Adverse Effects of Vaccines: Evidence and Causality

26 Aug

The United States Institute of Medicine (IOM) has just published a lengthy report, Adverse Effects of Vaccines: Evidence and Causality.

The short summary, via Reuters, is: “the big take-home message is that we found only a few cases in which vaccines can cause adverse side effects, and the vast majority of those are short-term and self-limiting.”

As to autism? There are two main theories of autism and vaccines: MMR and Thimerosal. The autism and MMR theory is one of the most studied and most clear. The committee found that the research “Favors Rejection”. As in,

The committee concluded the evidence favors rejection of five vaccine-adverse event relationships. These include MMR vaccine and type 1 diabetes, DTaP vaccine and type 1 diabetes, MMR vaccine and autism, inactivated influenza vaccine and asthma exacerbation or reactive airway disease episodes, and inactivated influenza vaccine and Bell’s palsy. The evidence base for these conclusions consisted of epidemiologic studies reporting no increased risk; this evidence was not countered by mechanistic evidence

The epidemiological evidence says there is no increased risk. There is no good mechanism known or postulated whereby MMR could cause autism.

Thimerosal is barely mentioned in the report, with only 7 mentions. As far as autism+thimerosal is concerned, the IOM reviewed the literature years back and found no evidence of a link. Since that time, the evidence has grown greater against a link and thimerosal has been removed from the routine pediatric vaccine schedule (e.g. Price et al. Prenatal and Infant Exposure to Thimerosal From Vaccines and Immunoglobulins and Risk of Autism
and, while not specific to autism, Thomson et al. Early Thimerosal Exposure and Neuropsychological Outcomes at 7 to 10 Years)

Previous IOM reports on Thimerosal: Immunization safety review: Thimerosal -containing vaccines and neurodevelopmental disorders.

Previous IOM report on vaccines and autism (especially MMR and thimerosal): Immunization safety review: Vaccines and autism.

I expect much criticism to be focused on the IOM from some circles. The arguments will likely focus on “look at all the vaccines which have not been specifically studied in relation to autism”. It is a semi valid point. The problems with the argument are many, but include: what mechanism is there for these vaccines to cause autism? (Too many too soon is a slogan, not a scientific argument). Without a mechanism, and without some sort of data showing a possible link, there is such a low possibility of finding anything that resources are best spent elsewhere. In addition, the studies to date give a reasonable proxy for vaccine exposure: the more thimerosal an infant was exposed to, the more vaccines. Thimerosal exposure becomes a proxy for the number of vaccines. It has been shown (multiple times) that there isn’t an increased risk for autism with thimerosal.

Lastly, if you read the criticisms claiming “but they’ve only studied one vaccine and one ingredient”, watch for the intellectual honesty. That’s the part where the critic admits that “they’ve only studied one vaccine and one ingredient, and they found that those don’t increase the risk of autism“. Most critics in this field are cake-eaters. They want their cake (the argument that the studies have only looked in depth at MMR and thimerosal) and they want to eat it too (by denying the results of those studies). It’s predictable.

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2 Responses to “Adverse Effects of Vaccines: Evidence and Causality”

  1. Randhil November 24, 2011 at 06:20 #

    That’s the best awsner of all time! JMHO

Trackbacks/Pingbacks

  1. South Park Mocks Aspergers and Vaccine Fears. « Alternative Health Answers - October 7, 2011

    […] Adverse Effects of Vaccines: Evidence and Causality (leftbrainrightbrain.co.uk) […]

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