Via the ABC News blog Political Punch comes news that senator and Republican presidential candidate John McCain has taken a strong stance on the discredited link between vaccination and autism… a stance contrary to scientific consensus. Here’s what Jake Tapper wrote:

At a town hall meeting Friday in Texas, Sen. John McCain, R-Ariz., declared that “there’s strong evidence” that thimerosal, a mercury-based preservative that was once in many childhood vaccines, is responsible for the increased diagnoses of autism in the U.S. — a position in stark contrast with the view of the medical establishment.

McCain was responding to a question from the mother of a boy with autism, who asked about a recent story that the U.S. Court of Federal Claims and the National Vaccine Injury Compensation Program had issued a judgment in favor of an unnamed child whose family claimed regressive encephalopathy and symptoms of autism were caused by thimerosal.

“We’ve been waiting for years for kind of a responsible answer to this question, and are hoping that you can help us out there,” the woman said.

McCain said, per ABC News’ Bret Hovell, that “It’s indisputable that (autism) is on the rise amongst children, the question is what’s causing it. And we go back and forth and there’s strong evidence that indicates that it’s got to do with a preservative in vaccines.”

McCain said there’s “divided scientific opinion” on the matter, with “many on the other side that are credible scientists that are saying that’s not the cause of it.”

The established medical community is not as divided as McCain made it sound, however. Overwhelmingly the “credible scientists,” at least as the government and the medical establishment so ordain them, side against McCain’s view.

Moreover, those scientists and organizations fear that powerful people lending credence to the thimerosal theory could dissuade parents from getting their children immunized — which in their view would lead to a very real health crisis.

Over at Respectful Insolence, Orac has already taken this one on (and has blogged quite a bit about this topic in general before). In short, based largely on circumstantial evidence, the idea emerged in the 90s that mercury-containing preservatives (particularly thimerosal) found in vaccines were responsible for the increased number of cases of autism reported in recent years. However, it cannot be stressed enough that this link has been thoroughly discredited, and McCain’s view on the subject is not one held by the scientific community.

Now, I don’t expect a president–much less a presidential candidate–to be well-versed on all scientific topics. But, what’s striking about this is just how definitively McCain has stated his position on this issue, especially compared to some of his past waffling. This is the same man who last year couldn’t say whether condoms help prevent the spread of HIV! Coupled with McCain’s past support of teaching intelligent design in schools, a not-so-rosy picture emerges regarding McCain and science.

Orac succinctly explains why this latest revelation is particularly disturbing:

This is worse, though, than pandering to creationists. Presidents don’t have much power to determine how evolution is taught at the local school lever, but he does have enormous power over the public health apparatus of the nation in the form of the CDC, FDA, and NIH. Encouraging antivaccinationists can lead to a public health disaster in the form of the resurgence of vaccine-preventable diseases.

Vaccines are effective. Period. And, universal vaccination forms one of the fundamental pillars of modern medicine. Although the anti-vaccination movement is very marginal, it becomes truly dangerous if it is able to convince significant numbers of parents to prevent their children from being vaccinated against otherwise preventable diseases. By lending his own credibility to this pseudoscientific nonsense, McCain is committing a scientific sin bordering on unforgivable.

In this case, I’m inclined to believe that McCain has just been subject to poor scientific advice. However, if that is the case, he needs to find new scientific advisors pronto… at least if he wants to maintain any shred of credibility within the scientific community.