An experimental vaccine to prevent the most common forms of cervical cancer proved 100 percent effective in a two-year test on more than 10,000 girls and women, drug maker Merck &Co. said Thursday.
“I see this as a phenomenal breakthrough,” said Dr. Gloria Bachmann, director of the Women’s Health Institute at Robert Wood Johnson Medical School in New Brunswick, N.J.
Worldwide, cervical cancer is one of the most common cancers among women. It kills nearly 300,000 people a year, including about 3,700 in the United States.
Merck is hoping to win Food and Drug Administration approval for the vaccine, Gardasil, and put it on the market as soon as late 2006. It would be the first vaccine to prevent cervical cancer, a disease caused almost exclusively by a highly common sexually transmitted virus called the human papilloma virus, or HPV.
The study, which was funded by Merck, will be presented today at a meeting of the Infectious Diseases Society of America.
About 20 million Americans have some form of HPV, which in addition to cervical cancer can cause painful genital warts.
Doctors expect the vaccine to be routinely offered to girls – and boys, too, because they can spread the virus to their partners – before they become sexually active, though the practice is certain to run into opposition from conservatives and religious groups.
The genetically engineered vaccine prevents cervical cancer by blocking infection from the two strains of HPV that cause 70 percent of all cases of the disease.
The study included 10,559 sexually active women ages 16 to 26 in the United States and 12 other countries who were not infected with either of the two virus strains, called HPV 16 and 18. Half got three vaccine doses over six months; half got dummy shots.
Among those still virus-free after the six months, none of those who received the vaccine developed either cervical cancer or precancerous lesions during two years of follow-up, compared with 21 of those who got dummy shots.
“To have 100 percent efficacy is something that you have very rarely,” said Dr. Eliav Barr, Merck’s head of clinical development for the vaccine. “We’re breaking out the champagne.”
A second analysis showed that after just one dose, the vaccine was 97 percent effective. Barr said the 97 percent rate was more “real world,” given that patients sometimes miss or delay follow-up shots.
Bachmann said that to fight the disease, students would have to be vaccinated in high school, middle school, even elementary school, before they become sexually active.
The Merck vaccine was also found to reduce infection from two other HPV strains that cause 90 percent of genital warts.
Merck, hammered by slumping profits and facing about 5,000 lawsuits over its withdrawn painkiller Vioxx, is seeking to beat rival drug maker GlaxoSmithKline to market with the first cervical cancer vaccine.
GlaxoSmithKline is still enrolling patients in final-stage tests to determine whether its vaccine prevents cancer. It does not expect to have initial data until late in 2006.
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