So here it is, already a week into 2015. Truth be told, I’m still finding myself having a hard time believing that it’s already 2015, but then I say that about every year in early January. Be that as it may, I’ve already seen one hopeful sign that it could be a decent year when it comes to science refuting claims of the antivaccine movement. In fact, there’s already been a study that once again fails to find even a hint of a whiff of a whisper of evidence for a link between vaccines and autism. It comes in the form of a study from Japan published online in Vaccine on January 3 (which, oddly enough, was a Saturday, but then there’s no reason to wait over the whole holiday weekend to publish evidence slapping down antivaccinationists) entitled Early exposure to the combined measles–mumps–rubella vaccine and thimerosal-containing vaccines and risk of autism spectrum disorder. It comes to us courtesy of Nagoya University, the Yokohama Psycho-Developmental Clinic, Fukushima University, and Juntendo University.
I realize that I’ve already given away the punchline, namely that this is yet another in a long line of studies that failed to find a link between vaccines (in particular the MMR) and autism or between thimerosal-containing vaccines and autism, but the journey to refuting antivaccine quackery with pseudoscience is more than half the pleasure. So let’s take a look.
One thing I liked about this paper off the bat is that it didn’t shy away from acknowledging the source of the idea that the MMR vaccine causes autism:
The view that vaccinations and ASD are related dates back to Wakefield et al.’s article ; however, the paper was retracted in 2010 because of ethical and methodological problems .
Unfortunately, authors couldn’t leave well enough alone and followed that up with:
Thereafter, other studies suggested a link between the measles–mumps–rubella vaccine (MMR) and ASD [8, 9], and concerns emerged that thimerosal (49.6% ethyl mercury by weight)included in other vaccines as a preservative might increase the ASD risk [10–12].
Unfortunately, references 8 and 9 were both Wakefield references again. Seriously, people, there’s never a need to cite a Wakefield reference unless it is to cite it for its bad science, because since he became enamored of the idea that the MMR vaccine causes “autistic enterocolitis” (a made up condition) and autism Wakefield has not to my knowledge published a single scientifically sound paper. Then, referring to papers claiming to support a link between the mercury-containing preservative thimerosal, which was in many childhood vaccines until 2002, the authors cite a Medical Hypothesis paper, which was not such a good idea. They then redeemed themselves by citing as references 11 and 12 a paper by Paul Offit discussing the manufactoversy over thimerosal and but then cited the 1999 Joint Statement of the American Academy of Pediatrics (AAP) and the United States Public Health Service on concerns about thimerosal. I suppose I should be happy they didn’t cite any of Mark and David Geier’s efforts at dumpster diving the VAERS database, as those papers are so bad that they should be never cited, except, of course, as examples of every error in epidemiology that can be made.
But enough of my pet peeves. The authors then went on to discuss the studies that didn’t find a link between either MMR vaccination and autism or between thimerosal-containing vaccines and autism. So why did they bother to do a new study? Their rationale is actually kind of interesting, but I’m not sure it was compelling enough to warrant a new study:
However, most studies have not considered vaccinations timing and the subject’s racial heterogeneity even thoughgenetic factors are known to be strongly involved in ASD onset. Asan investigation that specified the race of the study participants,we conducted a case–control study from the Japanese population . Japanese people were proven to be highly genetically homogenous according to the genotyping results of 140,387 single nucleotide polymorphisms . In our previous study, there was not any convincing evidence that MMR vaccination was associated with an increased risk of ASD in Japanese people. However,the effects due to the differences in vaccinations timing and theamount of exposure to thimerosal were not accounted for in this study.
OK, fair enough. The Japanese are a pretty genetically homogeneous people compared to most other areas where the question of whether vaccines cause autism has been studied, but, given the multiple resoundingly negative studies done before, it’s highly unlikely that doing it again in the Japanese would provide a different result, and it didn’t. Don’t get me wrong. This is a good study. I just detest how good scientists are forced to partially buy into antivaccine tropes, such as the claim that there are “genetic triggers” that make some people more susceptible to “vaccine-induced autism” given that, despite many studies looking for increased prevalence of autism associated with vaccination or thimerosal in vaccines.
