Last login: Wednesday, September 8, 2010
Very interesting numbers. The CDC statement was accurate, but not very informative. I think for normal people to understand what the CDC was trying to say you have to put some numbers to it:
Let's say you have a town (or, middle school) of 1000 people, and assume all of them (100%) are exposed to pertussis. And, let's assume that 90% of the people are vaccinated. Now, the vaccine is 85% protective. So this results in:
* 100 infections among the unvaccinated group (100 x 100%)
* 135 infections among the vaccinated group (900 x 15%)
That's more cases among vaccinated people than unvaccinated, but it's because almost everyone is vaccinated and the vaccine protects about 4 out of 5 of those people. And that's almost exactly what is reported for San Diego. (Particularly if you assume poor protection in the under 6 month old infants who have only been partially vaccinated (29 cases). The first dose only gives 15-20% protection)
* The pertussis vaccine is 85% effective. This is according to the clinical study cited on the pertussis vaccine package, and it is also the average efficacy found in a number of different clinical trial studies published.
September 8, 2010 at 9:38 a.m.
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