Map of life expectancy at birth from Global Education Project.

Tuesday, August 16, 2005

Thimerosal III: Let's get this over with

We have been discussing the crusade of Robert Kennedy Jr. to convince the world that the preservative thimerosal, once used in childhood vaccines, has caused a massive epidemic of autism. In previous posts, we have seen that Kennedy grossly misrepresents a meeting of public health officials in June 2000, at which a study that indicated a possible connection between thimerosal and autism was discussed. Kennedy falsely accused the participants of immediately believing that thimerosal did indeed cause autism, and immediately conspiring to concealing the truth from the public. On the contrary, the participants considered the evidence far from convincing, and discussed how best to investigate the question further.

Next, we discussed the purported epidemic of autism. We found that the data usually cited to show that there has been an explosive increase in the prevalence of the disorder is unreliable. While it is possible that the condition has become more common, the assertion that autism did not exist prior to thimerosal and that the prevalence has neatly tracked children's exposure to the compound is completely unsupported by any credible evidence.

In op-ed columns, Kennedy has claimed that "hundreds of studies" support a link between thimerosal and autism. When challenged, however, he has come up, not with hundreds, but with essentially two. One is the study by former CDC employee Tom Verstraeten, which triggered the 2000 meeting. Subsequent analysis of Verstraeten's data has led to the conclusion that there is no association after all. Kennedy claims this reanalysis was ordered by CDC officials, who demanded that the new analysis not find any link. The other is essentially a single study, but Geier and Geier, which has been republished in various forms several times. Kennedy also claims that the only evidence refuting the link between thimerosal and autism comes from two "disastrously flawed" European studies, though he does not say how the studies are flawed.

Sarah Parker, Benjamin Schwartz, James Todd and Larry Pickering reviewed the evidence concerning thimerosal and autism in the Sept. 2004 issue of Pediatrics. I doubt that my readers are interested in all the boring details of their analysis. The Geier and Geier studies depend on the Vaccine Adverse Events Reporting system, which is a passive, voluntary system. People who think their child was harmed by a vaccine may report the "event" to CDC. Obviously, people whose children become autistic, who believe that vaccination was the cause, create the cases in the system. To use this system as evidence that thimerosal causes autism is circular reasoning. There are many other problems with this methodology, just as serious, which I won't take the time to discuss. Geier and Geier also use the Department of Education data, which we discussed previously, and perceive an association over time between thimerosal containing vaccines and the prevalence of autism. The DOE data, however, represent children who are deemed eligible for special education services. They do not provide any information at all about the actual prevalence of autism in the population.

Four other cohort studies do not find an association between thimerosal exposure and autism. These include the Verstraeten study. Parker et al note that this data was reanalyzed prior to publication, to address methodological problems. They acknowledge that such reanalysis could introduce "investigator bias," whereby the investigator's beliefs could affect the outcome. However, their own careful review conclues the finding of no association is sound. There is not space here to get into the complexities of this, but Kennedy never does either and since he makes no specific assertions about how the reanalysis was invalid, there is nothing to refute.

The "disastrously flawed" European studies are actually by far the most rigorous. Denmark has a so-called "civil registration" system which contains reliable medical information on all citizens. This creates an enormous data set in which children's thimerosal exposure can be matched with autistic spectrum diagnoses. This analysis finds a negative association -- a lower incidence of autism -- for children who received any thimerosal containing vaccinations compared to those who did not, although the confidence interval just barely contains zero (i.e., there is about a 5% chance that there is no association, vs. vaccination actually being protective). They did find a long-term increase in the incidence of autism, but it continued after thimerosal was removed from vaccines in Denmark. The other "disastrously flawed" study, conducted in the UK, was a retrospective cohort study. This study also found a protective effect against autism of thimerosal containing vaccines. (Personally, I doubt very much that thimerosal actually protects against autism; but it is possible that either vaccination in general, better health care, or family ability to obtain well child care, are somehow associated with a lesser risk.)

Now, this is all quite dry and uninteresting. There are a lot more ins and outs, details, and specific assertions Kennedy has made that I could discuss. But it isn't worth it.

Here's why this matters. A lawyer, who is famous for being the son of a murdered politician, has gained a very prominent public platform -- including a lengthy article in a high-circulation magazine, op-eds in the nation's leading newspapers, and appearances on many of the big-time TV yackfests -- to claim that "they" -- the secretive, corrupt, unaccountable cabal of public health scientists -- are all conspiring to conceal from the world the horrifying truth that the entire medical institution -- drug companies, the FDA, the CDC, physicians the world over, medical journal editors, academic researchers -- have collectively inflicted a devastating disease on millions of children the world over; and what is more, they are continuing to do it in poor countries where thimerosal is still used. What is most remarkable about this conspiracy is the absolute unity and the inviolability of the oath of silence taken by all those hundreds, or probably thousands, of co-conspirators.

Maybe you've been home sick some time, or channel surfing between innings of the big game, and seen those informercials with the guy selling a book about the miracle cures "they" don't want you to know about. It turns out there's a simple, natural cure for cancer; heart disease; arthritis; you name it. The reason people have these diseases is because they are caused by prescription drugs. Statins are the cause of heart disease. But just send this guy money, and he'll tell you the cures "they" are keeping secret.

What Kennedy is doing is utterly reprehensible. Apart from the exploitation and abuse of families coping with the heartbreak of having an autistic child, he is attempting to cause severe damage to the culture. (Fortunately, despite the podium he has been given by irresponsible corporate media, he hasn't gotten much traction.) As I have said a thousand times, the democratization of science is critical to the future of democracy, indeed the future of humanity. That means we need to expose corruption and self-dealing in scientific enterprise, to be sure. But it also means that we must have respect for the cause of science, the quest for truth using human senses and reason, and the norms of honesty, openness, and intellectual integrity which the large majority of scientists and physicians try to honor.

Science is conducted by flawed human beings, working in flawed institutions. But it is not a conspiracy against the public. Kennedy deserves no respect, and no hearing, from anyone, ever again.

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