Republican presidential contenders in need of an opening to attack frontrunner Rick Perry, particularly Michele Bachmann, have been hammering away at his nullified executive order mandating that young Texan girls receive vaccinations for HPV, a common infection that can lead to cervical cancer.

Part of the criticism revolves around a potential conflict of interest stemming from Perry accepting campaign donations from Merck & Co., a pharmaceutical company that manufactures the vaccine Gardasil. Rep. Michele Bachmann, R-Minn., asked whether Perry's order was about life or was it about millions of dollars, and potentially billions, for a drug company, a valid question given the fact that Merck has given Perry $23,500 in campaign contributions, including $5,000 in 2006, the year he issued the order. Merck has also given $380,000 to Republican Governor's Association since 2006, the year that Perry became a prominent member in the RGA.

But Bachmann took things a step further when she implied that Gardasil can have serious side effects, warning ominously about little girls who have a negative reaction to this potentially dangerous drug. In subsequent interviews Bachmann recounted meeting a woman whose daughter had suffered mental retardation as a result of that vaccine.

Exposed to the scrutiny of medical professionals, Bachmann's claims do not hold up. O. Marion Burton, president of the American Academy of Pediatrics, said there was no evidence linking the vaccine to mental retardation.

There is absolutely no scientific validity to this statement, Burton said in a statement. Since the vaccine has been introduced, more than 35 million doses have been administered, and it has an excellent safety record.

Dr. Kevin Ault, an associate professor of Gynecology and Obstetrics at Emory University and an investigator in the clinical trials for Gardasil, reached a similar conclusion when New York Magazine asked him about the retardation claim, saying he'd not heard that one before. He added that side effects reported by people who had used the vaccine could not be conclusively linked to the drug.

There's been a nice study from the [Centers for Disease Control] that basically [showed that] if you compare a group of people who got the vaccine to a group of people who didn't get the vaccine, all these things are rare and they occur equally in both groups, Ault told New York Magazine.