McCarthy later insisted that she had cured their son through a combination of diet and vitamins. She accuses the government of being afraid to confront "the truth" about vaccines. In the last year or so, although she now admits her son never had autism, she is still selling fear by talking about the schedule of vaccines as dangerous. She has put the full force of her celebrity to the task of convincing parents to leave their children vulnerable.

McCarthy makes the most sense viewed not through her celebrity lens, but as a fairly typical parent of a child facing a diagnosis of special needs. My son also has special needs, in his case Down syndrome, and I can tell you that the moment of diagnosis is hard and the days and months that follow are even harder. As I oscillated between hope and fear and tried to come to an understanding of my new life, I too looked for something to blame. Those powerful words, "Down syndrome," instantly transformed my life and the life of my family. I mourned for the loss of my idea of a "normal" son. Is it any wonder that McCarthy, having encountered the future laden with the word "autism," believed the myth of the vaccine and the hope for a cure? Is it any wonder that so many other parents have seized on this fraudulent accusation and related false hopes? I empathize with McCarthy, but that doesn't erase the real harm she has done.

Anti-vaccinators risk not only the lives of their own children, but also those of others who are too medically fragile to get vaccinated and must instead rely on "herd immunity." Many medical conditions, especially those which compromise the immune system (which is fairly common in the world of Down syndrome), make vaccines medically inappropriate. Happily, in a population of vaccinated people, infectious but preventable diseases have trouble spreading even to the immunocompromised. But herd immunity breaks down when vaccinations are not administered to all who can medically receive them. At that point, people who chose to refuse vaccinations endanger those who had no choice.

It's happening right now, as diseases long rendered unthreatening are roaring back into dangerous life. We've seen a rapid increase of outbreaks in preventable diseases, such as pertussis (whooping cough), measles, and mumps in the U.S. and the U.K. Whooping cough, for example, hit its highest rate of infection in 50 years over the last winter in the United States. A website dedicated to tracking the illnesses and deaths associated with the anti-vaccine movement cites over 100,000 illnesses and over 1000 deaths from these preventable diseases.

McCarthy joined this dangerous movement after her son turned two and began to experience seizures and speech delays. He was diagnosed with autism, and she seized on research out of England that linked vaccinations to autism. That research was fraudulent. In 1998, Andrew Wakefield, who had a financial stake in an alternative MMR (Measles-Mumps-Rubella) vaccine, published a study in The Lancet that argued for a causal link between the traditional MMR vaccine and autism. His study was a corrupt version of a "case-control" trial, a notoriously unreliable format, based on just 12 children with autism. Such a tiny trial, even if perfectly conducted (and it was not), could tell very little about the wider population. Multiple larger trials refuted Wakefield's conclusion; moreover, Wakefield was found to have manipulated the evidence. Wakefield was stripped of his license to practice medicine and The Lancet took the extraordinary step of retracting the article. For Wakefield and his backers, like McCarthy, it's all a sign of a conspiracy.