Saturday, April 24, 2010

Mercury Models

Not too many weeks ago I declared that I would not weigh in on current event issues unless I felt like it. This declaration was not an indication of my lack of interest in more temporally topical goings-on, but simply an acknowledgement that keeping a blog up-to-date on issues is a pain. I would not be re-examining my declaration at all if I was not changing my mind on addressing a specific issue. That issue is vaccination against infectious diseases.

I should be clear upfront on this: “Most childhood vaccines are so very good that I believe parents who prevent their children from getting them are being negligent.”

Perhaps the above statement is not clear enough for some people. How about this one: “Parents who prevent their children from receiving most childhood vaccines are negligent parents and negligent members of the community as a whole.”

The problem with not vaccinating kids is not simply one of personal risk and responsibility. An unvaccinated kid increases risk to vaccinated children. Vaccines are not 100% effective. In every vaccinated group a significant percentage remain either partially or wholly unprotected. For some vaccines the number of unprotected vaccinated individuals is uncomfortably high. Increasing the number of potential carriers in a population puts vaccinated kids at enhanced risk.

Herd immunity is compromised if the ratio of unvaccinated to vaccinated rises above a certain level.  Vaccination is a communal responsibility, not a personal one.   What could possibly lead people to not vaccinate their kids?

A recent poll shows that as much as 25% of Americans think that vaccines cause autism; as many as 10% of these may refuse to vaccinate their kids. Since this delusional mindset is not evenly spread throughout the US there are pockets where vaccine saturation is not high enough to cause a herd immunity.

Kids in these insufficiently vaccinated communities experience an enhanced level of risk. Kids even visiting these communities are at more risk. Kids in adequately vaccinated communities who are visited by members of the poorly vaccinated communities are put at greater risk. The risk is invisible and potentially deadly.

The issue has been raised by some recent statements I have made where I expressed a lack of support for some vaccinations. Specifically I said that I did not like the VZ (Varicella zoster or chicken pox) vaccine. The statements were not a misquotation and I would say that they were also not taken out of context except that a contextual superstructure has arisen about all vaccine-related statements which inhibit examining vaccinations rationally.

Let me restate my VZ statements: “The VZ vaccine is only partially effective against the minor form of the disease. I have not seen conclusive evidence that it is effective against the acute adult disease. Its widespread use may increase the relative number of non-symptomatic carriers and render non-vaccinated and susceptible populations at risk to an almost undetectable threat. In short it does insufficient good and has potential risks that remain largely unaddressed.”

There should be no mistake that the above statement concerns the effectiveness of a particular vaccine against a particular public health issue. Why then do I find myself answering questions about mercury? I never mentioned mercury. I do not think thimerosal is even used in the VZ vaccine. Even if it was I do not think it would be a significant issue. Mercury in vaccines amounts to around 1 to 2 micrograms per dose. That should not be enough to cause any problems according to all exposure data I have seen, and I have now seen quite a bit.

Mercury is the evil magic loadstone around which a collective fear of vaccines has collected. Mercury can be measured in very small amounts. Mercury is very toxic, even in small amounts. Mercury is a measure of pollution in the environment. Mercury, in general, is bad.

Mercury, in the form of the toxic compound thimerosal, is used in pharmaceuticals because it is toxic. The classic case for using thimerosal arises anecdotally from an outbreak of infections spread from a multi-use vaccination bottle. Several kids got very (life threateningly) ill from an infection caused by a common skin bacterium that contaminated a bottle of a vaccine. Once the bacterium got into the bottle of vaccine it found an environment similar to laboratory culture medium for bacteria. It grew wildly, and the result was a bunch of deathly ill children.

Enter thimerosal. Thimerosal kills bacteria very effectively in very small concentrations. It is stable, so the killing effect lasts. It dilutes to utterly inconsequential levels on injection into the body. Without thimerosal the risks associated with large-scale use of vaccines, especially in places like underdeveloped countries, are significantly increased. This is one of those cases where there is a significant problem and an effective simple solution. We could all use more situations like this in our world.

There are, of course, real issues with using a toxic substance in a pharmaceutical. How much can be used? Is there accumulation? How long does it last in the body? Are there long term effects?

