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Originally Posted by godfry n. glad
Quote:
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Ironically, in an analysis of a localized measles outbreak in France, nearly 74% of those infected by the virus were not vaccinated. And of those infected, 29% of the parents were anti-vaccine.
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Huh?
So, 26% of those infected by the virus were vaccinated? That's a hellish high vaccine failure rate. |
Those 26% are not the vaccine failure rate. Again, if you
(A) take the whole set of people who are vaccinated and look at the percentage of these who get sick afterwards, or
(B) take the set of people who get sick and look at the percentage of these who have been vaccinated before,
those are conceptually
two completely different numbers.
Quote:
Originally Posted by But
Quote:
Originally Posted by godfry n. glad
So in any random exposed population, how many vaccinated individuals would you expect to develop the infection?
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Obviously, that depends on the percentage of vaccinated people in that population. Let's say 91% are vaccinated, the vaccine has a failure rate of 5% and 90% of unvaccinated people get the disease.
Then
P(sick | vaccinated) = 5%.
P(vaccinated | sick) = P(vaccinated and sick) / P(sick) = 0.91 * 0.05 / (0.91 * 0.05 + 0.09 * 0.9) = (approx.) 0.36 = 36%
If you assume that everyone is vaccinated and the vaccine has a non-zero failure rate, you would get that 100% of those infected were vaccinated. |