A new article published by scientists for the Centers for Disease Control and Prevention (CDC) has been flagged by anti-vaccine advocates for being proof that vaccines are linked to sudden infant death syndrome (SIDS). A look at this study, and how it has been misinterpreted, can help underline the need for a better understanding of scientific methodology.
VAERS: A Lesson in Causation
The US Vaccine Adverse Event Reporting System (VAERS) was set up and managed by the CDC and the Food and Drug Administration (FDA). It was a consumer protection initiative designed to detect possible unknown risks of vaccinating. The purpose of VAERS is for individuals to report what they suspect to be adverse effects after receiving vaccination.
Scientists working for the CDC published a paper in an attempt to analyze VAERS reports over a 23-year-period from 1990-2013, specifically for the Haemophilus influenzae type b (Hib) vaccine. Out of the 29, 747 reports, 896 of them resulted in death. Of the 896 deaths, only 749 of them had certifiable records. Out of the 749 cases of certified deaths only 384 (51%)were caused by SIDS. It is this 51% figure that has been touted by the anti-vaccine movement to be proof that vaccines cause SIDS.
Anti-vaccine website GreenMedInfo, ran with the headline, “CDC’s Own Data: Vaccine-Infant Death Link”. The subtitle of the article makes a stronger declaration about vaccines and SIDS, claiming that the, “link is real”. Sayer Ji, founder of GreenMedInfo, begins his article by pointing out that the CDC and the FDA think vaccines are safe. However, he suggests that these governments did so “a priori”, or in more colloquial terms, before they had any evidence. This new study, he points out, seems to contradict what these government organizations have been saying all along!
In what way does VAERS allow us, or research scientists, to make any conclusions about possible links (real or not) between vaccines and adverse reactions? Links come in degrees. When I eat lunch, the church bell by my house begins to chime twelve times. In some sense, these two activities are linked; noon happens to be when I normally eat lunch. They are not causally linked though, the ringing didn’t cause me to begin eating, I would have ate regardless of the bells ringing. My hunger is causally linked to me eating, but the bells, in some sense, are only superficially related to my eating. This is the scientific issue involving correlation and causation. Research scientists in the field of medicine are interested in correlation, but only as a tool to indicate further research. If I swallow something and then the next day my flu disappears, that is interesting, and may indicate that we should see whether or not it was in fact the thing I swallowed that made my flu disappear. Correlation is a link, an important link, but it isn’t as real a link as a causal link. This is why you always hear scientists and skeptics claiming that correlation does not equal causation. You cannot make claims about a causal relationship based merely on a correlation.
There are several limitations to reporting data bases that make them poor tools for finding “real” or causal links:
1. Unverified Reports: It is not the job of VAERS to follow up on every detail, about every report, not to mention funding issues that would make that impractical. It is also not the job of VAERS to make causal claims, so the fact that these reports are unverified does not matter. The purpose is to indicate possible signals for further investigation, not to make claims about actual relationships between vaccines and adverse effects.
2. Underreporting/Overreporting: VAERS is not actively trying to seek out adverse effects, it is a reporting system. This means that if vaccines were actually causally linked to something, not everyone who had a reaction would report it. This could happen because people don’t know that VAERS exists, or that they didn’t know that what harmed their child was actually related to the vaccine. Furthermore, given the fears raised by the anti-vaccine movement about SIDS or any other illnesses they suspect to be caused by vaccines, could lead to overreporting as people begin to link everything that happens to their children to vaccines.
3. Inconsistent Data Quality: It was found that most of the cases in the VAERS database reporting a relationship between vaccines and autism, were called in not by parents, but by personal-injury lawyers (you can find more information about this in Dr. Paul Offit’s wonderful book, Autism’s False Prophets). It should be obvious that this is a conflict of interest. Lawyers who stand to profit off of a link between vaccines and adverse effects, report these claims to VAERS and then use VAERS in court to claim that vaccines are bad. As Dr. Offit explains, “For the lawyers, VAERS reports hadn’t been a self-fulfilling prophecy; they’d been a self-generated prophecy”.This points to the larger issue that not all reports recorded by VAERS have the quality necessary to be able to make claims about causation.
4. Lack of Controls: In order to make a causal link between something, you need one or more control groups. How can you conclude that there is a link between vaccines and SIDS if you don’t know the rate of SIDS in those who do not vaccinate? Even if you do that comparison, and you find a relationship, it still does not mean that vaccinations caused SIDS (although it may increase the probability). It is possible that those who vaccinate live different lifestyles, and engage in different behaviours, than those who do not vaccinate. More work needs to be done to rule out other possible confounding variables.
Out of all of these possible limitations, the only one that was raised by Ji in his article was underreporting. Which is convenient, since it is the only limitation which would make the possible link between vaccines and SIDS look worse if true.
Ji finishes his post by claiming that the CDC scientists are “callous” for concluding, “Review of VAERS reports did not identify any new or unexpected safety concerns for Hib vaccines”. Aside from the limitations of VAERS, science is not an isolated process. Several studies have been done on this supposed link between vaccines and SIDS all of which found nothing. Here and here for example. The second study, which was a meta-analysis, found that those who do not vaccinate had a higher incidence of SIDS than those who do vaccinate. This might not have anything to do with the vaccines themselves, but is pretty strong epidemiological evidence that vaccinating your kid actually lowers, rather than increases their risk for SIDS. So, were the CDC scientists really “callous” for their conclusion or is Ji just desperate for any evidence, no matter how weak, to reinforce his ideological position against vaccines?
The Evil CDC
I was in the middle of writing this weeks post on the psychological underpinnings of conspiracy ideation, when I realized it was going to require more research than I had time for this week. So, I opted to write about anti-vaccine stupidity instead (but stay tuned for that piece soon!). In relation to the psychological effects of conspiracy ideation, I find it incredibly interesting that those who accept conspiracy theories against large government agencies, such as the CDC and FDA, will accept data from them so long as it supports their own position. If the CDC is really a corrupt body, which hides the evidence against vaccines, merely so they can earn that vaccine money, all the while allowing other people to suffer, would they really be so stupid to release information that would expose themselves? If the anti-vaccine movement is right, and this conspiracy exists, the CDC would have to be a highly-intelligent, well-orchestrated and highly-monitored group. Which flies in the face of their portrayal by the anti-vaccine movement, as a bunch of bumbling idiots who expose data that vaccines are bad all the while twiddling their thumbs claiming, “Move along! Nothing to see here!”. This is the biggest problem about conspiracy ideation, that all evidence can be filtered and twisted in order to show that the conspiracy is true. No evidence at all is evidence of the conspiracy, and evidence against the conspiracy is actually evidence for it. In other words, you have completely walled yourself off from reality.
Vaccinate your kid already.