I recently attended a talk where the speaker showed autism prevalence by age group for a large HMO in California. The administrative prevalence (fraction of people in the HMO identified autistic) was still going up as of 2010, and the speaker indicated this trend continued to 2012. California is an interesting case study because not only was thimerosal removed from vaccines along with the rest of the U.S. starting in the late 1990′s, but the state enacted a law which required that pregnant women and children under three be given thimerosal free vaccines from 2006 onward. So, with the exception of an an exemption in 2009 and another one right now, even the influenza vaccine in thimerosal free. I bring this up because it is a common argument that somehow the exposure from the flu vaccine is keeping the rate climbing, even though at most this is a lower exposure than that from the 1990′s pediatric vaccine schedule.
This all said, the talk made me dive back into looking at autism prevalence. I decided to finally write about the fact that the autism prevalence in Denmark is higher post thimerosal than while thimerosal containing vaccines were in use. This is completely unsurprising, but a myth has been propogating that it came down and that fact was being hidden.
As it turns out I also checked back with what once was the most common source of autism data for the armchair epidemiologist: the California Department of Developmental Services (CDDS). (I admit one could argue that Special Education data are the most common source for the armchair epidemiologist). The CDDS provides services to disabled Californians and keeps and makes public statistics on their client base. For a long time, every quarter they would come out with a report. For a long time, every quarter these reports would be followed by announcements about how the data showed that vaccines cause autism. One of the people you could always count on was David Kirby (author of the book, Evidence of Harm: Mercury in Vaccines and the Autism Epidemic: A Medical Controversy, and basically a PR man for some of the vaccine-causation groups). Mr. Kirby went so far as to claim that these data were the “gold standard of autism epidemiology”. Well, the data had their uses (such as identifying and quantifying some of the social influences behind the increase) but it is not an easy task to get results from them. The idea that they represent an accurate count of all those with ASD’s (or even accurately account for all individuals with autistic disorder) is a stretch.
But this didn’t stop David Kirby. Back in 2005, David Kirby was claiming that there was an indication that the administrative prevalence in California was starting to drop, and if the trend continued this was a sign that the removal of thimerosal was having an effect:
Well, by 2007 it was clear that the California data were not really showing a drop. In addition, the lack of a drop was published in 2008 as Continuing increases in autism reported to California’s developmental services system: mercury in retrograde.\
The rise in the number of autism clients in the CDDS database was key to the idea of the mercury-induced epidemic. David Kirby (and others) relied on these data and Mr. Kirby even acknowledged that the data should start showing a drop (statement from 2005):
If the total number of 3-5 year olds in the California DDS system has not declined by 2007, that would deal a severe blow to the autism-thimerosal hypothesis.
The reason is that 5 year olds in 2007 were born after the removal of thimerosal from vaccines. Their exposure to thimerosal was much less than kids in the 1990′s. If the “thimerosal caused an autism epidemic” idea were true, the rates would have to drop. They should drop back to pre-1990 (actually pre 1980) levels if thimerosal were the main, or even a main, cause of the rise.
My recollection is that Mr. Kirby did later backpedal and claim that we would have to wait until some much later date, but it was a weak argument (even by David Kirby standards).
Sorry to keep diving into past history, but one of the strangest moments in the mecury debate (and I can use the term this time, because there was a debate) came in San Diego in 2007. David Kirby debated Arthur Allen in the UCSD Price Center (about 100 yards from my old office, as it turns out). Presented with the fact that even though thimerosal exposure from vaccines had gone down, the California numbers kept going up, David Kirby presented (in something like 100 power point slides!) a four pronged response. First was a claim that California HMO’s had stockpiled thimerosal containing vaccines, so the exposure from vaccines didn’t really go down as much as reports were claiming. Then:
1) A gigantic plume of coal smoke from Chinese power plants has settled on California, depositing lots of mercury and therefore causing the autism numbers in the state to continue to grow.
2) Bad forest fires have put tons of mercury into the air, depositing lots of mercury etc…
3) Cremations (!). The burning of dead bodies with mercury amalgam in their mouths has added even more mercury to the air.
It was a hail Mary pass, to be blunt. Lot’s of handwaving and ignoring the facts.
In 2007, the CDDS changed the way they assessed and counted their clients and they stopped publishing the quarterly reports. As you can imagine, many claimed this was part of a conspiracy to hide the fact that the autism rates were declining in California. And with that the quarterly ritual of misinterpreting and deconstrucing the data came to an end.
All amusing history, sure, but one might ask, why bring all this up again? Well, because it turns out that the CDDS started putting out quarterly reports again in 2011. Yes, there’s a gap of a few years in the data. Yes, some things changed (for example, the CDDS now shows the PDD fraction of autism client base). Given these limitations–and the other limitations in the CDDS data (i.e. they are *not* the “gold standard” of autism epidemiology), what do these data show? The upward trends continue. More individuals served by the CDDS with autism, even though thimerosal was removed from vaccines. Here’s the total–all ages–count for CDDS clients in the autism category (click to enlarge):
Looking at the younger age groups, those whose exposure to thimerosal is much lower than for kids born in the 1990s, there is also an increase. Here is the age 3-5 age group (click to enlarge)
and the 6-9 age group (click to enlarge):
9 year olds in 2012 were born in 2003. Post the removal of thimerosal nationwide. 5 year olds were born in 2007, post thimerosal nationwide and post the California law prohibiting mercury in vaccines for pregnant women and small children. In both groups, the CDDS autism counts are higher than they were in 2002 (the earliest date in the currently available data). Which, in turn, was much higher than the counts from the 1990′s. Here is a figure from the Schechter-Grether paper refenced above:
Which is all a very long way of saying: years ago the evidence was against the thimerosal/epidemic idea; it is even more clear now. For years we heard Mr. Kirby and others talk about how those responsible should step up and admit what happened. Well, the fact is they did. Now it is time for those who promoted the mercury notion to step forward and show they have the guts to admit they were wrong. Because they were. Clearly wrong. It would take a lot of guts to step forward and admit the mistakes. Even though their influence has waned, it would help the autism communities. While I have focused on David Kirby in this discussion, the list is much longer of people who should step forward. I’m not going to hold my breath.
By Matt Carey