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.
For The Record
Los Angeles Times Friday May 11, 2007 Home Edition Main News Part A Page 2 National Desk 1 inches; 37 words Type of Material: Correction
HPV vaccine: An article in Thursday's Section A about studies on human papillomavirus said that one by Johns Hopkins University researchers looked at 100 women with newly diagnosed throat cancers. The 100 patients were men and women.
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.
In an editorial in the same issue of the journal, Dr. George F. Sawaya and Dr. Karen Smith-McCune of UC San Francisco called the benefits of the highly touted vaccine "modest," and said that young women and their parents should take "a cautious approach" to vaccination because of the many unanswered questions about its efficacy.
"The effect is fairly small," Sawaya said in a telephone interview. "The recommendation for widespread vaccination of women after they become sexually active may need to be rethought."
The maker of the vaccine, Merck & Co., said the studies clearly showed that the vaccine prevented infections from the two HPV strains and reduced the number of precancerous lesions caused by the them.
Initial optimism
Gardasil was approved by the Food and Drug Administration in June amid cheers that it could largely prevent cervical cancer among vaccinated women.
The Centers for Disease Control and Prevention quickly recommended that all girls and women ages 11 to 26 receive the vaccine.
The American Cancer Society seconded the recommendation, although it concluded that there was "insufficient evidence" of benefit among women ages 19 to 26 because so many had already been exposed to the virus.
At least 24 state legislatures have introduced bills calling for mandatory vaccination of girls in their early teens or younger.
A bill was introduced in California, but its prospects are uncertain because of complaints from parents that vaccination may encourage sexual promiscuity.
