Nov 04 2010

Germ Theory Denial

At the more extreme end of the anti-vaccine culture is the denial that vaccines work at all, and even further beyond that is germ theory denial. Although I don’t have any statistics, it is my impression that most anti-vaxers do not go that far, but a fair number of them do. Most notably is Bill Maher, who flirts with the germ theory denial and denial of vaccine efficacy. Of course, if germs don’t cause disease, then vaccine are useless. Even if they do, an anti-vaxer might be tempted to claim that vaccines do not work, despite the overwhelming evidence that they do.

That an educated person in a 21st century industrialized nation could deny such a basic fact of science deserves an explanation. I think it is enough to say that it is a triumph of ideology over reason. We see this also in evolution denial, HIV denial, even holocaust denial. But more than ideology, It seems to also flow from an intolerance to complexity and ambiguity. We like to have our ideology pure, unsullied by moral or factual complexity. Humans generally abhor gray zones.

So if one thinks that vaccines are risky and can cause serious side effects it may be easier to also believe that they do not work, rather than have to wrestle with the notion that there are risks and benefits that need to be balanced. Not everyone goes down this rabbit hole, but many do.

I was recently sent a link to this conversation in the comments to an AVN blog post – the AVN stands for Australian Vaccine Network, but critics argue it should stand for the Anti-Vaccine Network as that is their agenda. They have been on hard times recently, as their charity status was recently revoked. While this is the comment of an anonymous internet crank, it is fairly representative of germ theory denial. It represents the tactics of denialism in general, and therefore serves as a suitable example.

One strategy of denial is to point to apparent inconsistencies or anomalies in the accepted science and then claim that this calls into question the most fundamental facts of that science. For example creationists are fond of pointing out apparent anomalies in the sequence of evolution (which are easily explained by the incompleteness of the fossil record) and then argue that therefore life did not evolve. In the case of germ theory denial we are dealing with the complexities of the immune system. Commenter Punter writes:

If one immune cell can match many different antigens then why do we need a different flu vaccine for every minor variant of the flu strain?

He is arguing that current theories of immune function are inconsistent because there would need to be an infinite number of T-cells in order to respond to any potential infection. If  the answer is that T-cells can respond to different antigens, then why isn’t one flu vaccine (or infection) sufficient to cover all flu strains? In short, Punter needs to pick up an immunology textbook. I don’t know where  he is getting his information from. It seems as if most of it is just made up ad hoc, and perhaps the rest comes from germ denial websites. But there are answers to all his questions in textbooks of immunology.

The unstated major premise of Punter’s questions above is that immunoreactivity is an all-or-nothing response – that a T-cell either reacts to an antigen or it doesn’t. This is not true, there is a continuum of intensity of reactivity. Antigens (things that react with the immune system) bind to receptors on immune cells. The binding is based upon shape and chemical properties. But the fit does not have to be perfect – any amount of a fit will result in activation of the immune cell. The better the fit, the greater the response, because then more antigens will spend more time in intimate contact with the cell receptors. It’s a graded response.

One of the responses to such antigen stimulation is for the immune cells to reproduce, and when they do they create variations of the original cell – the receptors are similar to but slightly different than the receptors on the original immune cell that reacted to the antigen. Among these cells there will be some that react even better to the antigen, and these will have an even greater response than the original immune cell. They further reproduce with more variation followed by further selection. In essence, the immune cells rapidly evolve greater and greater affinity for the antigen, until you have a population of immune cells with a robust reaction to the antigen. These proliferate and mount a vigorous immune response, and create memory B-cells which will hang around for years and remember the specific antigen.

Punter is thinking in too simplistic terms – but a basic description of immune function solves all the confusion. Essentially our immune systems produce millions of variations of immune cells with a variety of affinities, in order to react to any possible antigen. Once an antigen is encountered, it then goes through an evolutionary process of variation and selection to fine tune the affinity for the specific antigen. This explains why it takes time to mount an immune response against a novel pathogen, and also how immunity works – the next time around there will already be cells that are fine-tuned to the specific pathogen.

