“If the surgeon general or the secretary of health or the head of the C.D.C. would come out and make a really strong statement on this, I think the whole thing would go away,” said Dr. Peter J. Hotez, president of the Sabin Vaccine Institute, who has a severely autistic daughter whose disease, he argues, is genetic.

Image Paul A. Offit, pediatrician. Credit... Ryan Collerd for The New York Times

Asked why public health officials have been reticent, the acting surgeon general, Dr. Steven K. Galson, issued a statement saying that “childhood immunizations are one of the greatest achievements of all time” and that “scientific evidence clearly shows that vaccines do not contribute to autism.” He has spoken on issues like obesity, tobacco, air travel and exercise, but his office said he had not been questioned by journalists about vaccines and autism.

Dr. Offit’s book, published in September by Columbia University Press, has been widely endorsed by pediatricians, autism researchers, vaccine companies and medical journalists who say it sums up, in layman’s language, the scientific evidence for vaccines and forcefully argues that vulnerable parents are being manipulated by doctors promoting false cures and lawyers filing class-action suits.

“Opponents of vaccines have taken the autism story hostage,” Dr. Offit said. “They don’t speak for all parents of autistic kids, they use fringe scientists and celebrities, they’ve set up cottage industries of false hope, and they’re hurting kids. Parents pay out of their pockets for dangerous treatments, they take out second mortgages to buy hyperbaric oxygen chambers. It’s just unconscionable.”

His opponents dismiss him as “Dr. Proffit” because he received millions in royalties for his RotaTeq vaccine. One group he criticizes harshly in the book is Generation Rescue, which advocates treating autistic children with wheat- and dairy-free diets, vitamins and chelation to remove mercury from the body. Ms. McCarthy, her companion, the actor Jim Carrey, and Deirdre Imus, wife of the radio host, are all on its board.

J. B. Handley, who founded Generation Rescue in 2005, rejected Dr. Offit’s attacks, saying: “We have hundreds of fully recovered children. I’m very frustrated that Dr. Offit, who’s never treated an autistic child, is spending his time trying to refute the reality of biomedical recovery.”

He scoffed at the idea that Dr. Offit had had numerous death threats but condemned threats generally, saying he had received some himself. “No one should ever do that to another human being,” he said.