Vaccination is to Autism as Tobacco is to Lung Cancer... Ummm, What?!

Continuing this thread on vaccination against childhood diseases, a friend of mine pointed out the article Vaccine Court: Autism Debate Continues from the Huffington Post, authored by Robert F. Kennedy Jr. and David Kirby. You might take a few minutes and give it a good read.

There are two big issues at play in this article - particularly within the context of vaccination legislation - that should really be presented more distinctly. These are (1) the extent to which vaccines contribute to the incidence of autism or autism spectrum disorders (ASD), and (2) the consequences of whether or not we vaccinate our population against these types of infections. What I realized in reading this article is that talking ad nauseum about the first issue without also addressing the second is, quite frankly irresponsible and dangerous.

Before I explain why, lets mention some important background information. First, I will distinguish here between the infection (i.e. simply hosting a viruses, say HIV) and the disease (i.e. the symptoms caused by that virus, which for HIV would be AIDS). This is important because not all infections lead to disease (i.e. injury or death).

We also need to understand the role of herd immunity as it relates to infections that transmit from person to person. In short, a certain percent of the population needs to be vaccinated (or otherwise resistant) to infection in order to prevent a few infections from becoming a big epidemic. If to few are vaccinated, epidemics can take off and spread through the unvaccinated portion of the population, which is bad.

Think of vaccinated and unvaccinated individuals and fire-proof and flammable wooden sticks, respectively. A population then would be analogous to a pile of such sticks. With enough fire-proof (vaccinated) sticks in the pile, a single match won't start much of a fire. On the other hand, too few fire-proof sticks (too few vaccinated individuals), and whoosh! The pile goes up in flames. In the case of infectious diseases, the proportion vaccinated needs to be relatively high in order to prevent outbreaks, usually upwards of 80-90% in a given community.

Back to our two main questions. Speaking as someone with a strong quantitative background (i.e. an applied mathematics graduate student) the first thing I want to know regarding issue (1) is what evidence exists that children receiving vaccines show a significantly higher rate of ASD relative to unvaccinated children (all else being equal), and how much higher is it?

This next bit is what they leave out of the article, and is of fundamental importance to the vaccine-autism/ASD controversy: how we evaluate the answers we receive to the first question depends enormously on what we learn from issue (2). In short, if we have to pick our poison we had better know which option is worse! If we compare a sufficiently vaccinated population and one with low or no vaccination (all else being equal), how do they compare on both childhood disease and autism?

The evidence I have seen and that the experts have summarized for the rest of us suggests that there is at worst a relatively small number of cases where vaccines caused significant harm to the people that they were intended to protect. This is true of most drugs, medical treatments, safety mechanisms in automobiles, and countless other things we make and provide one another - simply put, nothing is perfect though we can usually do a little bit better and a whole lot worse.

So lets revisit the common (and very flawed) argument against vaccines that goes something like this: "vaccines cause injury and death, therefore they are bad and we should stop pushing them on the public." Sounds reasonable, right? Well, it isn't. A more relevant statement to make would go something like "if vaccines cause injury and death, we should categorize them as bad if they caused more injury and death than the diseases which they prevent."

While this comparison seems like a no-brainer, it hardly ever gets as much thought as it deserves! This is in part because of the concern (and in many cases fear) many parents have over the perceived risk of vaccines, and also because there is more anecdotal evidence on the vaccine-ASD issue floating around out there than on the vaccinated-unvaccinated issue despite the often unnoticed historical figures. We also have more control over our own individual choices about vaccination compared to our contracting diphtheria, for example, which focuses attention there instead of on the larger issue of society doing the greatest for its people.

This my friends, is why so many public health professionals and concerned citizens push so strongly to fight all the anti-vaccination rhetoric and fear that pervades that ether of public information and knowledge. Vaccines may cause great harm to a very small few - each and every case meaning the world to someone, and each deserving the appropriate level of recognition and in some cases redress.

But without vaccines, and without enough vaccine coverage to ensure we stand above the herd immunity threshold, the cost in human lives and human suffering would be much greater. And that folks, just isn't an acceptable alternative.

I'll leave you to look back to the tobacco analogy drawn in the article above, and how irresponsible it is to compare the tobacco industry with the medical industry. Tobacco products don't do much good for society (as far as I know) - and they certainly don't protect little boys and girls from the wrath of so many truly horrible diseases that once plagued our population.