Merck Vaccine Could Reduce Risk of Cervical Cancer, Study Says
None of the women who received Merck's experimental vaccine against the most common strain of the sexually transmitted disease human papillomavirus developed lesions that are a precursor to cervical cancer, according to a study presented on Monday in Washington, D.C., at the Interscience Conference on Antimicrobial Agents and Chemotherapy, the annual meeting of the American Society for Microbiology, USA Today reports (Manning, USA Today, 11/2). Connie Mao and colleagues from the University of Washington-Seattle and four other universities studied 1,505 women ages 16 to 23 for six years. Researchers administered the experimental vaccine for HPV type 16 -- which infects 20% of people in the United States and causes about 50% of all cervical cancer cases -- to 755 women and gave 750 women a placebo. Both groups were given shots of either the vaccine or the placebo three times over six months.
After an average of four years, none of the vaccinated women had developed the precancerous lesions that are a precursor to cervical cancer, and seven had contracted HPV 16. Among the women who received the placebo, 12 had developed precancerous lesions and 111 had contracted HPV 16. Therefore, researchers concluded that the experimental vaccine was 94% effective in protecting women from HPV 16 infection and 100% effective in protecting women from precancerous cervical lesions over four years.
Researchers said that the vaccine would be recommended as a preventive measure and given to girls and young women before they become sexually active, the Philadelphia Inquirer reports. However, the vaccine would not eliminate the need for Pap tests to screen for cervical cancer, especially because the vaccine does not prevent every type of HPV that causes the disease, according to the Inquirer (Loyd, Philadelphia Inquirer, 11/2).
Currently, about 15,000 U.S. women develop cervical cancer each year, one-third of whom die from the disease, and the disease kills more than 230,000 women worldwide annually, the Los Angeles Times reports (Maugh, Los Angeles Times, 11/2).
Merck also is in the final stages of testing an expanded vaccine would protect against both HPV 16 and HPV 18 -- which causes an additional 10% to 20% of cervical cancers -- as well as other HPV strains that cause genital warts in men and women, and penile and anal cancers in men, the AP/Albany Times Union reports. The study includes about 25,000 men and women in 34 countries, and results are expected in 2005 (Marchione, AP/Albany Times Union, 11/2).
Merck plans to apply for FDA approval for its expanded vaccine in late 2005. Merck also is planning long-term studies to determine if and when booster shots may be necessary to maintain immunity, according to the Inquirer. The new results put Merck about a year ahead of pharmaceutical company GlaxoSmithKline, which also is working on a vaccine to prevent cervical cancer, according to the Inquirer (Philadelphia Inquirer, 11/2).
Christopher Crum, director of women's and perinatal pathology at Brigham and Women's Hospital in Boston called the study a "huge discovery," adding, "If placed into practice, it should have a tremendous impact." Kenneth Noller, chair of the OB/GYN department at Tufts-New England Medical Center said that the results were "promising" but added that there are still many "unknowns" and that further research is required to determine how long the vaccine protection lasts (Philadelphia Inquirer, 11/2).
"We're thrilled about the results," Dr. Eliav Barr, who leads the development of the vaccine for Merck, said, adding, "The immune responses seem to be really long-lasting" (AP/Albany Times Union, 11/2). Crum said that a major challenge would be delivering the vaccine to women in developing nations who need it the most, according to the Inquirer. Barr said that Merck is in discussions with groups such as the World Health Organization to make HPV vaccines available in developing countries (Philadelphia Inquirer, 11/2). "This is a very important issue for women's health around the world," Dr. Scott Hammer, an infectious disease expert at Columbia University, said (AP/Albany Times Union, 11/2).