We have an anti-vaccine president. One of my concerns about Trump the candidate was that one of his most consistent positions over the years was blaming vaccines for the alleged autism epidemic (there isn’t one, by the way). Once elected it did not take long for this to manifest as a policy priority. In January Trump met with RFK Jr. to discuss him heading an Orwellian commission on vaccine safety and scientific integrity.

At a recent meeting with educators, Trump continued to express his false belief in a “tremendous increase” in autism:

“Have you seen a big increase in the autism with the children?” Trump asked Jane Quenneville, the principle of a Virginia public school that specializes in special education. Quenneville responded that she had. Trump continued: “So what’s going on with autism? When you look at the tremendous increase, it’s really such an incredible — it’s really a horrible thing to watch, the tremendous amount of increase. Do you have any idea?”

“The autism?” Really?

As I have discussed many times before, scientists have actually looked carefully at autism incidence and prevalence and found that there is little evidence for any real increase. The apparent increase is due to broadening the definition, increased surveillance, and diagnostic substitution. The problem here is that Trump has a fixed idea and he does not correct that idea when confronted with scientific evidence and expert opinion. That in itself is a scary thought.

We have not heard much since Kennedy announced that the president had spoken to him about forming a vaccine commission. Recently, however, Kennedy held a press conference with Robert DeNiro (also anti-vaccine) and other anti-vaxxers to once again fearmonger about the dangers of thimerosal and vaccines.

Kennedy is now pulling the “show me one study” gambit, with a $100,000 reward for anyone who can point to a single peer-reviewed study that shows thimerosal as currently included in flu vaccines is safe. There is no proof in one study. Consensus emerges from many studies repeatedly showing the same finding.

This is a classic denialist strategy – try to seem reasonable by just asking for evidence. But the implication is that the evidence which already exists is insufficient. You can always ask for more evidence, or find some reason to dismiss the evidence that exists.

It would be more appropriate to have a panel of independent scientists evaluate all the scientific literature on thimerosal and determine if the evidence is sufficient to conclude that the doses of thimerosal currently in some vaccines is safe. Oh, wait. That has already happened. Multiple times.

Here is a compilation of 10 studies I put together for SBM all showing no association between thimerosal and autism. There have been more studies since then showing no association. Perhaps most telling is the fact that in 2001 thimerosal was removed from the routine childhood vaccine schedule. At the time anti-vaxxers predicted that autism rates would plummet. They never did. Here we are 16 years later and the removal of thimerosal had zero effect on autism incidence. There is no way to avoid the implications of this clear fact – thimerosal never had any measurable effect on autism.

Kennedy is also now misrepresenting a CDC study on the relative toxicity of ethylmercury (the form in thimerosal) and methylmercury (the form found in seafood, for example). He writes:

The CDC has long answered that nettlesome question with the controversial claim that ethylmercury in vaccines is not toxic to humans. Now, two CDC scientists have published research decisively debunking that assertion. As it turns out, there is no “good mercury” and “bad mercury.” Both forms are equally poisonous to the brain.

First, he misrepresents the CDC position on ethylmercury, then he misrepresents the study. Toxicity is all about dose. Ethylmercury is toxic to the brain, but it appears to be much less toxic than methylmercury. Further, ethylmercury is rapidly removed from the body and does not accumulate, which is very different from methylmercury. The reason to avoid eating fish with mercury is the concern that it will accumulate in the tissue. Small doses will therefore build up. This does not happen with ethylmercury, therefore tiny doses below the toxicity threshold are safe.

What does the study he is touting actually show? The researchers looked at the mechanisms of toxicity in ethylmercury and methylmercury (collectively called alkyl mercury) and found that there is some overlap in their mechanisms.

“This paper represents a summary of some of the studies regarding these mechanisms of action in order to facilitate the understanding of the many varied effects of alkylmercurials in the human body. The similarities in mechanisms of toxicity for MeHg and EtHg are presented and compared. The difference in manifested toxicity of MeHg and EtHg are likely the result of the differences in exposure, metabolism, and elimination from the body, rather than differences in mechanisms of action between the two.”

The mechanisms are similar, not identical. But, even if we take the extreme position that ethylmercury is as inherently toxic as methylmercury, the authors conclude from this that the actual difference in toxicity is therefore due to differences in metabolism and elimination – which was the CDC position all along.

In order to understand toxicity research you need to realize that a lot of the research involves directly exposing tissue in vitro to the chemical in question. If you directly drip alkyl mercury onto brain cells in a petri dish, it is very toxic. This does not necessarily mean, however, that exposure of an organism to the compound will have the same toxicity. Organisms evolved natural defenses against toxins. The substance may be rapidly metabolized or removed, or may never get to the target tissue in significant concentrations.

In this study the authors are not saying that ethylmercury is as toxic as methylmercury, as Kennedy falsely claims. They are only saying that both share similar mechanisms of toxicity, and therefore the very clear difference in toxicity that other research has established is likely due to other factors, such as the more rapid elimination of ethylmercury.

Kennedy’s article is an excellent example of distortion and propaganda. This is partly because he is an activist and not a scientist. The idea that Trump wants and extremist ideologue who can’t properly interpret a scientific study to head a commission on scientific integrity is extremely telling.