Study casts new doubts on HPV vaccine
The highly touted treatment to prevent cervical cancer may be less effective than previously thought, findings suggest.
By Thomas H. Maugh II and Jia-Rui Chong
Times Staff Writers
May 10, 2007

New data on the controversial HPV vaccine designed to prevent cervical cancer have raised serious questions about its efficacy, researchers reported today, potentially undercutting the efforts in many states to make vaccination mandatory.Although the vaccine, called Gardasil, blocked about 100% of infections by the two human papilloma virus strains it targets, it reduced the incidence of cancer precursors by only 17% overall.

Part of the reason was that many of the teenage girls and young women in the three-year study had already been exposed to the virus, according to the report in the New England Journal of Medicine.
But the data also hinted that blocking the targeted strains might have opened an ecological niche that allowed the flourishing of HPV strains previously considered to be minor players, partially offsetting the vaccine's protection. the rest