Measles Vaccine and Autism Link Disproved
In keeping with my back-to-school / vaccine theme at the start of September, I want to report on one more study investigating the safety of vaccines. According to CNN, the theory that there is a link between the measles vaccine and autism in children began in 1998, as the conclusions of a published study that suggested the vaccine caused gastrointestinal (GI) problems which then led to autism. The theory was disputed this past month by a new study, in a paper co-authored by one of the original paper's authors.
Researchers from Columbia University, New York, a laboratory of the Centers for Disease Control and Prevention, and the British laboratory where the original study was performed, analyzed samples from the GI tracts of children immunized with the measles vaccine. The original theory was that virus from the vaccine grew in the intestines causing inflammation and problems associated with leakage through the damaged, porous bowels. Their paper reports overwhelming evidence that the virus does not inhabit the intestines. The study has the support of several vaccine and infectious disease experts, including the vice president of scientific affairs for "Autism Speaks". However, critics of the study say it does not disprove any link between measles and the vaccine.
The issue of whether or not vaccines are safe has been the topic of intellectual debate and bioethical controversy for a decade now, and has resulted in the re-emergence of several previously-eradicated diseases in the United States due to parents who adopt the precautionary principle and opt out of vaccinating their children.
Sources:
CNN.com. September 3, 2008. Study: No link between measles vaccine and autism. http://www.cnn.com/2008/HEALTH/09/03/measles.autism/index.html
Hornig M, Briese T, Buie T, Bauman ML, Lauwers G, et al. 2008 Lack of Association between Measles Virus Vaccine and Autism with Enteropathy: A Case-Control Study. PLoS ONE 3(9): e3140 doi:10.1371/journal.pone.0003140
Comments
WHOA, hardly disproved! Read on:
“We were trying to find what he found,” Lipkin said.
Odd, then, that they didn’t look at the same type of kids.
A recent paper titled “Lack of association between measles virus vaccine and autism with enteropathy: a case-control study” by Hornig, et al.. (PLoS ONE. 2008 Sep 4;3(9):e3140) has been represented as the final word in the controversy about whether or not there’s a link between autism and the MMR vaccine. Curiously, the authors write, “Failure to replicate [Wakefield’s] original study design may contribute to continued public concern with respect to the safety of the measles, mumps, and rubella (MMR) vaccine.” They were referring to past MMR-autism studies, which looked for measles genetic material in the blood, as opposed to Wakefield’s tissue biopsies. It’s curious because in fact Hornig, et al. did take a step in the right direction—they looked at tissue biopsies—but the pretense that their study is a replication is just plain wrong.
In Wakefield’s 2002 study, researchers found measles in 75 of 91 biopsies from autistic children with GI inflammation, and in only 5 of 70 samples from non-autistic children (Uhlmann, et al. Mol Pathol. 2002 Apr;55(2):84-90). The children with autism in the 2002 study developed gastrointestinal symptoms and autistic regression after the MMR vaccine., Only 5 of the 25 children in the Hornig study group developed these symptoms after the MMR vaccine—all of the others showed symptoms of autism before vaccination; so only those five are fair to compare to the 2002 study. (This is like testing whether cell phones cause cancer by comparing 20 people who had cancer before they ever touched a cell phone to five people who developed cancer after owning one.) Anyway, common sense is enough to tell us that a study group of five isn’t large enough to reveal much of anything, no matter what’s being tested.
Notably, biopsies in Wakefield’s study were taken from the ileum, since this is the only site in the lower intestine where he had found evidence of measles virus protein in earlier studies. In contrast, Hornig’s biopsies came from the cecum (part of the colon) or the ileum, and we are given no indication of how many of the uniquely relevant ileal biopsies were actually used. (The discrepancy arises because some doctors find it difficult to get into the ileum and– as in this case– are left with having to settle for colonic biopsies.)
Both reflux symptoms and food allergy were other factors that emerged in the Hornig study group, but there was no mention of diarrhea or constipation, the two GI symptoms most common in the 2002 UK children. So the populations under consideration appear to be very different, a fact that the Hornig group apparently decided to ignore, or overlooked.
Paradoxically, Hornig’s study affirmed results from the laboratory of Professor John O’Leary (he’s one of the collaborators on the new study, and senior author of the 2002 study) as correct, and identical to results obtained by the other laboratories used in this new study (Centers for Disease Control and Prevention [the CDC] and Dr. Ian Lipkin of Columbia University), inadvertently validating the results obtained from lab work done in the earlier, Wakefield study.
Northeastern University Professor Richard Deth commented, “If gut inflammation persists after the virus is cleared, it is a sign that the inflammatory response has not been reversed (i.e., oxidative stress persists). In my view, this is the central issue in autism: persistent, unremitting oxidative stress, which can be triggered by different exposures. In other words, all children experience an inflammatory response to the MMR, which is part of why vaccination works. The response is normally mild and self-limiting, but children with redox and methylation vulnerabilities have a stronger inflammatory response that frequently does not turn off, yielding persistent oxidative stress.” In other words, there is a plausible connection between MMR and ongoing tissue damage.
This new study rules out just one thing: that the measles virus must remain active in the intestine for the long term for us to be able to say that it can cause the bowel disease that is associated with autism. The question remains, could the MMR vaccine cause autism in a one-time injury, without necessarily leaving evident measles virus behind? We don’t know. More research is needed. Parents of children who regressed after their MMR vaccine deserve a solid, irrefutable answer; sadly, by representing itself as the final word, the recent Hornig study decreases the chances that they’ll get one.
Well said Anne!
I’d like to hear a point-by-pointn rebuttle by the author, Theresa Phillips, to what Anne VR commented.
Anne,
You have made some very good points and obviously know more about the topic than I do. I’d like to start by saying it was my mistake to use the word “disproved” – any good scientist knows that nothing is proven or disproven as a result of one study, but that the evidence might “strongly support” one or another of opposing theories. My mistake (and the topic of today’s blog)! The point I really meant to get across was that in light of this study, it does appear that this particular connection linking autism and GI disturbances to MMR, VIA the presence of MV RNA in the intestines, may be incorrect. Of course, you have made comments to address this (see below) and of course there might be another route via which the three are still connected.
I will address your comments by paragraph:
P2: Good point but it DOES raise the question: what caused the autism and GI disturbances in Hornig’s other 20 subjects. You have addressed this in P6 and P7, and I agree.
P3: It appears to me, based on the M&M, that Hornig looked at both ileum and cecum samples from all the children tested although one could be more sure of that if they’d presented all the data, which I can’t seem to find. Table 3 only presents data on their positive PCR results, not the negatives.
P4: Again, you have made a valid observation. I wonder if the MMR caused the diarrhea or constipation but NOT the autism?
P5: Also true. What sends off alarms for me is the opening statements by the Hornig group that, since Wakefield, subsequent investigations have not been able to link MV exposure to ASD. Assuming these are the epidemiologic studies referred to in the introduction, regardless of where the virus RNA is found and how long it survives, how come 20 studies haven’t linked the vaccine to symptoms of the disorder?
P6 and 7: It’s a pleasure to get such well thought out comments from knowledgable people who are reading my blog. Thank you very much. It’s a tough site to maintain as I have to learn and write a lot about a variety of topics, and I am certainly not an expert in everything. My intent sometimes is to open a topic for discussion and I thank you for participating.