Enough of my grousing about the introduction. What about the study itself? It’s a case-control study, which means looking at vaccine history in autism cases versus controls after controlling for known confounders and determining if there are differences in MMR vaccination or thimerosal exposure. Basically, vaccination histories at 1, 3, 6, 12, 18, 24, and 36 months from birth were investigated in ASD cases (189 samples) and controls (224 samples) matching age and sex in each case. Crude odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Then dosages of MMR vaccine and thimerosal were examined and investigated using a conditional multiple regression model in order to determine if there were is any relationship between autism and overall exposure. The population providing case data came from the Yokohama Psycho-Developmental Clinic (YPDC), a clinic that only accepts patients with suspected neurodevelopmental disorders. Eligible case subjects were evaluated by the YPDC between April 1997 and March 2011 and were (1) diagnosed with autism spectrum disorder and (2) had been born between April 1, 1986 and April 30, 1992.
There’s also a quirk in how the cases were chosen based on the unique situation in Japan.
MMR vaccination in Japan was conducted under specific circumstances and for only a short period of time. A combined MMR vaccination program commenced from April 1989, and only one vaccination using MMR was included in the immunization schedule. The monovalent mumps, measles, and rubella vaccines remained the optimal choice of vaccine for those who did not participate in the MMR program. However, soon after the immunization program had started, there were several cases of aseptic meningitis, which may have been caused by the mumps vaccine . As a result, in April 1993, the Government ceased extensive inoculation with MMR. Therefore, children who were born from April 1984 to April 1992 could receive MMR vaccination. However, children who were born between April 1984 and March 1986 were able to receive it after the age of three. Therefore, they were excluded from the samples, because autism features always appear before the age of three. As a result, children who were born from April 1986 to April 1992 were included in the present study.
These days, Japan still vaccinates against measles, but, because it was the mumps component of the MMR vaccine used in Japan, the Japanese now require a combined measles-rubella (MR) vaccine instead, which is mandatory, while the mumps component is voluntary but recommended. Of course, it’s hard not to note that autism rates continued to rise in Japan even after the discontinuation of the use of MMR combined vaccine and substitution with two separate vaccines that, together, cover the same diseases. Same as it ever was. Vaccines don’t cause autism; so it should not be surprising that stopping a vaccine demonized as the cause of autism does not result in a decline in autism prevalence.
In any case, the control group consisted of age- and sex-matched subjects recruited as volunteers from general schools in the Kanto area, which is the same area where YPDC patients live. Students who had previously been diagnosed with developmental disorders or problems were excluded.
So what were the results? I already told you, but it’s worth quoting the study:
There were no significant differences in MMR vaccination and thimerosal dosage between cases and controls at any age. Furthermore, the ORs (95% CIs) of MMR vaccination and thimerosal dosage associated with ASD in the conditional multiple regression model were, respectively, 0.875 (0.345–2.222)and 1.205 (0.862–1.683) at age 18 months, 0.724 (0.421–1.243) and 1.343 (0.997–1.808) at 24 months, and 1.040 (0.648–1.668) and 0.844 (0.632–1.128) at 36 months. Thus, there were no significant differences.
The authors thus quite properly concluded that there was no convincing evidence that MMR vaccination or increasing thimerosal dose are associated with an increased risk of ASD onset. Once again, there was not a whiff of a whisper of a hint of elevated MMR or thimerosal exposure in the case group compared to controls. A key strength of this study is that parents of children receive a document referred to as the Maternal and Child Health (MCH) handbook, which is described by the authors as a “highly reliable data record of early development, health, and immunization, and the data are recorded by health professionals (e.g., public healthnurses, obstetricians, and pediatricians).” This allowed the investigators to access detailed, accurate immunization records for cases and controls, and they excluded subjects in which entries regarding vaccines in the MCH handbook were missing or illegible. This allowed not only accurate assessment of the number of MMR vaccines each subject received as well as the total dose of thimerosal received by each subject.
So once again, a year starts out with researchers asking the questions:
Is MMR vaccination associated with an increased risk of autism?
Is thimerosal exposure in vaccines associated with an increased risk of autism?
Again, the answers to these questions are no and no. Vaccines do not cause autism. Again. Happy New Year!
In fact, so common is this finding now that I didn’t see a single news story about this study. That’s rather unfortunate, because I believe that it helps to publicize such studies, as yet another example of the depth and breadth of the evidence that has failed to find a link between vaccines and autism. One thing’s for sure. We won’t see this study mentioned on Age of Autism or any of the wretched hives of antivaccine scum and quackery promoting the scientifically discredited notion that vaccines cause autism, except perhaps to raise spurious criticisms of it and ask for more study.
Same as it ever was.