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December 09, 2008

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Woo hoo!

Ahem.

What I mean to say is:

Hey, spiffy, that's great news! Go humanity!

Yay!

This is amazing. So good to see this work is still being done, and that it's so close to being put into use.

Awesome news.

It's worth pointing out that the effectiveness rate of a vaccine actually understates its impact. After all, diseases like malaria rely upon a host population to spread. Reduce that host population, and you can reduce the rate of infection - not just in those who have been vaccinated and in whom the vaccination has proven preventative, but for the population at large.

Take, for example, another recently-introduced early childhood vaccine. The pneumococcal conjugate vaccine was targeted at children under the age of two. After two years of widespread administration, rates of infection of the targeted strains dropped by 78% among children under two. But here's the really good news: "Among children younger than five years, there was a 59 percent decline in rates of invasive disease. Even adult populations showed reduced rates of invasive disease, with 32 percent fewer cases in persons 20 to 39 years, 8 percent less disease in those 40 to 64 years, and an 18 percent reduction in invasive infection among persons 65 years or older."

There are two take-away points from that case study. The first is that vaccines like this can act very rapidly - the authors concluded that it was having a dramatic effect within the first year. The second is that an early-childhood vaccine can have a dramatic impact on the population at large, as well. So much the better.

That is excellent news. Thanks for giving me the heads up on this.

After all, diseases like malaria rely upon a host population to spread. Reduce that host population, and you can reduce the rate of infection - not just in those who have been vaccinated and in whom the vaccination has proven preventative, but for the population at large.

It's actually even better than this. There's a fairly strong relationship between how widespread a disease-causing organism is and how nasty it can afford to be to its host. Cutting the number of malaria infections in half will, according to virulence theory, create a strong selection pressure for "weaker" malarial infections in those that acquire it despite vaccination.

Widespread vaccination attacks disease on three fronts: fewer people are infected, there are fewer reserves of disease, and the pathogen is "encouraged" to be nicer to those it does infect. This is incredibly good news.

This is great news, but it is worth pausing to note that world does not need to wait for the development of an effective vaccine to substantially reduce morbidity and mortality from malaria in Africa. Heck, the basic provision of mosquito nets has been proven time and again to be an evidence-based intervention.

What this does suggest is not that we should not spend money on developing vaccines, but that due attention to the social determinants of health on a global scale ought to be a top priority. For much more on this, of course, see the work of, among many others, Amartya Sen and Paul Farmer.

Robert M.,

Thanks for bringing up the virulence point. It's (good) news to me.

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