SafeMinds is an organization which has long promoted the idea that thimerosal caused an autism epidemic. They may be the single greatest force that got the idea into the public’s eye, and got research funding focused on looking at the question.
SafeMinds has shown themselves to be very resistant to the very research they called for. Studies which show a lack of association between thimerosal containing vaccines (TCV’s) and autism are always rejected by SafeMinds. They are not alone in this, groups such as Generation Rescue and the National Autism Association (NAA) have also refused to accept the science.
So it was with no surprise that I read that SafeMinds had issued a statement against the study. The statement starts by pointing out that the study was funded and performed by those with conflicts–the CDC, Abt (an organization which does contract research for groups including the CDC), and HMO’s “which receive substantial funding from vaccine manufacturers to conduct vaccine licensing research”.
If we can’t use the HMO’s to work on such project, that sort of takes away the VSD as a tool. It certainly takes away the opportunity to do anything more than passive surveillance of the VSD data. One of the strengths of the Price study was the effort to do more than just review the medical charts. They worked with the children, both cases and controls, to verify that the autism counts were accurate. I bring this up because groups like SafeMinds frequently request access to VSD data.
SafeMinds also discusses the study methodology:
The study sample did not allow an examination of an exposed versus an unexposed group, or even a high versus a low exposed group, but rather the study mostly examined the effect of timing of exposure on autism rates.
There is much wrong with the above statement. Let’s start with where they are close to correct. The study sample did not allow for a direct comparison (with good statistics) of exposed vs. unexposed. This is true. This is because there are few unexposed kids (unexposed=no thimerosal exposure in this study. Unexposed does not mean no vaccines). If you look at exhibit 9.1.4 from the technical reports by Abt associates (the detailed reports on the study), you will see about 20-30 “unexposed” children. I.e. children with no thimerosal exposure. Of those, about 3-4 (out of 1,000) had no HiB, HepB or DTP vaccine vaccine at all (MMR isn’t listed as it is not a source of thimerosal). This is in line with estimates by the CDC of how many children are unvaccinated (typically about 0.4%). (as an aside–this points out how difficult it would be to do a good study of vaccinated vs. unvaccinated children using the VSD. Seriously, with 99.6% of kids receiving at least one vaccine, you would need a huge number of kids to get the number of unvaccinated needed for good statistics).
Here is that exhibit, with the no-exposure kids circled. (click to enlarge)
It would appear to this reader that the issue of unexposed vs. exposed isn’t so much one of “study design” as the limitations of the VSD itself. There just aren’t that many autistic kids to make a good statistical comparison of unexposed vs. exposed populations.
And, it should be noted, an unexposed vs. exposed comparison wasn’t the purpose of this study. One big question posed by SafeMinds and later picked up by groups such as Generation Rescue was simple: did the increase in thimerosal exposure from vaccines in the 1990’s result in an “epidemic” of autism? This is the question this study addressed.
I am at a loss as to why SafeMinds wrote this: “….or even a high versus a low exposed group, but rather the study mostly examined the effect of timing of exposure on autism rates”. Contrary to SafeMinds’ assertion, there is a large variation on thimerosal exposure in the study subjects. One of the surprising facts from this study was the number of children receiving thimerosal-free vaccines. This, together with variations in the number of vaccines administered, led to a much larger distribution in thimerosal exposures than one would expect based on the vaccine schedule alone.
Thus, the study was not on “timing” at all. It was, as advertised, on variation of exposure of thimerosal. The question is (at least to me), does the range of exposure amount to significant number of kids having “low” levels of exposure by SafeMinds’ definition?
The answer, it turns out, is yes.
[Autism] remained rare (1 in 10,000) until the rapid escalation of vaccines beginning in the late 1980’s (from 10 shots of 7 antigens in 1983 to 36 shots of 15 antigens). Vaccines are a likely candidate to explain some, if not most of the rise in autism cases and possibly other chronic childhood disorders linked to immune system malfunction.
