Friday, 29 March 2013

Antigen content exposure and autism: no link

I'm hopefully not setting myself up for a fall by discussing the study published by Frank DeStefano and colleagues* (open-access) suggesting no link between the 'too many too soon' argument of vaccination and risk of autism. As probably would be expected with such study results, there has been a flurry of interest on this paper (see here and here for example) and so once again I'm not going to add too much to the details which have already been reported.

The basics:

  • Based on a final comparison of 256 children diagnosed with an autism spectrum disorder (ASD) with an asymptomatic control group of 752 children (all born between 1994 -1999), vaccination histories were examined and exposure to "total antibody-stimulating proteins and polysaccharides from vaccines was determined by summing the antigen content of each vaccine received". 
  • For those like me, who are not too well-versed in the immunological principles of vaccination, the antibody-stimulating proteins and polysaccharides bit basically refers to the constituents of vaccines designed to invoke an immune response and the production of antibodies to recognise and fight the bacteria/virus being vaccinated against. Quite by coincidence, the BBC recently carried an interesting article about new vaccines potentially coming from some analysis on the UK synchrotron, the Diamond Light Source (see here - click on the interactive video) which quite neatly sums up the hows and whys of vaccination. 
  • The study produced odds ratios (ORs) for ASD 'outcomes' during the first 2-years and found no evidence for any increased risk of autism based on antigen exposure. 
  • Bearing in mind quite a few other potentially interfering variables were also collected (maternal exposures, child birth conditions, etc.), the results similarly suggested "no associations when exposures were evaluated as cumulative exposure from birth to 3 months, from birth to 7 months, or from birth to 2 years, or as maximum exposure on a single day during those 3 time period". In short, no statistical association between too many vaccines too soon and autism.

There's little more to say about the findings that hasn't already been said. I've talked before about immunisation uptake in siblings of children with autism (see here) and how the general topic of vaccination has been a real source of discussion/debate/argument in some quarters of the autism landscape; more often than not as a result of the disparity between personal experiences vs. the scientific literature.

Appreciating that quite a few people want to draw a line under the whole vaccination-autism affair in light of this and other data quite explicitly detailing no population-wide link between the two, I'm always open to further scientific inquiry on any aspect of autism. Take for example the work by Harumi Jyonouchi and colleagues on SPAD - specific polysaccharide antibody deficiency - in relation to cases of autism (see here) which may or may not be relevant and which is crying out for further independent replication. Or even the suggestion that post-vaccination paracetamol (acetaminophen) use might be tied into risk of autism as per the paper by Schultz and colleagues** (thanks Jen).

And then there are the various reports on cases being conceded on vaccination and 'autism-like symptoms' developing as per Hannah Polling. Indeed, with the n=1 very firmly in place, I note from the linked Time article "she received an unusually large number of vaccines in 2000 (when thimerosal was still in use). Because of a series of ear infections, Hannah had fallen behind in the vaccine schedule, so in a single day she was given five inoculations covering a total of nine diseases: measles, mumps, rubella, polio, varicella, diphtheria, pertussis, tetanus, and Haemophilus influenzae." According to the DeStefano results, the total antigen load was not an issue? So what might have been the issue/s? Did a mitochondrial problem show some involvement or not? (see the CDC FAQs on this topic).

I'm going to finish this post by highlighting just how important vaccination is (see here, again from the CDC), save any charges of irresponsible blogging being levelled against me. At the same time though, realising that no medicine is infallible and that continued vigilance and monitoring is required as per the article by Roberta Kwok*** and the recent flu vaccination - narcolepsy example.

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* DeStefano F. et al. Increasing Exposure to Antibody-Stimulating Proteins and Polysaccharides in Vaccines Is Not Associated with Risk of Autism. J Pediatrics. March 2013.

** Schultz ST. et al. Acetaminophen (paracetamol) use, measles-mumps-rubella vaccination, and autistic disorder: the results of a parent survey. Autism. 2008; 12: 293-307.

*** Kwok R. Vaccines: The real issues in vaccine safety. Nature. 2011; 473: 436-438.

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ResearchBlogging.org
Frank DeStefano, Cristofer S. Price, & Eric S. Weintraub (2013). Increasing Exposure to Antibody-Stimulating Proteins and Polysaccharides in Vaccines Is Not Associated with Risk of Autism The Journal of Pediatrics