Diagnoses of autism are unquestionably on the rise in the United States, and parents and other friends and family of autistic children are understandably looking for answers. At a time, there was some plausible speculation that thimerosal, an additive in some vaccines, might be a cause of autism. The claim was investigated, as it should have been, but it turns out not to be true. Nevertheless, as tends to be the case with these things, some people still believe in the autism-thimerosal link despite the debunking evidence. Some people including, it seems, John McCain who thinks "there's strong evidence" of the autism-thimerosal link even though there is, in fact, no such evidence.