NEW YORK (CNNMoney.com) - Federal regulators approved Gardasil, the first vaccine meant to prevent cervical cancer, the drugmaker Merck said Thursday.

Gardasil, a once-controversial vaccine, could reap billions of dollars in annual sales for New Jersey-based Merck, the nation's No. 2 drugmaker.

Gardasil, which works by preventing the sexually transmitted human papilloma virus (HPV) that causes cervical cancer, was approved for use in 9- to 26-year-old girls and women, the drugmaker said.

The drug was 100 percent effective in preventing strains of HPV that cause 70 percent of cervical cancer cases, and in preventing 90 percent of vaginal lesions, including genital warts, the company said.

"These are the four most medically important types [of HPV,]" said Dr. Kevin Ault of Emory University School of Medicine, who lead one of the trials. "Two of the types - 16 and 18 - are responsible for about 70 percent of cervical cancer and then the other two - six and 11 - are responsible for about 90 percent genital warts."

The vaccine is expected to be available this summer, according to Merck (down $0.03 to $33.93, Research). Analyst estimates for annual sales range from $1.6 billion to $4 billion, with the high estimate assuming that some states will require mandatory vaccination.

Gardasil is most effective as a preventative measure when used in children years before they become sexually active.

Controversy regarding the delicate topic of teenage sexuality surrounded the vaccine last year, but religious groups recently spoke in support of Gardasil, acknowledging its life-saving potential.

Gardasil faces a competition-free market, for now. But GlaxoSmithKline (down $1.04 to $54.96, Research) is developing a similar vaccine called Cervarix, which is in the last stages of study. GlaxoSmithKline's Brian Lortie, who is vice president of world wide operations for Cervarix, expects to file the vaccine to the Food and Drug Administration this year, and said it could be on the market in 2007.

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