The Food and Drug Administration approved GlaxoSmithKline PLC's (GSK) Cervarix vaccine designed to protect against cervical cancer in womenand expanded the approval of Merck & Co.'s (MRK) competitor vaccine Gardasil for males to protect against genital warts. Cervarix will compete against Gardasil, which was first approved for use in girls and women in 2006. Cervarix was approved for use in women ages 10 to 25 and Gardasil was approved for use in males ages nine through 26.

FDA's approval of both vaccines follows a recommendation by an outside panel of medical experts in September. Regarding Cervarix, the panel said the vaccine was safe and effective at preventing an infection that can cause cervical cancer in women as well as a precancerous condition that can lead to cervical cancer. On Gardasil, the panel also said the vaccine was safe and effective for use in males, although some panel members said they weren't sure how long the vaccine offers protection to those who receive it.

Cervarix is designed to protect against cervical cancer and other conditions linked to two strains of human papillomavirus, or HPV, a common sexually transmitted disease. Cervarix protects against HPV strains 16 and 18, which are linked to about 70% of cervical cancer cases in the U.S. Gardasil also protects against the same strains along with two others that are linked to genital warts in both men and women. There's also evidence that Cervarix protects against cancer caused by another HPV strain that is closely related to types 16 and 18.

The FDA has said that about 40 strains of HPV infect the human genital tract, and so neither Cervarix nor Gardasil protects against all HPV infection.

Glaxo first sought FDA approval for Cervarix in 2007, but the FDA said it needed more information before it would consider approving the vaccine. Glaxo refiled the application for Cervarix in March.

During last month's FDA advisory committee meeting, the agency raised concerns about a higher rate of miscarriages among females who received Cervarix and said it couldn't rule out a "small effect" on pregnancies. (Cervarix and Gardasil are not approved for use in pregnant women.)

The agency said it would require a post-marketing safety study to monitor the outcome of pregnancies in women who might receive Cervarix along with other potential safety concerns. The FDA is also requiring Merck to conduct long-term safety studies of Gardasil.

Gardasil generated $1.4 billion in sales for Merck last year, although the sales pace has slowed so far this year amid lingering questions about the vaccine's safety. Expanded approval of the vaccine could boost sales.

In August, the FDA and Centers for Disease Control and Prevention said the benefits of Gardasil outweighed its risks after a new CDC-led safety review showed higher rates of fainting and blood clots. In June, the FDA strengthened Gardasil's label to warn doctors about fainting and recommended that vaccine recipients be closely monitored for 15 minutes after receiving the vaccine.

HPV vaccines are designed to be administered before people become sexually active. In the U.S. the CDC recommends that Gardasil be offered to 11-to-12 year old girls along with other vaccines that are routinely given to that age group. Once vaccines are approved by the FDA, they are later considered by a CDC advisory panel. Private insurance companies typically wait for CDC panel endorsement of vaccines before agreeing to pay for themBoth Cervarix and Gardasil are set for consideration by the CDC panel next week.

-By Jennifer Corbett Dooren, Dow Jones Newswires; 202-862-9294; jennifer.corbett@dowjones.com