An American mother who lost her daughter to chicken pox 13 years ago continues to fight against the magical thinking required of the new “McCarthyism” — whose adherents believe the measles vaccine causes autism spectrum disorder (ASD).

Five-year-old Abby Peterson died in 2001 after contracting pneumonia as her immune system fought the chicken pox, dying in her mother Shannon’s arms after 10 hours in the hospital. Though both infections are preventable by vaccines, the bereft mother says a hippy dippy pediatrician discouraged her from immunizing her daughter.

“I asked for them and my doctor talked me out of it,” Peterson told ABC News this week. “He said vaccines were too new and recommended I expose my children to diseases instead because he felt they could build up their immunity naturally.”

As some parents in America and Western Europe question mandatory childhood vaccinations, Peterson says she wished she too had questioned the dominant paradigm — in this case, a free-thinking clinician suspicious of the measles, mumps, and rubella (MMR) vaccine, among others. Yet Abby’s particular susceptibility to infection was only discovered by autopsy when technicians found she’d been born without a spleen, an organ that is vital to a healthy immune system.

Still, the vaccines would have likely prevented Abby’s death, Peterson says. During the past dozen years, the Sleepy Eye, Minn., mother has implored her state legislature to pass mandatory childhood immunization laws, criticizing the minority of parents who refuse to vaccinate their children for fear of a purported link between MMR shots and the development of ASD, a chronic condition whose rising prevalence scientists cannot explain.

The comments came as TV host Jenny Mccarthy defended her views on childhood immunizations, which she says caused her son Evan to develop ASD — a chronic condition “cured” soon afterward with alternative treatments, in her view.

“Not vaccinating is not taking full medical care of your child,” Peterson told ABC News on Sunday.

Although Peterson and McCarthy both lack medical degrees, most medical organizations including the Centers for Disease Control and Prevention (CDC) and the World Health Organization vouchsafe for the safety and effectiveness of today’s vaccines. William Schaffner, a medical professor at Vanderbilt University, says the evidence is clear: “Vaccines have virtually wiped out a number of diseases that used to plague this country –- and they do not cause autism.”

Schaffer criticized McCarthy’s view that vaccinology is a scientific “gray area” necessitating the empowerment of parents to choose vaccine and dose regimens for their children a la carte. “The area is not gray. There is no injury to children getting vaccinations simultaneously,” he said. “A child’s immune system is more capable, powerful and flexible than you would think it is.”

The anti-vaccine movement gained traction early last decade as parents struggled to explain the rising prevalence of ASD in America, a condition affecting as many as one in 88 children, the CDC says. Much of the “evidence” supporting a link between MMR shots and ASD was based on a now debunked article published in 1998 by The Lancet, whose author Tim Wakefield used faulty data to draw the conclusion.

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