In one of the seminal papers on the thimerosal was co-written by SafeMinds founder Lyn Redwood Autism: a novel form of mercury
poisoning. In it, the authors state:
The discovery and rise in prevalence of ASD mirrors the introduction and spread of TMS in vaccines. Autism was first described in 1943 among children born in the 1930s (123). Thimerosal was first introduced into vaccines in the 1930s (7). In studies conducted prior to 1970, autism prevalence was estimated, at 1 in 2000; in studies from 1970 to 1990 it averaged 1 in 1000 (124). This was a period of increased vaccination rates of the TMS containing DPT vaccines among children in the developed world. In the early 1990s, the prevalence of autism was found to be 1 in 500 (125), and in 2000 the CDC found 1 in 150 children affected in one community, which was consistent with reports from other areas in the country (126). In the late 1980s and early 1990s, two new TMS vaccines, the HIB and Hepatitis B, were added to the recommended schedule (7).
I know I am spending a lot of time on this point, but it is important. The idea that there is a dose-response relationship between thimerosal and the presumed risk of autism is fundamental to the arguments made by groups like SafeMinds.
A sister organization to SafeMinds, Generation Rescue, says the same thing. In their take, “This is the schedule from 1983. If it worked for kids then, why doesn’t it work for kids now?”. Generation Rescue leader and spokesperson Jenny McCarthy wrote in her book, Healing and Preventing Autism: A Complete Guide, “In 1983, we had 10 shots on the vaccine schedule and autism was one in 10,000. Today there are 36 given and autism is nearing one in 100″. I.e. if we go back to the 1983 vaccine schedule, autism rates should drop to 1 in 10,000.
The 1983 schedule, as graphically presented in expensive full page newspaper ads by Generation Rescue, included 4 DPT shots (yes, the old whole cell pertussis vaccine). Each of those shots included 25 micrograms of mercury.
It strikes this reader that the thimerosal exposure from 4 DPT shots, the amount in the 1983 schedule that supposedly only resulted in 1 in 10,000 kids having autism, should be a “low” exposure amount. If groups are going to point to 1983 as a safer schedule and point to the increases in thimerosal exposure in the 1990’s as the major sign of the “epidemic”, we should be able to take their word that the levels in 1983 were somehow safer.
Let’s look at that figure from the Price study again, shall we? I will highlight how many kids have “low exposure” (i.e. comparable to the 1983 vaccine schedule) to thimerosal. Again, click to enlarge if you wish.
By my eye, something approaching 50% of the kids in the study received the thimerosal exposure of the 1983 schedule. Certainly more than 25%. Those highlighted in red have the same thimerosal exposure as kids did in 1983, so they should have the same autism prevalence that SafeMinds and Generation Rescue claim for that time period: 1 in 10,000.
If that group has a prevalence of 1 in 10,000–or even anything significantly lower than the prevalence of those with higher thimerosal exposure– this study would have found it.
In other words, a thimerosal-induced epidemic of autism didn’t happen. Even using the logic that SafeMinds used to hypothesize it in the first place:that, somehow, the thimerosal exposures in 1983 resulted in a low autism prevalence.
Yes, this is far from rigorous. But, so is the logic that claims that increased thimerosal exposure led to an autism epidemic.
If we read further into the SafeMinds response, we see some of the confusion:
The study sample did not allow an examination of an exposed versus an unexposed group, or even a high versus a low exposed group, but rather the study mostly examined the effect of timing of exposure on autism rates. There were virtually no subjects who were unvaccinated and few who were truly less vaccinated; rather, the low exposed group was mostly just late relative to the higher exposed group, ie, those vaccinating on time.
SafeMinds seems to be assuming this is a study on the number of vaccines, not the amount of thimerosal. They also don’t appear to have read the study thoroughly enough to note that, yes, there is a large fraction who were “less vaccinated” and, more importantly to this study, a large fraction who had lower thimerosal exposures. As noted above, the low thimerosal exposures result from the fact that many of the children received thimerosal free vaccines.
It is unfortunate that SafeMinds (and other groups like them) can not adapt to science as it comes out. Science which clearly shows that many of their hypotheses were wrong.