--- Sonja wrote: <huge snip> > Does population wide vacination make viruses that > have been around for ages more virulent?
Off the top of my head, no, I am not aware of that being a significant problem, although theoretically it _could_ select for a hardier type. Some viruses, like influenza A, are so intrinsically variable that vaccines could only select a type out for a year or two (which is one of the reasons I gather that making a vaccine for HIV is so difficult - it has inherent mutability in the components (such as outer coating) that one uses). I think that _vaccination_ pressure is different from _antimicrobial_ (or virucidal) pressure when it comes to selecting out hardier or more virulent bugs, because the former is _indirectly_ improving target host defenses, while the latter is acting _directly on_ the pathogen in question. But I'm going to have to look into that to be certain... Ben? What do you think? Debbi __________________________________________________ Do you Yahoo!? New DSL Internet Access from SBC & Yahoo! http://sbc.yahoo.com _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
