Monday, May 6, 2013

MIND Institute: No Difference in Immunization Rates

There are a lot of studies on vaccines and autism. The majority (read: the ones that are well-designed to minimize the influence of biases and confounders) show that there is no connection between vaccines and autism. Or, rather, I suppose I should use a more scientific turn of phrase: they have failed to find any causal connection between the two. There are some rather bad studies (small sample sizes, methodological flaws, etc.) that anti-vaccine activists like to crow about, like a horribly flawed macaque study that should never have been approved by an IACUC (IACUCs are institutional ethics boards that review studies using animals) in which there were not enough controls, missing conflict of interest statements, missing authors, and so on. In short, it put a bunch of macaques through needless procedures and death for no reason.

Of course, the anti-vaccine folk invariably pooh-pooh the rigorous studies, saying that they are horribly tainted and unreliable, the authors in thrall to Big PharmaTM. As they rationalize away any study that doesn't agree with their near-religious adherence to their preconceived notion that vaccines are the most evilest of all evilosity, they call for "independent" research looking at vaccines and autism. However, finding what they consider to be independent researchers is a bit dicey. Funded by NIH or equivalent governmental agencies? Nope. After all, government is in league with Big PharmaTM, dontcha know. Universities? Doubtful, since a lot of universities receive grants from corporate foundations. It doesn't matter that the researchers don't actually see any of that money, of course. The merest hint of a whiff of a connection is enough for them to dismiss anything that doesn't agree with their ideology. Is there any organization that they'll trust that actually has qualified researchers who don't stand to gain from finding a vaccine-autism connection?

Well, they might be okay with the University of California-Davis MIND Institute.

The MIND Institute was established in 1998 by families dealing with autism. They wanted to establish a place where a multidisciplinary team of experts could come together to discover more about neurodevelopmental disorders and how to improve the futures of those affected by them. Sounds like a place that the folks at, say, Age of Autism could get behind. Certainly, they have spoken favorably of them in the past. Then again, when a study comes out that doesn't address vaccines or that points to something other than vaccines as a cause of autism, they have a tendency to complain about the findings.

Well, at the recent International Meeting for Autism Research (IMFAR), held this past weekend, May 2-4, at the Kursaal Convention Center in Donostia / San SebastiĆ”n, Spain, the MIND Institute presented a new paper looking at vaccines and autism. After reading the extract, though, I got the sneaking suspicion that the hardcore "Vaccines did it!" crew won't particularly like it. Why not? Well, just take a look at the title: No Differences in Early Immunization Rates Among Children with Typical Development and Autism Spectrum Disorders.

Led by Dr. Kathleen Angkustsiri, the MIND researchers examined the immunization records of 240 preschoolers (161 with an autism spectrum disorder [ASD], 79 with typical development [TD]) aged 2 to 4½ years old. The aim was to compare immunization practices between the two groups to see if there was any relationship between vaccines and ASDs. Angkustsiri et al. compared the rates based on the California School Immunization Requirements (PDF) for ages 18 months to 5 years. Overall, for both groups, vaccine uptake was around the same as or slightly higher than the rates in the 2011 National Immunization Survey. But how did they compare to each other? One would expect that if vaccines really did cause autism, then, based on the idea of dose-response (i.e., the higher the dose, the greater the likelihood of a certain response), we would probably see a greater number of vaccinations among the ASD group.

It turns out that the ASD group's rates were actually slightly lower than among the TD group, though this difference did not reach statistical significance. In other words, rates for both groups were about the same, within the statistical noise, with the exception of one vaccine: Hep B. For this vaccine, which is often the target of much criticism ("Why do babies need to be vaccinated against a sexual disease?", forgetting the fact that the virus can survive in the environment for about a week, leaving non-sexual means of transmission open), the uptake among ASD subjects was significantly lower than among the TD subjects, 91.3% compared to 98.7% (p=0.024), respectively. If we were to use the anti-vaccine mode of thinking, we could argue that this means Hep B is protective, reducing the risk of an ASD. But, we actually stick to the science, so all we can say is that this is an interesting observation that suggests that Hep B vaccine is not implicated as a cause of autism. Also of interest, there was only one subject who was completely unvaccinated. That subject was in the ASD group.

What does this mean for the vaccines-cause-autism manufactroversy? Well, the authors note that, "although not designed to specifically address a causal relationship, [our study] does not support an association between vaccines and ASD". It certainly does not bolster anti-vaccine activists' claims. Rather, it is yet another study casting doubt on their mistaken belief.

There are a few objections that I can see folks like those at Age of Autism leveling against this study. First and foremost, of course, there will likely be someone making hay about the fact that it did not compare vaccinated vs. unvaccinated. Like the criticisms about the DeStefano antigen-exposure study (PDF), this misses the point of the study. Angkustsiri et al. were not looking at vaccine uptake to see what the outcomes were. They were looking at the outcomes to see if there was any difference in exposure.

Another complaint that might be levied at this study is that vaccine uptake rates in the ASD group may be lower because those families with ASD may be more likely to refuse vaccines, either because an older sibling had a diagnosis of ASD or vaccinations stopped after the subject was diagnosed. This doesn't seem to be the case, though, given the similarity in uptake between the two groups. It's hard to say, though, just from the abstract. I'd like to see the full study text to see if they address this issue, though the abstract does hint that the authors took this into account:
In most cases, these immunization practices represent behavior during the first 18 months of life prior to receiving an ASD diagnosis. Further study looking at differences in vaccine acceptance during the 4-6 year booster period is warranted, as having an ASD diagnosis may affect parents’ attitudes towards future immunization.
A final complaint I foresee is that the study doesn't address possible genetic predispositions to supposed "vaccine injury". Critics may argue that despite receiving generally the same number of vaccines, those with ASDs were simply susceptible to injury. The authors admit that the study was not designed to detect a causal connection. Instead, it just looked to see if there was any difference in immunization rates between those who had a diagnosis of an autism spectrum disorder and those who did not. Like the antigen study, this one suggests that the "too many, too soon" argument probably does not hold any water.

All in all, the study appears to be well-designed. It used a moderately sized subject pool, confirmed diagnoses, immunization records rather than parental recall, etc. An added bonus is that it comes from an institution that is generally decently regarded by anti-vaccine organizations, so it will be interesting to see how they go about trying to discount it. Add another study to the pile showing no causal connection between vaccines and autism.

Hat tip to Matt Carey at Left Brain/Right Brain.

No comments:

Post a Comment

You need a Google, LiveJournal, WordPress, TypePad, AIM or OpenID account to comment. If you need one of those, click on the appropriate link.