Cervical cancer vaccine has risks

WASHINGTON – A vaccine that blocks infection by the four virus types that cause most cervical cancers and genital warts appears safe and effective, but may actually increase the chance of disease in some patients, according to Food and Drug Administration documents released Wednesday.

Merck &Co. seeks FDA approval for its Gardasil vaccine against four types of human papilloma virus, or HPV. Two of those four types are believed responsible for about 70 percent of cervical cancer cases. The cancer kills roughly 3,500 U.S. women a year; the other two types cause 90 percent of genital wart cases.

An FDA panel of outside experts is to meet today to discuss approving the vaccine.

Merck said the vaccine has the potential to reduce the annual number of new cervical cancers worldwide to roughly 150,000, from the current 500,000, and cut global deaths from the cancer by more than two-thirds, to an estimated 90,000.

But an FDA review of study results found that the vaccine may lead to an increased number of cases of a cancer precursor among patients already infected by any of the four virus types at the time they receive the vaccine.

A secondary concern is that any advantage the vaccine provides in protecting against the four virus types could be offset by infection by any of the multiple other types of HPV that the vaccine does not cover, according to the FDA documents.