Vaccines prevent, but can't treat HPV - study

CHICAGO, Aug 15 (Reuters) Vaccines designed to prevent infection from two strains of the human papillomavirus virus that cause most cases of cervical cancer offer no benefit as a treatment for women who are already infected, U S researchers said.

''You should not get the vaccine because you want to treat an existing infection,'' said Allen Hildesheim of the National Cancer Institute yesterday whose study appears in the Journal of the American Medical Association.

Hildesheim said the arrival of HPV vaccines -- Merck&Co.'s Gardasil and another in development by GlaxoSmithKline called Cervarix, has raised awareness about the link between the sexually transmitted human papillomavirus and cervical cancer. But it has also raised questions.

''We felt it was important to address the question head on,'' Hildesheim said in a telephone interview.

He and colleagues studied Cervarix in two provinces of Costa Rica that included 2,189 women aged 18 to 25 who were positive for HPV infection. They found the vaccine showed no sign of clearing the infection any faster than a placebo.

''These results are completely expected,'' said Liad Diamond, a Glaxo spokeswoman.

Both Merck and Glaxo said their vaccines are not intended to treat HPV infections, and the study's findings confirm their own research.

Gardasil and Cervarix protect against HPV strains 16 and 18 that cause about 70 percent of cervical cancers. Gardasil also protects against HPV strains 6 and 11. It is approved in the United States for young women aged 9 to 26.

The U S Centers for Disease Control and Prevention recommends Gardasil for routine use in girls aged 11 to 12.

Hildesheim said the study underscores the need for early vaccination. But he said a number of questions remain, including whether the vaccine might protect previously infected women from future infections, and whether that would help reduce the risk of cervical cancer.

Merck medical director Dr. Richard Haupt said the study underscores the importance of vaccinating women before they are sexually active. The company is studying to what extent the vaccine can protect older women as well.

''There is still more information that needs to be known,'' he said.

Cervical cancer is the second most common type of tumors in women and the leading cause of cancer deaths in some countries.

Infection is common, with more than a quarter of U S girls and women aged 14 to 59 infected. About 90 percent of infections clear within two years.

REUTERS AE HT0935