But then why do we need a new flu vaccine every year, and why do infectious diseases differ in this regard – some you only get once, while others you can get an unlimited number of times? Well, pathogens evolve too. Many viruses have stable regions that confer their critical activity – allow them to enter cells and do what they do. But they are hidden behind highly variable regions – regions that vary greatly and evolve rapidly. The variable regions allow viruses to evade the immune system, and they define each new strain of flu virus, for example. New flu strains keep one step ahead of immunity, allowing them to continue to spread. This also explains why older individuals, who have seen many flu seasons and perhaps received many flu vaccines, sometimes have partial immunity to flu strains as they come back around. They may be similar to (but not identical to) strains against which they have immunity – and so they have partial immunity. Again, we see that immune affinity is not all-or-nothing. Essentially, they are already partially fine-tuned to the new strains and can mount a quicker response.

Punter simply does not understand basic immunology, any more than your average creationist understands basic population genetics. But internet warriors can content themselves by arguing with non-scientists, and then feeling vindicated when they cannot adequately answer complex scientific questions. Try asking an immunologist.

In another comment Punter offers this gem of denialism:

This is the part you don’t understand, nay, won’t understand. Every one of your “explanations” is not an explanation but an excuse. Like when those who believed in the geocentric universe came up with “concentric circles” to describe the planetary movements. Believe me there was plenty of detail, but it was all made up. Every bit of it. Just like virology/immunology. Every single thing they say is merely a hypothesis. Immune system memory or germ pathogenicity have never been observed they are simply inferred from two and only two observed phenomena.

The two observations that the germ theory/vaccination paradigm are based on are a) diseases sometimes happen in clusters (although often don’t); and b) for some diseases people only seem to get them a few times (perhaps only once) in their lifetime (pox and measles are obviously the diseases most commonly thought of with those properties).

It is important to recognize up front that Punter is just making this up, and it is completely incorrect. For such broad claims no one or few references suffice. Rather, textbooks filled with hundreds of references are required to cover this territory. Infectious disease and immunology are fairly advanced sciences, with each component built upon and supporting more basic components. To say that it is all based on these two observations is willfully ignorant.

To summarize just a few of the other observations over the last century or so: Some disease don’t just cluster, they spread through contact. Some require physical contact, some the ingestion of food or water, and other spread through water droplets. Infectious disease specialists can track the spread of an infectious disease and see how it spread, and then even locate the source.

Further, steps can be taken to reduce the spread of an infectious disease by addressing the mechanism of infection. Hand washing reduces the spread of infections in hospitals (remember Semelweiss?). Cooking food reduces the spread of food-borne infections. Spraying for insects reduces the spread of diseases spread by insect bites (malaria was wiped out in the US by the CDC’s program and reducing mosquitoes). Wearing face masks reduces the spread of droplet-spread infections. The infection paradigm has been tested in this manner thousands of times, and has proven remarkably useful and predictive. But Punter and his ilk seem content to pontificate within their fortress of profound ignorance.

The second component – that some disease often do not repeat, is certainly a basic observation of immunity, but we are at least a century beyond such fundamental observations. We have fleshed out (not simply by making up hypotheses but by thousands of experiments) many of the details of immune system function and its underlying genetics. We can see these cells in action, and are learning how to manipulate the immune system to prevent tissue rejection or reduce auto-immune diseases. We are certainly nowhere near a complete understanding of the immune system – it is very complex, but no knowing everything is not the equivalent of knowing nothing. Again – I invite Punter to pick up a basic textbook of immunology.

Conclusion

Denialism is always fascinating – the bald-faced denial of facts that are fully in evidence and easily verifiable. It is a testament to the profound psychological effect that ideology can have on the human brain, and the mechanisms by which it is maintained. And before we wax too self-righteous as skeptics in this regard, we must always remember that we are all susceptible to these psychological mechanisms. We are all human. That is precisely why we need the rigorous, transparent, and self-critical process of science to sort through complex questions such as disease and immunity.

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