Vaccination is one of the greatest public health interventions of the twentieth century. Since 1963, data shows a clear drop in global death rates from the diseases that they have been designed to prevent. In fact, before the vaccine, global deaths were estimated at 2.6 million a year. And after, less than 100,000. And this is just one vaccine. But now measles rates are rising. The reason? Some don’t trust vaccines and won’t use them. And this is forgivable, there is a lot of misinformation out there. So lets have a look at the common issues and explain why the myths just aren’t facts. Today; ‘Vaccines cause Autism.’
Vaccination and Good Science.
But before we go on, lets explain in simple terms how a good study works. You build a hypothesis ‘I.e Bananas cause cancer’. You then design an experiment to test this idea. Your ‘independent variable‘ is ‘banana eating’ (Yes or No,) and your ‘dependent variable‘ is ‘cancer diagnosis’ (Yes or No.)
Unfortunately, we know that many things cause cancer, and that patients may be exposed to one or more of these causes at once. So how do you adjust for this? One way is to create a ‘test’ and ‘control’ group, where you have one group exposed to the ‘independent variable’ and one not, then see the outcomes.
You then run statistical analysis to compensate for error, and make a judgement. At this point you can either reject the null hypothesis (i.e, bananas don’t cause cancer,) or you can accept the null. This ‘finding’ is then compared with other research before any hard conclusions are drawn (corroboration.)
It seems pretty straight forward. Scientists use other tricks such as ‘double blinding‘ (making it so neither the patient nor researcher knows which patient is in which group,) and the use of ‘placebo‘ to ensure the patient is also unsure. This reduces the risk of bias. For example if the Scientist wanted to prove that ‘bananas cause cancer’, he or she could simply place all the patients who smoke in the ‘banana’ group, and then claim that the bananas caused lung cancer. Furthermore, a patient who smokes may not wish to develop cancer, so they lie and say they don’t eat bananas. The data is not trustworthy.
Not sure how you could create a placebo banana though.
Finally, (but not exhaustively.) the researcher must use a large study size and wide range of patients to compensate for artifactual variation. i.e, atypical cases have a greater influence on statistics when a group is small. For a study examining links between Vaccination and disease, using the same parameters are important. It must then be compared with all the evidence generated by other studies.
This is where the myth falls down.
Wakefield, Vaccination , Autism And Bad Science
In 1988 Dr. Andrew Wakefield published a small study where his team compared rates of Autism (amongst other medical issues,) with MMR Vaccination. In the twelve children that he reviewed, 9 were ‘found’ to have ”Autism.” As a result, the media went wild declaring that Vaccines cause Autism. Over the intervening years, Wakefield was struck from the medical register, the paper itself retracted and the man himself either vilified or worshipped. But why?
The simple answer is that the study itself was flawed. There are multiple reasons, but we will focus on the most powerful.
Firstly, all of Wakefields patients had both the MMR and displayed symptoms suggestive of Autism. The diagnosis itself was not clear, and the method of data gathering used inaccurate. So he was already on shaky grounds. By reviewing only MMR patients, he provided no comparison group by which he could assess this independent variable.
He also relied on unclear diagnoses, and ignored confounding variables that would have undermined his conclusions. As all his patients ‘had autism’, you could not claim that one intervention had caused it. This, by itself, is enough to debunk the study. But it doesn’t stop there.
Bias and Fake Data
The next issue is bias. Wakefield failed to disclose that he had received $55,000 dollars to launch the study. Now all studies require money, but is unusual to not show where it came from. And when a study publishes a result with political and financial implications, it is obvious why journals demand information on funding. A company could easily bribe a scientist to formulate a study showing their product is better than another. This happens, but is usually caught early before the public is misled.
Wakefield has been accused of a conflict of interest, where he would have benefited from ‘finding a link.’ It is worth noting that his funders were alleged lawyers seeking to prove the hypothesis, and the patients potential claimants. Wakefield himself has been reported to have received hundreds of thousands of dollars from the lawyers in question. You can see how the study is beginning to look a little concerning.
Finally, Wakefield seemed to have manipulated the data to support his hypothesis. This invalidates the study.
So all in all, we have a small study, with no comparison group, no recognition of conflicting variables, potentially paid for by those with vested interests, with manipulated data. It is a small wonder that people still trust the study.
Vaccinations and The Scientific Concensus
Within Science it is important to compare the findings of any study with all the others relevant. This is called corroboration. Scientific consensus is build upon ‘argument from plausibility’, that is ‘what is most likely true by the evidence available.’ So it stands to reason that any new study, especially if it raises new avenues or odd conclusions, should be compared with what is already out there.
A new study may directly refute all the work done before, and it could be correct in doing so. It could also just be a bad study. Without rigorous work to find out which, we just wouldn’t know. Unfortunately for Wakefield and the purveyors of his myth, the science consensus against his conclusions is very strong.
A 2014 metaanalysis reviewed over 10 studies including over 1 million children, each with better experimental design. The analysis conclude very simply ‘vaccinations are not associated with the development of autism or autism spectrum disorder.’ Put very clearly, Wakefield’s data was bogus, his methods suspect, intent risible and contrasting evidence base overwhelming. But unfortunately, he had an effect. After publication vaccine rates fell, and his myth is still used today by advocates against vaccination.
So next time someone tells you ‘vaccines cause autism’ you can simply say;
”Wakefield’s study was prone to inaccuracy, manipulation, pay outs and is no longer accepted. Numerous studies have shown no link, and these can be verified as both methodologically sound ethically amiable. What is more likely? That Wakefield’s study has exposed something that numerous large studies have missed, or that Wakefield himself faked it for personal gain?’
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The opinions in this article are those of Dr Janaway alone and do not necessarily represent those of his affiliates. Dr Janaway is an advocate of safe vaccine use. If you have health concerns, please see your local health care provider. Image courtesy of CDC Global (Flickr.)