Posted by Tara Smith on May 1, 2007 12:34 PM

A few weeks back during the whole Egnor kerfuffle, I mentioned how important an understanding of evolutionary biology was to many areas of epidemiology, and specifically, for vaccine development and implementation. As one example, I brought up the phenomenon of serotype replacement, which can occur due to the use of what are called “multi-valent vaccines.” Essentially, these vaccines include strains of pathogens which are either the most common, or the most likely to cause disease–thereby protecting individuals from infection with these specific serotypes, but not making the recipient immune to infection with other strains that aren’t included in the vaccine formulation. The concern is, then, that once those types are reduced in the population via vaccination, other serotypes can come along and fill the niche that they’ve vacated. A recent story by Helen Branswell notes that this is exactly what’s happening with pneumococci:

(Continued at Aetiology)