In what is hailed as a public health breakthrough, a pharmaceutical company reported yesterday that an injected vaccine can prevent the vast majority of cervical cancer cases.
The vaccine, which Merck & Co. will soon submit to the Food and Drug Administration for approval, works by arming the immune system against sexually transmitted viruses that trigger the cancer.
Known as Gardasil, it would be only the second vaccine to prevent cancer. The other guards against hepatitis B infections, a leading cause of liver cancer in Asia but not the United States.
In a trial that involved 12,000 sexually active women in the United States and 12 other countries, the company reported that Gardasil was 100 percent effective in preventing cancers and pre-cancerous growths caused by two types of the so-called human papillomavirus (HPV). Together, those types account for about 70 percent of cervical cancers worldwide, experts say.
The company followed its test subjects for an average of two years, and it plans to continue monitoring the women for years to see whether their immunity remains strong.
"I think it's tremendously big - a major advance in terms of protection against papillomavirus and disease," said Dr. Raphael P. Viscidi, an HPV researcher at the Johns Hopkins School of Medicine who was not involved in the study.
"I think it will completely change the clinical practice with regard to HPV infections," he said. "The generation of women who have access to this vaccine will probably have a vanishingly small risk for cervical cancer."
As the cancer risk falls, many women would be spared costly and bothersome biopsies, surgeries and medical treatments, he said.
The vaccine is also designed to prevent two other types of HPV associated with genital warts. These growths, which are at times painful and disfiguring, do not normally turn cancerous. The company plans to report the vaccine's effectiveness against genital warts later this year.
In the coming weeks, Merck officials said, they plan to ask the FDA for permission to market the vaccine commercially.
Cervical cancer is not very common in the United States, with 10,000 new cases diagnosed annually and 3,000 deaths attributed to it. Deaths have dropped off drastically because of routine Pap smears, a test that detects precancerous cells that can be surgically removed.
