Doubts arise about cancer vaccine

Benefits of HPV shots called `modest'

young women, parents are urged to be cautious

May 10, 2007|By Thomas H. Maugh II and Jia-Rui Chong | Thomas H. Maugh II and Jia-Rui Chong,LOS ANGELES TIMES

New data on the HPV vaccine designed to prevent cervical cancer have raised serious questions about its efficacy, researchers reported today, perhaps undercutting the efforts in many states to make vaccination mandatory.

Although the Merck vaccine, called Gardasil, blocked nearly 100 percent of infections by the two HPV strains it targets, it reduced the incidence of cancer precursors by only 17 percent overall.

Part of the reason was that many of the teenage girls and young women who participated in the three-year study had been exposed to the virus, according to the report in the New England Journal of Medicine.

The data also hinted that blocking the targeted strains might have allowed the flourishing of HPV strains previously considered to be minor factors, partly offsetting the vaccine's protection.

In an editorial in the same issue of the journal, Dr. George F. Sawaya and Dr. Karen Smith-Carter of the University of California, San Francisco called the benefits of the vaccine "modest" and said 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 prevents infections from the two HPV strains and reduces the number of pre-cancerous lesions caused by them.

Immunologist W. Martin Kast of the Keck School of Medicine at the University of Southern California, who was not involved in the research, said the study did not go on long enough to prove the vaccine's worth.

"In a three-year follow-up, it is very hard to reach statistical significance in a disease process that takes about a decade to fully develop," he said. "Thus it is not fair to state that the vaccine is not effective. It will be, but it needs more time to materialize."

Gardasil was approved by the Food and Drug Administration in June amid hopes that it might largely prevent cervical cancer among women who were vaccinated.

The Centers for Disease Control quickly recommended that all women ages 11 to 26 receive the vaccine.

The American Cancer Society seconded that recommendation but concluded that there was "insufficient evidence" of benefit among women ages 19 to 26 because so many had been exposed to the virus.

At least 24 state legislatures have introduced bills calling for the mandatory vaccination of girls in their early teens or younger.

The debate over mandatory use of the vaccine has been further complicated by the cost of the treatment, about $360 for the vaccine plus the cost of three office visits.

Thomas H. Maugh II and Jia-Rui Chong write for the Los Angeles Times.

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