He wanted to give them the kind of pushback doctors have come to expect in affluent parts of Los Angeles and California, where increasing numbers of parents are refusing to inoculate their kids against contagious, even life-threatening diseases for fear of complications.
The salt-and-pepper-haired Offit slipped straight into character and zeroed in on one young doctor.
"I know you doctors keep telling me that vaccines don't cause autism. If that's true, then why is it on this package insert?" he asked, playing the role of a parent who had read the blogs and heard the celebrities who connect the two.
Shifting in her seat, the designated victim shot Offit an unsure look.
Then she began citing studies and said that drug packaging inserts include many "temporally associated symptoms" that weren't necessarily caused by the vaccine.
"Why?" Offit pressed. "Why would they put that there — just to scare me?"
The doctor kept trying. "They're required by law," she said. "I actually didn't know the answer."
Offit broke character to explain: Drug companies must list any condition known to have occurred within six weeks of a vaccination, whether the medication caused the condition or not, and even if it occurs at the same level as with a placebo.
Package inserts are legal documents, not medical documents, he said, calling them "the bane of [his] existence."
"If you look at the original package insert for chicken pox vaccine, it says, 'Broken leg has been associated with this drug,'" he added.
Studies have firmly debunked the notion that vaccines cause autism. Yet that is one of the most common claims made by a persistent national anti-vaccination movement that treats Offit as public enemy No. 1.