Tuesday, February 3, 2009

Thought experiment.

This summer I was musing about vaccination and came up with an interesting thought experiment that I think is worthy of repetition:

What if we could separate the public and private benefits of vaccination? Imagine there was a 'vaccine' for a serious illness, and it's hard not to think of AIDS, BUT it only conferred herd immunity not individual immunity. That is, there would be no individual benefit to taking it, but, if sufficient people were vaccinated, the disease would have a growth rate less than one and be eliminated.

How would such a thing be possible you ask? Simple, the vaccine would prevent you from transmitting the disease but would not prevent you from getting it. Assuming the vaccine had some level of side effects - say 1 in a million actually get AIDS from the vaccine - what do you think the rate of uptake would be?

Sad to say, I'm guessing it would be very low. In fact I'm guessing that even with NO side effects the rate of uptake would be low. I'm not sure what the R0 for HIV is, but let's imagine that there needs to be 75% coverage to establish herd immunity. IF such a vaccine were possible should the government introduce legislation to make vaccination mandatory? Or would it be sufficient just to offer an incentive? How much? $10, $100, $1000? Should individuals who contract AIDS from the vaccine be compensated or did they accept this risk when they agreed to be compensated? Do you think we could realistically ever achieve a 75% vaccination rate?

And then just to make this more complicated, imagine this was a decision you were making not for yourself but for your children.....

Food for thought....

Before we move on, here are some other, older postings concerning vaccines and vaccination that you might find interesting.

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