Wall Street Journal Examines Efficacy Of HPV Vaccine Gardasil In Treating Precancerous Lesions, Preventing Cervical Cancer
The Wall Street Journal on Monday examined the efficacy of Merck’s human papillomavirus vaccine Gardasil in treating precancerous lesions and preventing cervical cancer (Carreyrou, Wall Street Journal, 4/16). Gardasil in clinical trials has been shown to be 100% effective in preventing infection with strains 16 and 18, which together cause about 70% of cervical cancer cases, and about 99% effective in preventing HPV strains 6 and 11, which together with strains 16 and 18 cause about 90% of genital wart cases, among women not already infected with these strains. FDA in July 2006 approved Gardasil for sale and marketing to girls and women ages nine to 26, and CDC’s Advisory Committee on Immunization Practices later that month voted unanimously to recommend that girls ages 11 and 12 receive the vaccine (Kaiser Daily Women’s Health Policy Report, 4/5). According to the Journal, the vaccine has been “dogged by uncertainty” about “how effective it really is.” In clinical trials, 361 of 8,817 women who received at least one shot of Gardasil developed precancerous lesions on their cervixes within three years of vaccinations, only 14% fewer than women in a placebo group, the Journal reports. Merck has said the 14% figure is misleading because more than 25% of the women in the study were already infected with HPV before receiving the vaccine. In a subset of 4,616 women in the trial who were mostly free of HPV when they were vaccinated, only 52 developed precancerous lesions on their cervixes over the next three years, 46% less than women in the placebo group, according to the company. According to the Journal, the efficacy of the drug in preventing lesions is a “significant issue” because if a Pap test shows lesions, physicians will usually remove any that are seen as serious.
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While Merck has said that Gardasil prevents infection with the two strains that cause 70% of cervical cancer cases in women not already infected with those strains, Eliav Barr, head of Merck’s HPV vaccine program, said Gardasil’s true efficacy will become more apparent with time, especially in the group that includes women with a pre-existing infection. Barr said that the vaccine is less than 70% effective in preventing precancerous lesions but adds that it will eventually be shown to prevent nearly 60% of the lesions doctors would want to remove. Scott Emerson, a professor of biostatistics at the University of Washington who sat on the FDA advisory panel that recommended approval of Gardasil, said he is not convinced that the vaccine is worth the billions of dollars likely to be spent on it in the coming years. “I do believe that Gardasil protects against HPV 16 and 18, but the effect it will have on cervical cancer rates in this country is another question entirely,” Emerson said, adding, “It’s almost the treating the symptom but not the disease sort of idea” (Wall Street Journal, 4/16).
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