In the most recent London Review of Books, Hugh Pennington has a generally excellent article on measles and erroneous (to put it charitably) research linking the combined MMR vaccine to autism. It’s a pity therefore that, on a peripheral issue, he perpetuates an equally glaring error, saying
As I’ve pointed out previously Hardin’s story was, in historical terms, a load of tripe.‘Most people have an intuitive appreciation that the best vaccine programme, from an individual’s point of view, is one where almost everyone else is vaccinated while they are not, so that they are indirectly protected without incurring any of the risks or inconvenience associated with direct protection.’ If too many people act in this way, the infection becomes commoner in the population as a whole, and returns as a real and significant threat to the unimmunised. This is a modern version of the ‘Tragedy of the Commons’ described by Garrett Hardin in his influential 1968 essay: 16th-century English peasants had free grazing on commons; their need to supplement food supplies and income was very great; the resulting overgrazing wrecked the commons for everyone.
It’s interesting to note that, in repeating Hardin’s story, Pennington adds the spurious specificity of “16th century England”, whereas Hardin’s account was not specific regarding dates and places, and therefore harder to refute. This is characteristic of the way in which factoids are propagated.
{ 6 comments }
Anthony 07.20.04 at 12:44 pm
While your demolition of Hardin’s story may be valid, the tragedy of the commons is useful in explaining the situation when some people do not to vaccinate yet benefit from others socially responsible decision to vaccinate. Herd immunity is a shared resource, and the only people who can with any validity remove part of that resource are those who have real contra-indications to vaccines.
Individual-centred models of bio-ethical reasoning are currently vary much in fashion – and I would largely agree with this on most health issues – but on the issue of vaccination there is such a thing as society and the tragedy of the herd is a likely consequence of low vaccination rates.
Thanks for the heads up on the Hugh Pennington article.
eudoxis 07.20.04 at 7:07 pm
Pennington makes an error in the measles story as well. The original Wakefield et al. paper was a case report. Case reports don’t pretend to be scientific studies, they are published observations of clinical presentations. The British press established the causal link.
Anthony 07.20.04 at 7:18 pm
To be pedantic, it was a case series investigating 12 children that was investigated and studied, rather than a single case report. It has been referred to as a study even by its detractors. However, you are correct in that the “study” was little more than a collection of case reports and certainly not deserving of the attention it received, or the conclusions draw from it by some.
You are also wrong about the British Press, as the press conference Andrew Wakefield made the link by suggesting parents should opt for single jabs against mumps, measles and rubella instead of MMR vaccine.
The press picked up the ball and ran.
eudoxis 07.20.04 at 8:12 pm
Anthony,
A probabilistic benefit of the herd extends only to those who are not vaccinated. Individuals who choose not to vaccinate increase the chance that they and others who are not immunized will contract the disease. The tipping point at which the environmental load is reduced enough to allow any protection for defectors is quit a bit higher than 50% immunized. At low levels of immunization, there is no herd effect. At high levels of immunization, the relative cost to the defector and others not immunized increases. In each case, the danger that the defector poses to himself is far greater than the benefit provided by the herd. So, the argument not to vaccinate fails on both individual and herd counts.
dsquared 07.22.04 at 3:04 am
Tangentially to which, can someone explain to me when and why measles was upgraded from “minor childhod ailment” to “scourge upon our land”?
I distinctly remember that when there was a “measles epidemic” in the 1970s in the UK, I was sent round to the houses of the kids who had got it, so that I could “get it over with”. I don’t think I was brought up by gypsies or Christian Scientists, but was this absolutely abnormal?
John Quiggin 07.22.04 at 6:21 am
DD, the Pennington article is quite good on this. Highly infectious diseases like measles look harmless because the great majority of those infected survive with no lasting ill-effects. But the mortality and morbidity can still be quite severe, because nearly everyone gets the diseases.
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