With thimerosal use in vaccines there are some complicating issues with answering some of the questions. Most of these arise from the fact that the dilution rate of thimerosal on injection in the amounts used in vaccines results in a concentration below detectable levels. When something disappears it is kinda like magic.  Magical items can supposedly do magical things.  Without shamans in modern society who can help us answer questions about magic?

Who better to talk about these complex issues than an aging supermodel? Jenny McCarthy is the most identifiable spokesperson for the vaccine-autism link. At one point in time naked pictures of her were downloaded more frequently than Pamela Anderson’s naked pictures. I don’t even know if they can amass statistics like that anymore. She is, apparently, Jim (Ace Ventura pet detective) Carrey’s girlfriend and there may or may not be a sex tape. She has a kid with autism and is the spokesperson for an autism support group which has become a great champion of the mythical vaccine-autism connection.

Much of the information about vaccine safety and deployment requires measured and reasoned investigation. This is not information “developed on the fly” so there is no need for a spokesperson who can “think on their feet”. The perfect spokesperson would be someone who can deliver the same message to multiple audiences, and do so in an attractive and intelligible way. The best spokesperson would also have a backstory that validated their investment in the cause. Jenny McCarthy may actually be an exceedingly good choice for spokesperson. She certainly is a better choice than me. Despite that fact that I would love to go head to head with her in science trivial pursuit; or twister.

I should digress slightly to better explain why I do not think thimerosal is a significant identifiable contributor to risk. I mentioned earlier that each dose of a thimerosal-containing vaccine has 1-2 micrograms of mercury in it. This is not much at all. By contrast, a low mercury compact fluorescent bulb (CFL) has around 5 milligrams of mercury. This is still not much at all, but it is thousands of times more than in a vaccine dose. Some mathematical models predict that breaking a single CFL in a room can generate an atmosphere with around 25 micrograms of mercury per cubic meter of air. Breathing the air in the contaminated room would result in a very small exposure indeed, but it is about as high an exposure as one might get with a lifetime’s worth of immunizations.

The more biochemically savvy of readers should be thinking about the difference between elemental and methyl mercury. Most important environmental exposures are with methyl mercury. An average 8-ounce serving of fish contains around 25 micrograms of mercury. There are so many sources of methylmercury exposure in our modern environment that it is impossible to identify them all. Most beat vaccine exposure levels by at least an order of magnitude.

This means that if we were to remove all vaccine mercury the exposure rate would only be decreased by a very small fraction of a percent. Mercury is very toxic so reducing exposure levels, even by a small amount, is a good thing. If mercury causes autism then refusing vaccines will not reduce the rate of autism by any measurable amount. There are considerable and rational reasons to question if mercury can cause autism, but I am not addressing them in this already-too-long post. The point here is that: even if mercury is causal to autism the vaccines have no measurable effect on the probability of developing autism.

My original question was: “Why am I being confronted with mercury questions?”

The mercury questions have been answered repeatedly. Unfortunately they have too good a spokesperson to be simply answered and forgotten. The mercury questions get louder and more disruptive the more times they are answered. They bleed over into all discussions of vaccines. When I raise concerns over the public health efficacy and risk associated with a single vaccine it is filed as either a “for” or an “against” argument for the confrontation that is rooted in the mercury question. Important questions are drowned out and the answers to the base questions are ignored.

The mercury issues have such cultural momentum that should Ms. McCarthy change her tune the myth would persist long enough to put many more children’s lives at risk.

One of the fastest growing causes of death, in cases of treatable cancer, is refusal of treatment. Somehow patients get convinced that something will work better, or that they will be magically cured. There is little reason can do to convince the individual of the incorrectness of choosing a magical cure. Many people will become more firmly convinced of the rightness of their belief when confronted by evidence that it is wrong. The more evidence they are confronted with the more firmly they believe.

When believers raise their voices they can create converts. Converts are not those who have become convinced by evidence, or those who have weighed reasoned positions and arrived at their own; these are people who came to believe. There are few easy ways to change a belief. The best one can reasonably hope for is a modification of the behavior motivated by the belief. As a mostly secular society we are best at approaching the impact of irrational beliefs by modulating the behavior they motivate, rather than addressing the belief itself. This is one significant reason why so many people, who believe that autism is caused by vaccines, get their children vaccinated anyway.

Can we go deeper and address beliefs in order to create a more stable and reasoned public heath condition?

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