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Old 12th March 2008, 07:42 AM   #116
Deetee
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Join Date: Jul 2003
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Originally Posted by Beth View Post
Someone - can't recall who - has recently posted about the problems of different varieties of an illness (was it hepatitus?) emerging such that the total number of cases doesn't reallly change, only the strains of the disease. That was quite interesting. Not something I'd thought about before, but makes sense.
Apologies of I've missed anything - but I've had a week away and not up with every post on the threads.

Beth, you are referring I think to the issue of serotype replacement. This happens when strains of the infection that are not covered by the vaccine try and fill the niche left behind as infection rates drop. However, with all the vaccines I know about, the replacement is still a tiny fraction of the previous total. So no, the total numbers of cases are not the same, they are still significantly less. The main vaccine this occurs with is pneumococcal, but it also affects others.

Antivaxers will point to serotype replacement, trying to disguise the actual numbers so that someone with an eagle eye cannot imediately rumble them.

Here is a prime example, quoting word for word the paragraph from the "insideVaccines" blog:
Quote:
The incidence of Hib meningitis decreased 69% during the 1-year period after initiation of Hib immunization (from 2.62 to 0.81 cases/100,000 person-years; P<.001). In contrast, the incidence for H. influenzae type a meningitis increased 8-fold.

Therefore, Hib immunization contributed to an increased risk for H. influenzae type a meningitis through selection of circulating H. influenzae type a clones.
Anyone reading this would be rather scared that by preventing Hib B, all one was doing was replacing it with even more type A than there was type B to begin with.

Not so.

The actual source of the "cherry picked" quote says this:
Quote:
The incidence of Hib meningitis decreased 69% during the 1-year period after initiation of Hib immunization (from 2.62 to 0.81 cases/100,000 person-years; P<.001). In contrast, the incidence for H. influenzae type a meningitis increased 8-fold (from 0.02 to 0.16 cases/100,000 person-years; P=.008).
Therefore, Hib immunization contributed to an increased risk for H. influenzae type a meningitis through selection of circulating H. influenzae type a clones. The risk attributable to serotype replacement is small in comparison to the large reduction in Hib meningitis due to immunization.
As you can see, in red I have added the sections that were deliberately removed from the quote on "InsideVaccines".
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