MMR vs Autism - Amateur Epidemiology
Once again, the headlines declare, "No link between autism and MMR vaccine".
The story, however, is a different matter:
The study, published on Tuesday in the Archives of Disease in Childhood, found no evidence of any abnormal biological response from the shot that could point to a link between the vaccine and autism.
Hmm... an absence of evidence of a link does not mean evidence of the absence of a link.
"This study really supports the view these are safe vaccines," said David Brown, a researcher at Britain's Health Protection Agency who worked on the study. "The evidence is now so solid there really isn't a need for further studies here."
Same old guff that's been said at the conclusion of a number of other studies, all of whom appear almost deliberately to have been set up to provide statistics that imply the absence of a link. Perhaps the most famous is the "Danish study". The study demonstrated that there was actually a higher risk of autism among those who did not receive the MMR. What was not noted in that study is that it occurred at a time when the suggestion of an MMR / autism connection was big news, so those children already at risk of autism were more likely to turn up in the group of children whose parents refused to give their children MMR. A self-selecting study is no study at all.
As Jackie Fletcher of JABS puts it:
It is making a leap from having the actual data on the antibodies and saying MMR does not cause autism.
Persistent measles infection is only one of the theories on why there appears to be a connection between the MMR vaccination and autism - my favourite explanation by far is that there are children at risk from autism, and that every time their bodies are put under significant stress (such as the high fevers associated with vaccination), there is a chance that a regression will be triggered. That's a very loose theory, granted, but there are others - one very interesting suggestion is that the study quoted in today's news articles focuses on children aged 10 - 12, and if those children had persistent measles infection from vaccination at or around 2 years old, it would not be evident from antibodies in the bloodstream, but in the spinal column. I don't know how true that claim is, though.
Now, you might say that the studies that have suggested a link between MMR and autism are also biased in their construction, and designed to give the results that would imply such a link.
I agree.
An appropriate study, in my opinion, would be to select candidates who are "at risk" from autism - where a member of the family has autism, or where a member of the family is an engineer, or where there is higher-than-average incidence of college education - and follow their babies from birth through age five or so. Some of the group would be given the MMR in one visit, as is the current method of operation, others would be given separate Measles, Mumps and Rubella shots in three visits, several weeks apart. A little tricky to do this as a double-blind study, but not impossible - the MMR patients would simply receive a saline shot instead for two of their three visits.
Such a study would get over the issue that, with an incidence rate of 1 in 150, and only a fraction of that being suggested as related to MMR vaccination, autism causes disappear into statistical noise; such a study also allows for possible weighting factors to be recognised and balanced (by assigning study members such that particular combinations of weighting factors appear more or less equally in each cohort), in a way that has not been possible, or not been tried, with other studies.
While there are many irrational views on both sides of this debate, sadly it seems as though these are the views that make the loudest noise.
A scientific approach to this discussion has not yet been considered, in my opinion.
Most parents of autistic and at-risk children I have spoken to (and granted, that's not in the hundreds that would be required for a good sample) are not looking to make the choice between MMR or not vaccinating their children - they are artificially limited by the government to making that choice. The lack of availability of individual vaccines for Measles, Mumps and Rubella makes the choice one of "MMR and possible-to-likely autistic regression" versus "possible measles, mumps or rubella infection - maybe in someone else's kid". I think that particularly when it comes to illnesses like Rubella, where the risk is to the in-utero fetus of an infected mother-to-be, perhaps we ought to consider whether it is safer to vaccinate girls as they approach their fertile years, rather than vaccinating everyone a year or two after birth, in an attempt to provide "herd immunity".
Another thing I'm not looking for is to blame all (or even most!) cases of autism on the MMR vaccine, or thimerosal, or any of a number of other causes. There are so many stories of autistic onset, from the kid who "everyone could see he was different from the moment he was born", to the kid who develops normally into a babbling toddler and then suddenly shuts up and retreats into his mental cocoon over the course of a few days. Clearly, there's a genetic component that at least creates a susceptibility, but for something to happen so suddenly, and so coincidentally "on time", it seems like there has to be an environmental component that acts like a trigger.
With the government continually feeding us crap science, and no physical method to reliably screen for a majority of autism cases, it's no wonder many parents feel like emulating their children at their worst autistic moments, repeatedly banging our heads against the wall, because it's better than not knowing why our heads hurt.