Regarding the scope of the book: One commenter asked if I had considered including material in the book that was not directly related to the vaccine-autism debate. Yes. The one area that I didn’t address was the history, scope, and impact of the anti-vaccine movement in the United States. There is probably no more powerful influence on how many parents make decisions about vaccines than that of the cynically named National Vaccine Information Center. This group, using a variety of scare tactics, consistently puts out misinformation about vaccines on their website. I would have liked to have spent some time in the book describing the origins of this group, their ties to personal-injury lawyers, and their influence on Congress.

Regarding the child on the cover of the book: One commenter asked why I had chosen to put an unclothed child on the cover, viewed from the back. This wasn’t my choice, but rather the choice of the art director at Columbia University Press. The drama of the picture owes to the fact that the child is viewed from the back (remember the picture of Babe Ruth viewed from behind, kneeling in the on-deck circle in his later years) and is exposed from the waist up. My concern with the picture is that one could argue that this child is too young to be reasonably given the diagnosis of autism spectrum disorder.

Regarding the recent ruling by the Georgia Supreme Court: On October 6th, 2008, the Georgia Supreme Court ruled in favor of a couple who wanted to directly sue vaccine makers on behalf of their autistic child, claiming that thimerosal in vaccines had been the cause. This ruling appears to be in direct contradiction to the National Childhood Vaccine Injury Act (NCVIA) of 1986, which protected vaccine makers from initial lawsuits against vaccines by creating a Vaccine Injury Compensation Program managed through a federal claims court. Previous appeals to state supreme courts in New York and Pennsylvania have failed to circumvent this Act. What some may not realize is that despite the NCVIA, a parent can still sue vaccine makers directly; they just have to wait until their case has failed both in this federal vaccine court and the court of appeals. The goal of the lawyers appealing to the state Supreme Court in Georgia was simply to skip a step. Historically, claims that have failed in the federal vaccine court and the federal court of appeals have fared poorly in state courts, so lawyers have been reluctant to take these cases. However, if lawyers can make their initial claims directly to juries in state courts, instead of first having to make them in front of federally appointed judges in federal vaccine court, they are more likely to win. All of this is very bad news for children. Vaccines are not big moneymakers for pharmaceutical companies. If this Georgia ruling stands–and parents directly sue vaccine makers without first going through the Vaccine Injury Compensation Program–we might end up right back where we were before the Program was created and manufacturers were on the verge of completely abandoning vaccines for American children. Again, the perceived rights of the individual will trump the rights of society.

Regarding my characterization of children with autism: I think one of my limitations in writing this book is that I’m not a neurologist, psychologist, or developmentalist. I’m an infectious diseases specialist with an expertise in vaccines. So I don’t come in contact with many children with autism. As a consequence, my characterization of children with autism in AUTISM’S FALSE PROPHETS came exclusively from what I read in newspapers, which no doubt slants descriptions to more extreme symptoms, or to descriptions from a handful of people, like Richard Grinker, Peter Hotez, Kathleen Seidel, and Camille Clark. I think that the limited number of descriptions of children with autism failed to include children on the milder end of the spectrum.

Regarding my comment that vaccine introduction into developing countries decreases family size: The commenter is correct in assuming that families get smaller because parents decide to have fewer children, realizing that not as many will die from infections.

Regarding the culture of celebrity: I was speaking at a statewide immunization conference in St. Louis last week and a physician asked what I thought about Amanda Peet’s entry into the debate about the importance of vaccines. My sense is that in a more perfect world the media would look to clinicians, public health officials, and scientists for information about science and medicine. But we don’t live in that world. It’s not only that entertainment television hosts like Oprah Winfrey and Larry King seek out people like Jenny McCarthy for healthcare advice, Sanjay Gupta on CNN does the same thing, recently interviewing Aidan Quinn and Matthew McConaughey on their concerns about the safety of vaccines. So, I think Amanda Peet represents an important counterpoint to actors like McCarthy who unnecessarily scare the public about vaccines. And, given the amount of hate mail that Ms. Peet has received, I think it’s very brave of her to do it. She defends vaccines simply because she thinks it’s the right thing to do, without any apparent direct benefit to her or her career.

Regarding Jennifer’s comment that the stated previous incidence of autism of 1 in 10,000 children is inaccurate: You’re right. I’ll make sure not to use that statistic in the future. Thanks for pointing that out. As you note, the incidence is closer to 1 in 2,500.

Regarding the financial impact of vaccines: The CDC always performs a cost-benefit analysis to determine whether the anticipated savings in healthcare costs and indirect costs (i.e., lost time from work) justifies the price of a vaccine. But I suspect that your question is broader than that. I’ve heard a Harvard economist (Bloom) describe the impact of vaccines when they first enter a developing country. He makes the point that family sizes start to get smaller and economies improve. His point being that not only does wealth make health (although you could argue that one in the US) but that health makes wealth.

