U.S. researchers have successfully tested a vaccine to prevent cervical cancer, the second most common cancer in women around the world after breast cancer. Such a vaccine could eventually prevent hundreds of thousands of deaths each year.
The experimental Merck Laboratories vaccine immunizes against the human papillomavirus, which infects one-fifth of adults globally. While most infections are benign, some cause cancer of the cervix, the opening to the uterus. The World Health Organization says cervical cancer hits 500,000 women annually. Most of the 300,000 women who die from it each year are in developing countries.
According to a New England Journal of Medicine study, the vaccine was effective in all 1,200 young women across the United States who received it. After 18 months, there were no papillomavirus infections among them and no precancerous lesions linked to the virus.
But there were 41 infections and nine pre-cancerous lesions among an equal number of women receiving placebo.
The inoculated women built up almost 60 times the concentration of virus-fighting antibodies seen in naturally infected women.
"This will provide us with a simple way of preventing the development of cervical cancer, " explained University of Washington physician Nancy Kiviat. She is one of dozens of scientists involved in the study. "This will be extremely important, especially for resource-poor areas where Pap screening, which in developed countries has been used to prevent cervical cancer, but in resource-poor settings, Pap screening is not feasible because of the cost and the lack of infrastructure," she added.
Pap screening is a technique in which cells from the lining of the cervix are removed with a spatula and examined under a microscope for abnormalities such as cancer or precancerous changes. Physician Christopher Crum of Brigham and Women's Hospital in Boston says a vaccine means fewer of these tests would be needed in the industrial countries, saving them substantial health care costs.
"If the vaccine were to work, you would see a reduction in abnormal Pap smears, a reduction in cancers, and you would see a redefinition of cervical cancer risk and very likely the way in which it would be managed."
For experimental purposes, the vaccine used only a single papillomavirus strain linked to least half of all cervical cancers. Dr. Crum says that if women were to be vaccinated against all types associated with the disease before becoming sexually active, the risk of cervical cancer would drop at least 85 percent.
"There are as many as 15 or 20 papillomaviruses that can cause cervical cancer," he said. "But most of these cancers fall under the purview of just a few viruses. Thus, it might be possible some time in the future to tailor a vaccine which might cover a significant proportion of those associated with cervical cancer."
Such a vaccine could also stop other harm done by the virus, including genital warts in both men and women and rare forms of penile, anal, vaginal and oral cancer. Researchers say the vaccine might also be taken by men to keep them from infecting their female partners.
If successful, a papillomavirus vaccine would be the second against a major human cancer. The other is hepatitis B vaccine, which prevents primary liver cancer.
Another study in The New England Journal of Medicine holds promise for a vaccine against a virus that causes genital herpes.
Transmitted sexually or by other skin contact, the organism infects one-fifth of adults. Although not cancer-causing, it can lead to periodic outbreaks of uncomfortable blisters or ulcers around the genitals. It can also cause devastating illness in babies born to infected women.
The new study conducted in the United States, Belgium, and Australia shows the herpes vaccine prevented disease in three-fourths of the women who received it. Curiously, it had no clear effect on men.