The high noon deadline for bioethicist Arthur Caplan’s $10,000 challenge to Rep. Michele Bachmann has come and gone without a peep from the Republican presidential hopeful. But damage from her statement linking the HPV vaccine with mental retardation has already been done, Caplan says.

As we reported last week, bioethicist Steven Miles first ponied up $1,000 to call Bachmann’s bluff. Caplan, a professor at the University of Pennsylvania, then raised the ante with $10,000 out of his own pocket. He asked Bachmann to produce a real person who has suffered mental retardation by the HPV vaccine.

If she could do it, Caplan offered to donate the ten grand to Bachmann’s charity of choice. If she failed, he suggested that Bachmann donate the same amount to a charity of his choice. No one from the Bachmann camp ever contacted Caplan accepting the challenge, according to the bioethicist.

“Time is up,” he said in a press conference today.

Over the past week, Caplan, who studies vaccine ethics, chastised Bachmann for her rumor- and fear-mongering of a vaccine that’s used to prevent cervical cancer. Despite medical professionals refuting Bachmann’s claim, Caplan wrote in a blog that he was still “worried that the stench of fear was going to linger around vaccines yet again.”

Miles concurred in an interview with NPR’s Michele Norris. “What happened here was yelling ‘fire’ in a crowded theater,” Miles said. “The claim is very important because women will make important health decisions based on the idea that mental retardation may be a side effect of this, which there’s no evidence, so far, that it is.”

Why have concerns about the vaccine grown so disproportionate to the small safety hazards it actually presents? Because politicians occasionally use anecdotes and stories instead of facts, Caplan says.

“Politicians shouldn’t get away with hearsay,” he said. “We need to hold candidates responsible for their sources.”

Caplan tells Shots that he’s received a lot of e-mails supporting his challenge — some people even offering money of their own — and a few trying to disprove him. But no one has succeeded yet.

And as one of millions watching the Republican Primary debate tonight, he’ll be listening hard for more talk of vaccines.