December 06, 2018

Primate Vaccination’s Impact on Gut Flora

A recent study published in Nature investigated the gut flora of infant macaques vaccinated with different vaccine schedules.  The text of “Microbial structure and function in infant and juvenile rhesus macaques are primarily affected by age, not vaccination status” is available at this link:
However, the usefulness of this study in assessing the gut microbiome as it relates to vaccination impacts on children with autism is limited as outlined in the review below by Children’s Health Defense board member, Dr. Brian Hooker.


Critique by Brian Hooker, Ph.D.

Hasegawa et al.,2018

This particular study was focused on the intestinal microbiome of infant and juvenile macaques who were exposed to either the 1990s or the 2008 vaccination schedule, including thimerosal-containing vaccines.  Unfortunately, this study contributes nothing in terms of understanding intestinal health differences in vaccinated versus unvaccinated children.

First, the sample size of each group was insufficient to develop clear differences in the gut microbiome for the different vaccinated and unvaccinated groups.  The experimental groups (receiving either the 1900s vaccination schedule or the 2008 vaccination schedule) consisted of just 12 animals each and the control group (receiving no vaccines) consisted of just 16 animals.  To pick up a “signal” for a gut microbiome presumably for autism, which has a prevalence of approximately 1 in 36 children in the U.S., each group would need at least 36 subjects.  Thus, this study was woefully “under-powered” to find such a signal and it would be rare that with these small groups, such a microbiome would exist.  It is therefore logical that there would be no differences in the microbial community among the different groups studied.

Second, the indicators of “gut health” were insufficient to assess a condition that could be consistent with autistic intestinal dysbiosis.  The study authors merely looked at the structure of the gut microbial community at the genus level using genetic probes targeted at 16S rRNA sequences (i.e., a genetic signature for the type of bacteria that exist in the macaque’s feces).  The method used was not quantitative; thus the relative abundance of microorganism species, relative to each other was never assessed.  The authors do call out different genera and families of bacteria typical to the gut but no attempt was made to correlate these to overall intestinal health.  To get any quantitative information on microbial species, one needs to run what is called a GI panel, which is the gold standard at identifying gut dysbiosis via microbial species that are problematic, for example, clostridium bacteria or candida yeast.  This was not completed on any of the groups of macaques.

Other intestinal markers that would be helpful include parameters of intestinal immune function including total secretory antibody lining the gut mucosa, lysozyme and chymotrypsin enzymes which may be present in quantities to fight intestinal pathogens.  These tests were simply not done, leaving a very limited snapshot of some bacteria and other organisms that may be present in significant quantities in the gut.  Again, this does not give any type of picture of overall intestinal health, especially conditions associated with neurodevelopmental disorders including autism.

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