Regarding autoimmunity triggered by vaccines as a possible cause of autism: It is certainly true that infections can trigger autoimmune responses (e.g., streptococcal infections as a cause of rheumatic fever, campylobacter infections as a cause of Guillain Barre Syndrome, or Borrelia burgdorferii [Lyme disease] as a cause of chronic arthritis). However, there remains no clear evidence that vaccines induce autoimmune responses. Probably the best example is Lyme disease, where arthritis appears to be mediated by T cell responses to the outer surface protein OspA, the same protein contained in the vaccine. But two large studies have clearly shown that Lyme vaccine does not cause chronic arthritis. The point being that vaccines are generally too wimpy to meet the four criteria necessary for induction of autoimmune responses: First, autoreactive T or B cells must be present. Second, self-antigens must be presented to the immune system in quantities sufficient to cause autoreactive cells to divide and mature. Third, additional signals such as cytokines are required to activate autoreactive T and B cells. Fourth, regulatory T cells must fail to control destructive autoimmune responses. Only when all of these conditions are met will expansion and activation of autoreactive lymphocytes and progression to autoimmune disease occur. No vaccine has been shown to meet these four criteria. Finally, pathogenetic studies of the brains of autistic children have consistently failed to show evidence that the disorder is immune mediated.

Regarding scientists standing up for good science: I think that scientists have been reluctant to enter the vaccine-autism fray for many reasons. The skills required to perform good science, write scientific papers, and present data in front of a scientific audience are different from those required to describe science to a reporter or reduce complex issues to sound bites on television. And standing in front of a national television audience is not a natural act. Also, to bastardize Dickens, the media is an ass. Scientists actually believe in truth. It make take weeks or months or years to get to that truth, and one may never get to it, but I think we believe that it’s there. And although I have encountered several people in the media who really do want to get it right, most are just interested in holding the whetted finger to the wind and promote controversy even when a scientific controversy doesn’t exist. All under the journalistic mantra of balance, when public education is better served by perspective. For many scientists, this is a very hard process in which to participate.

It’s now been about ten years since vaccines were first blamed to be the cause of autism. First, it was the MMR vaccine. The mechanism by which this vaccine was supposed to cause autism was ill conceived. Measles vaccine virus was proposed to replicate in the intestine causing chronic inflammation and loss of intestinal barrier function allowing for entrance into the bloodstream of encephalopathic proteins causing autism. However, there was no evidence that attenuated measles virus damaged the intestine and no evidence that specific encephalopathic proteins caused autism. Despite the absurdity of the hypothesis, tens of millions of dollars were spent performing many epidemiological studies showing that it was wrong. More recently, in a study by Mady Hornig, the premise on which the hypothesis was based–namely that measles vaccine virus replicated in the intestines in children who later developed autism–was also shown to be wrong.

Then we moved seamlessly to hypothesis number two–that the ethylmercury containing preservative thimerosal caused autism. This, too, was based on a nonsensical notion. Given that the signs and symptoms of mercury poisoning were quite distinct from those of autism, and given that the quantity of mercury contained and likely to accumulate from vaccines was less than a child would encounter in the environment, the hypothesis was ill founded. Still, in response to growing parental concerns, six epidemiological studies were performed showing that thimerosal-containing vaccines did not cause autism. Again, tens of millions of dollars were spent to address a hypothesis that had no rational basis.

But the anti-vaccine forces press on. Now we’ve moved to something that anti-vaccine advocacy groups have been saying for years–it’s just too many vaccines given too early. Let’s compare children who have received vaccines with those who haven’t, they argue. Again, the premise is not grounded in rational pathogenesis. To assume that too many vaccines are the problem, one would have to assume that there is evidence that autism is immune mediated. No such credible evidence exists. Also, as has been pointed out by several of you who have commented on this blog, such a study would be unethical. That vaccine-preventable diseases occur and that vaccines prevent them is not a matter of debate–one cannot follow unvaccinated children prospectively in good conscience. So, the study could only be done retrospectively and would be fraught with bias, primarily differences in healthcare-seeking behavior. And even if performed and performed well, it would not end the debate. Because those who believe that vaccines are causing chronic diseases will never be swayed by data.

It seems to me that if autism advocacy groups gave a damn about children with autism they would demand that we give up the vaccines-cause-autism hypothesis and focus on the wealth of studies pointing to neuronal and developmental proteins expressed in utero or early in development. These studies provide the only reasonable road out of the darkness and into the light.

I’ll start with the easier questions.

We tried to get companies that publish audio books interested in this book, but were unsuccessful.

All of my royalties from the sale of this book will be donated to the Center for Autism Research at Children’s Hospital of Philadelphia. I have found the director of the center, Bob Schultz, to be a careful, thoughtful investigator. But this isn’t set in stone. I’m open to other suggestions.

I wrote the chapters introducing Wakefield and thimerosal without providing any evidence to refute those theories because that was the way it played out in the press and to the public. I thought that this would give the reader a better sense of what really happened during the early stages of the controversy.

