Tuesday, 18 January 2011

The MMR vaccine and the motivational powers of fear

Last week the scientific community once more denounced the work of Andrew Wakefield, the lead author of the now infamous Lancet paper which falsely linked the measles, mumps and rubella (MMR) vaccine to autism. Previous investigations into his work demonstrated unethical behaviour in his data collection; in the most distasteful example he was passing out £5 bills at a kids' birthday party in exchange for blood samples. There were also substantial and unreported conflicts of interest. While investigating the possible link between the MMR vaccine and autism he was paid as an expert witness by lawyers preparing a case against the manufacturers of the vaccine itself. If he had found no link, Dr. Wakefield wouldn't have been a particularly useful witness. Moreover, he had filed for patents for individual vaccinations. Individual vaccinations would have been an obvious choice if the triple vaccine was unsafe.

So we knew that Dr. Wakefield employed questionable practices and was motivated by questionable and undisclosed funding. He behaved unethically. But the more important question is, was he right? Is there a link between the MMR vaccine and autism?

Subsequent work from numerous labs has failed to reproduce his data. It is important to note that he was drawing his conclusions from a patient sample of 12. Statistical anomalies happen, especially with small sample sizes. A confidence interval of 95% is generally acceptable for the publication of an association between two medical conditions. This means that 95% of the time, the two conditions are associated. The converse is that 5% of the time the two medical observations are simply a coincidence. Theoretically, he could have observed the association and reported it, not knowing that he saw these conditions merely by chance. Was Dr. Wakefield the unfortunate victim of coincidence? Was his reputation sullied by fate?

Part of me had hoped that to be true. With great power comes great responsibility. Those in positions of authority, from politicians to medical professionals, have a great responsibility to promote the public interest. Dr Wakefield broke that trust. He fabricated data to fulfill his predictions. He was a liar. Of the twelve cases reported in his original paper, eleven of them were irreconcilable with the hospital's health records. The Lancet paper describes twelve children who were developmentally normal until they received the MMR vaccination, and then developed autism. According to the hospital records only one child actually had regressive autism, and five of them were developmentally abnormal before receiving the MMR jab. Dr. Wakefield was not the victim of coincidence, he was a fraud.

Why did his findings have such an enormous impact on public health, and how can the damage be repaired? Insurance companies can tell you the answer. Horrible but unlikely events are such stuff as nightmares are made on. It's terrifying to think that vaccinating your infant could cause him to become autistic, and correspondingly immunization rates in the UK fell below 80% in the early naughties. This has now caused another horrible and increasingly likely event; a fatal outbreak of measles, mumps or rubella. The fatality rate from measles for otherwise healthy people in developed countries is 3 deaths per thousand cases. In the last two years outbreaks of measles have occurred in Wales, New York, San Diego, France, and Germany. It is only a matter of time before an unvaccinated child dies from measles, and parents start rushing back to their GPs to have their children vaccinated. Fear is a powerful motivator.

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