Lucky (or sometimes unlucky) numbers

We all love stats, don’t we? Okay, fair enough, most people, and especially students, hate stats. But, despite this apparent hatred, we all like to pepper our arguments with stats that seem to offer the definitive proof that we are right. Let’s face it, objectively, we are unlikely to make great use of stats that prove us wrong. So, it strikes me that social scientists, of which I count myself, should try to demystify stats and what we can do with them.
There is a website which I am particularly fond of called Getstats which aims to foster a better understanding of statistics. So I was disappointed with a recent article on measles which seemed to lambast parents who failed to present their children for the MMR jab. According to the piece:
“Some people put more credence in anti-science commentators more interested in sensation than public enlightenment than they did in their own GPs or in trusted websites such as NHS Choices.”
Whilst the author is careful not to blame Andrew Wakefield personally for the decline in uptake of MMR, it does makes the extraordinary claim that measles: “had been on its way out – thanks to the success of the MMR vaccine…”
According to the NHS Choices website, MMR is the reason for the decline in cases of measles, but nowhere, as far as I can tell, does it say that MMR is completely safe. Indeed, the advice suggests that there can be side effects. It does claim, as do Getstats that the link between MMR and autism has been disproved, and that may well prove to be the case.
It is certainly disputable whether the fall in the death rate from measles can be attributed to MMR. Figures from the Office for National Statistics show that the death rate from measles had been falling since 1901. The trend was uniform throughout the 20th Century and shows no sudden dip in the years following 1988, when the MMR jab was first introduced. Deaths from measles since the 1950’s have been rare and have been steadily declining.
When my son was 2 years old, and due his MMR jab, we read as much literature on MMR as we could find including the Lancet article by Andrew Wakefield which has been at the centre of the controversy, and which has since been removed from public circulation. (Though you can read it here.) Relying on my own “scientific” knowledge and understanding of statistics the more I read, the more confused I became. Assurances by a GP, who was being paid a bonus to increase the numbers vaccinated, did not strike me as sincere, especially since that GP was unable to answer most of my questions about the validity of claims that the vaccine was entirely safe. My understanding of the Wakefield article was that it never said that there was a direct link between MMR and autism. What they suggested needed further research was the relationship between a specific bowel complaint, autism and MMR. To cite the article: “We did not prove an association between measles, mumps and rubella vaccine and the syndrome described.” What happened was that some parents of autistic children claimed that the onset coincided with the MMR jab. And, then the media became excited and so did the Government. What should have been a decision based on weighing up the relative risk of one course of action over another became a politically loaded black and white issue. Battle lines were drawn and the media, Government and the medical profession were on one side; sceptical parents on the other.
I am prepared to concede that there may be a study which categorically states that MMR is safe, but if it exists nobody is shouting about it. What the Europen Union study did conclude was that whilst there were negative side effects from MMR, autism was not one of them.
From what I can gather from the World Health Organisation, measles kills around 158,000 children a year worldwide. That is a tragic number of deaths, and is certainly not to be taken lightly. But, none in the UK. That could be the result of MMR, but as the decline in measles deaths predates the MMR vaccine, it seems likely that the main reason why children die of measles is, as the W.H.O. point out, malnutrition and poor hygiene. Thankfully, rare in the UK.
I would not advise anybody either to have their child vaccinated or not. I am not a medical doctor. However, we should always remember that nothing is without risk. If you do not vaccinate your child there is a risk, still relatively small, that your child will contract measles. If your child contracts measles in the UK, the chances of them dying would appear to be relatively low, but a low risk is still a risk.
Unhelpfully, however, if you choose to vaccinate your child there is a risk that they will develop complications. It is hard to know what consequences these might have because the political controversy surrounding MMR has made it almost unthinkable that any medical researcher would risk their career by looking for evidence that it is unsafe. Such evidence that does exists suggests that in the majority of cases, particularly in ‘rich’ countries such as the UK, the complications will be relatively minor, and not life threatening.
My objection to the Getstats article is partly that it is pretty much devoid of statistics but mainly its moralistic tone which points the finger at parents who really are caught between a rock and a hard place. We should remember that statistics are tools of probability, but when it is your precious child that reduces to two possibilities: either they will be well or they will not. Given the evidence it is as rational to avoid the vaccine as it is to endorse it. Neither decision is unscientific, but the science (and the stats supporting it) are far from certain on either side.