Many bloggers continue to question whether mercury in vaccines causes autism. Given the amount of information available to refute this claim, I find this astounding:

First, prior to its removal from vaccines in the spring of 2001, it was possible that children less than 6 months of age could receive as much as 187.5 micrograms of ethylmercury in thimerosal. But because mercury is part of the earth’s surface, and is contained in our water, that wouldn’t have been their only source of mercury. A typical breast fed child would receive about 360 micrograms of environmental mercury, methylmercury. Because environmental mercury is eliminated from the body 10 times more slowly than the ethylmercury in thimerosal, it is much more likely to accumulate.

Second, six epidemiological studies consistently showed that children receiving thimerosal-containing vaccines were not at greater risk for autism than children receiving lesser quantities of thimerosal or no thimerosal in vaccines.

Third, within months of thimerosal’s removal from vaccines in 2001, the quantity of ethylmercury to which young infants were exposed dropped from 187.5 micrograms to 0 micrograms, without any appreciable decline in the incidence of autism. No single-dose vial of vaccine given to young children currently contains thimerosal.

Fourth, the signs of symptoms of mercury toxicity, as described in a wonderful article by Karin Nelson and Margaret Baumann referenced in the book, are distinct from autism. So it never made sense that mercury would cause autism.

Fifth, the reason that the American Academy of Pediatrics pushed to remove mercury quickly from vaccines is that there were not studies in place showing that the quantity of thimerosal in vaccines didn’t cause subtle signs of mercury poisoning. But no longer. The study by William Thompson and coworkers at the CDC answered that question. Thompson carefully defined mercury exposures before and after birth in about 1,000 children then prospectively performed more than 40 neurodevelopmental and psychological tests. Again, no differences in children exposed to greater or lesser quantities of mercury in vaccines. So thimerosal didn’t cause even subtle signs of mercury poisoning. Given that young children were exposed to more mercury from their environment than from vaccines, the results of Thompson’s study weren’t surprising.

So the epidemiological, ecological, and biological studies were all consistent.

A couple of bloggers praised the book for its tone, that I never appeared to get angry at the false prophets described in the book. The reason for that is that I’m not the father of a child with autism. If I were, I would have been quite angry. Angry because I think that the anti-vaccine forces have taken the autism story hostage. And angry that because of their influence, the media almost never carries stories about the real cause or causes of autism. In the July 11, 2008 issue of SCIENCE, Jim Sutcliffe summarizes the functions of the 30 or so genes that have now been associated with autism. A pattern is clearly emerging. Those genes code for proteins that involve the neurological synapse or proteins that are important in endocytoplasmic trafficking in neuronal cells. These kinds of studies might well lead to therapies that could modify the disorder. But you never hear about them. Never. Rather, we hear about how Jenny McCarthy treats autism by focusing on the gut–anti-fungals, elimination diets, etc. The media is perfectly willing to mislead parents for ratings. Shameful.

There is no known cause or cure for autism. But in the late 1990s two hypotheses garnered a great deal of media attention. The first, advanced by a gastroenterologist in London, posited that the combination measles-mumps-rubella vaccine (MMR) caused autism. The second, advanced by parent advocacy groups in the United States, argued that thimerosal, an ethylmercury-containing preservative that had been used in vaccines since the 1930s, was responsible. The notion that vaccines caused autism wasn’t surprising; vaccines have often been blamed for chronic disorders such as asthma, allergies, diabetes, multiple sclerosis, epilepsy, and mental retardation.

In response to the concern that vaccines caused autism, the public health and academic communities responded, performing a series of large, carefully controlled, epidemiological studies. Ten separate groups of investigators found no link between MMR and autism and six groups found no link between thimerosal and autism. Because of the strength, consistency, and reproducibility of these studies, the notion that MMR or thimerosal cause autism is no longer a scientific controversy.

The reason that I wrote the book is because of what happened after the studies exonerating vaccines had been performed and published. The media, using the journalistic mantra of balance, continued to cover the story as if it were a controversy. But the controversy is between those who believe in science as a way to answer scientific questions and those who don’t. The “vaccine-autism controversy” is really an anti-science story. Science is viewed by many in the media as just one more opinion in a sea of opinions.

The continued portrayal by the press that vaccines might cause autism has done a lot of harm. Harm because many parents are choosing not to vaccinate their children, witness the recent measles epidemic in the United States, the largest in more than a decade. Harm because the false notion that vaccines cause autism has caused parents to choose dangerous therapies, such as chelation. And harm because the notion that vaccines might be the problem continues to divert resources away from far more promising leads. My hope for this book is that people confused about this subject will see the sand on which the notion that vaccines cause autism is built. And also get a better look at the motivations of the fringe scientists, lawyers, journalists, and parent advocates who continue to flak for the irresponsible notion that vaccines cause autism.