Merck HPV Vaccine Effective in Preventing Infection With Four Strains Linked to Genital Warts, Cervical Cancer, Study Says

Main Category: Women's Health / Gynecology
Article Date: 11 Apr 2005 - 0:00 PDT

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Merck's experimental vaccine targeting the four strains of the sexually transmitted disease human papillomavirus that are most likely to cause cervical cancer or genital warts was 89% effective in preventing infection with the viral strains and 100% effective in preventing cervical cancer, precancerous lesions or genital warts, according to a study published in the April issue of the journal Lancet Oncology, Reuters Health reports. Luisa Villa, a biologist at the Ludwig Institute for Cancer Research in Sao Paulo, Brazil, and colleagues conducted the Phase II trial of the vaccine among 552 women ages 16 to 23 in the United States, Europe and Brazil. None of the participants were pregnant, had a history of abnormal Pap tests or had more than four sexual partners (Reuters Health, 4/7). Participants who had tested positive for HPV antibodies in the past were not excluded from the study. Of the 552 study participants, 277 received three shots of the vaccine -- known as Gardasil -- and 275 women received placebo injections over a six-month period (Rubin, USA Today, 4/6). Over three years, study participants underwent routine pelvic exams, Pap testing, serum testing for HPV antibodies and cervicovaginal sampling for HPV DNA (Villa et al., Lancet Oncology, 4/1).

Results
Among the women who received the placebo, 36 either contracted HPV or developed one of the diseases associated with it (Johnson, AP/Long Island Newsday, 4/6). Of those, three developed genital warts and three developed pre-cancerous cervical lesions (USA Today, 4/6). Among the women who received the vaccine, four contracted HPV, but none of them developed any of the diseases associated with the virus. Overall, the researchers found that the experimental vaccine led to approximately 90% fewer cases of persistent infection or disease due to HPV types 16 and 18, which cause about 70% of cervical cancer cases, or types 6 and 11, which cause about 90% of all cases of genital warts, AP/Newsday reports (AP/Long Island Newsday, 4/6). Although HPV antibodies dropped at the end of the study period among women who had received the experimental vaccine, their antibody levels were still higher than in women naturally infected with HPV (USA Today, 4/6).

Reaction
"It's the first time we show efficacy for the most broad-coverage vaccine in development," Eliav Barr, head of Merck's HPV vaccine development program, said (AP/Long Island Newsday, 4/6). "If (larger) Phase III studies demonstrate the vaccine is as effective as this, I'm sure that it will change the history of cervical cancer," Villa said in a phone interview (Hirschler, Reuters, 4/6). The researchers believe the vaccine would be most effective if administered to girls ages 10 to 13 because they likely would not have been exposed to the virus previously (BBC News, 4/7). Christopher Crum, director of women's and perinatology pathology at the Brigham and Women's Hospital in Boston, said he is "cautiously optimistic" that the vaccine's protective effects would last throughout a woman's reproductive years, according to USA Today (USA Today, 4/6).

Other Ongoing Trials
GlaxoSmithKline also is developing a vaccine against HPV that is being tested in thousands of women around the world to confirm the effectiveness and safety of the vaccines (Kaiser Daily Reproductive Health Report, 4/5). The newly released results of the Merck study are "almost identical" to the findings of a study testing the effectiveness of GSK's experimental HPV vaccine targeting strains 16 and 18, Reuters reports (Reuters, 4/6). Currently, the companies are competing to get their products approved. GSK plans to file for regulatory approval for its vaccine, called Cervarix, in Europe in 2006. Merck plans to apply for FDA approval for its expanded HPV vaccine in late 2005 (Kaiser Daily Reproductive Health Report, 4/5).

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