People wonder why some stories just won't go away. Take for instance the theory that the thimerosal (mercury) in vaccines is related to autism. This seems like a simple enough question to answer via science. After all, this is the sort of thing that science is supposed to be good at.
But, to date there has been no conclusive study that disproves the relationship between mercury and autism. There have been a decent number of half baked ones that make a token attempt to answer the question. These are the ones that are normally referenced by people like Dr Paul Offit to prove their point.
This was a follow up study done for 1,403 children in Italy who participated in an earlier study of the efficacy trial of pertussis vaccines. The study looked at the two different groups of children who received different amounts mercury from the vaccines and looked to see if there was any difference in outcomes. They basically found that there was no real difference between the groups.
Now, where to start with what is wrong with the study.
First, the two groups are based on different amounts of mercury exposure. Most of the time when you are looking for side effects you would want to compare how a group that was exposured to the substance did compared to a group that wasn't exposed.
Second, the study group contained only one child with autism - so out of 1,403 there was only one child. Since the current estimation of autism is 1 in about 150 I would have thought that there would have been more children with autism found.
Third, this study is just looking at exposure to one vaccine. It does not appear that they attempted to control for other sources of mercury that the children were exposed to.
Last, this study was funded in part by the CDC but done on a group in Italy. Now I have nothing against Italy but why can't the CDC fund a study that looks at the thimerosal/autism issue in the US for US based children?
I will be happy when the research is finally properly done to put this issue to bed once and for all so everyone can stop arguing about it and move on to something else. But for now it is yet another study that doesn't show what it is says it does.