 0.83 (0.65–1.07) (New England Journal of Medicine 2002;347:1477).

This study adds to a growing bank of published research investigating the safety of the MMR vaccine since gastroenterologist Dr Andrew Wakefield first suggested it could be involved in the development of inflammatory bowel disease and autism four years ago (Lancet 1998;351:637).

However, Dr Tom Jefferson, who is a co-ordinator for the Cochrane vaccine field and has carried out an independent review of MMR research, says the vast majority of the studies are flawed. "The first criticism was that no one had evaluated the evidence methodologically. The reporting left a lot to be desired — methodologically the studies were very weak and sound information was only available from two of the trials," he said. Dr Jefferson also questioned the methodology of the latest Danish study: "They call it a cohort study — I would not agree. In the statistical methods section there is a clear reference to the fact that the [vaccinated and unvaccinated] children are the same. They followed the cases up before MMR and then after MMR exposure. I am not sure about the conclusions of this study," he added.

The researchers examined the medical records of over 537,000 children born between 1991 and 1998, 82 per cent of whom they said had received MMR vaccine. They found that development of autistic disorder was unrelated to age at vaccination, time since vaccination or date of vaccination (P=0.23, 0.42 and 0.06, respectively), and say the results provide three strong arguments against a causal relationship between the MMR vaccine and autism. First, the risk of autism was similar in vaccinated and unvaccinated children, secondly, there was no temporal clustering of cases of autism at any time after vaccination and, thirdly, neither autism nor autistic-spectrum disorder were associated with MMR vaccination. They also rule out the possibility of a subgroup of vulnerable children: "... the fact that the overall relative risk of autism or an autistic-spectrum disorder was less than 1.0 does not support [this]."

Dr Jefferson commented: "I do not think there is any evidence for an association but that is not the point. People should be able to go somewhere to look at an independent analysis of the research. The Department of Health website is not independent. If pharmacists have an independent role in advising the public then maybe they are the people to do it. I feel sorry for health care workers — what advice do they rely on?"

Dr Jefferson is hoping to secure independent funding for a website aimed at parents and scientists, where Cochrane reviews on the safety of vaccines and criticism on individual studies could be published.