"Many valid scientific studies have shown there is no link between vaccines and autism," the statement continues. "The American Academy of Pediatrics supports further research into the causes of autism in hopes this will lead to optimal strategies for prevention, diagnosis and treatment."
Offit says Peet's approach sets her apart from other celebrities weighing in on the topic.
"[Peet] says, 'I'm not a scientist; you shouldn't even be listening to me,' which is refreshing," he says.
While the participation of Peet and McCarthy in the vaccination debate may make waves among the public, their convictions are unlikely to sway those of medical experts and autism advocacy groups.
"The risks [of skipping vaccinations] became no longer theoretical with the recent measles outbreaks, which have sickened 127 children in 15 states," Offit says. "Measles makes you sick. One out of every 1,000 kids who gets it dies from it, and one in five are hospitalized."
"We do not endorse vaccination for all children, and with the present schedule, because of the lack of safety testing and the number of reports from parents about losing their child after vaccination," counters Stan Kurtz, executive director of the advocacy group Generation Rescue, in an e-mail to ABCNews.com. "My child and Jenny McCarthy's child included."
But Offit says, no matter what science may say, there is little doubt that celebrity advocacy goes a long way in swaying public opinion -- and public health.
"We're in an information age more than any other time in history, and I think that's both good and bad," he says. "It's good because we have a lot of information to work with, but it's bad because some people think that's enough to make them experts. That's not true here."
This article was updated on Aug. 15 to include a statement from the American Academy of Pediatrics.