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Vaccine expert Dr. Paul Offit is the author of the new book Deadly Choices: How the Anti-Vaccine Movement Threatens Us All
Dr. Offit discussed many of these same topics last night on The Colbert Report.
This interview is abridged. The full version was originally published at The Thinking Person's Guide to Autism.
What is your elevator pitch for parents concerned about vaccines and autism?
I think raising the concern is reasonable. Children get vaccines, and for some children, the signs and symptoms of autism may appear soon after receiving the vaccine, so asking those questions is reasonable.
The good news is that the question is answerable. Everything we know about autism tells you it's not the vaccines; why are we still focusing on this?
The anti-vaccination camp frequently demands to know why a vaccinated vs. vaccinated study hasn't been done. The reply is usually that such a study would be unethical.
You're right, [a vaccinated/unvaccinated study] is unethical. There's not an institutional review board in the world that would approve that kind of study, because we know that vaccines work, we know that if you don't give a large number of children vaccines that some of them are going to get whooping cough or chickenpox, some of them may be hospitalized or even killed by the diseases -- you can't do that kind of study.
People who believe their children's autism is vaccine-caused seem to mistake coincidence or correlation for causation. Can you give us an example of how that happens?
We're always looking for reasons why something happened. The example I use is from my wife, who is a pediatrician. She was about to vaccinate a four-month-old baby, and while she was drawing the vaccine from the syringe, the baby had a seizure -- and went onto have a permanent seizure disorder.
Now, my wife hadn't given the vaccine yet. But if she had given that vaccine five minutes earlier, there would have been no amount of statistical data in the world that would have convinced that mother that the vaccine hadn't caused the baby's seizure. You can do studies that show no increased risk with vaccines and seizure disorders, but that mother might still say "well, that's true for the population but it's not true for my child."
Temporal associations are powerful, and they're hard to defeat with statistics or studies.
Could you discuss the concept of herd immunity, specifically what it takes to establish it and protect public health?
Herd immunity simply means that you can stop the transmission of a virus or bacteria by having a critical number of the population immunized, and that number really depends on the nature of the virus or bacteria.
For example, Polio was introduced in the United States in 1955. When we got about 70 percent of the population immunized, that effectively eliminated polio, so it couldn't spread anymore. We eliminated polio from the U.S. by 1979.
Now, measles is much different, much more contagious than polio; you need a higher percentage of the population immunized. Overall the U.S. is in the high 80/low 90 percent immunization rate for measles, but there are certain communities where it's less than that, about 75 percent, and that's not good enough. When we had a measles outbreak in 2008, higher than anything we'd seen in a decade, it was in the communities with an erosion in vaccination rates -- Southern California, Upstate New York.
You also need to remember, there are about 500,000 people in the United States who can't be vaccinated, because they're getting chemotherapy for cancer, or are on immunosuppressant therapy for transplants or other disease. There are also kids younger than six months old who can't get the flu vaccine or are inadequately immunized against whooping cough because they're just starting their series. Herd immunity protects them.
People still hold chickenpox parties, and think of chickenpox as a mild childhood disease. But measles can be serious -- Roald Dahl's daughter Olivia died from measles encephalitis, and in your book you listed some rare but fairly gnarly potential measles side effects, including necrotizing fascitis.
