John Carreyou and Keith Winstein in the WSJ today (subs. req'd):
An editorial published in the New England Journal of Medicine raises questions about the overall effectiveness of Merck & Co.'s cervical-cancer vaccine, Gardasil, and advises policymakers, doctors and parents to adopt "a cautious approach" toward vaccination.The scientific consensus on this doesn't seem very settled.
The editorial accompanied a study published in the medical journal analyzing results of a clinical trial of the vaccine, which targets two types of the human papillomavirus thought to cause most cervical cancers and two other types that cause genital warts.
In their NEJM editorial, George F. Sawaya and Karen Smith-McCune, members of the department of obstetrics and gynecology at the University of California, San Francisco, wrote that "a cautious approach" toward vaccination "may be warranted in light of important unanswered questions about overall vaccine effectiveness, duration of protection, and adverse effects that may emerge over time."
The authors called the vaccine's overall efficacy against precancerous lesions of the cervix "modest" and theorized that one reason for this limited efficacy might be that other cancer-causing HPV types fill "the biological niche left behind after the elimination of HPV types 16 and 18." HPV has more than 100 different types, roughly 17 of which are thought to cause cancer.
To summarize this published medical journal article: http://content.nejm.org/cgi...
1. In the FUTURE I trial, GARDASIL demonstrated no clinical efficacy among the general subject population for overall reduction in the rates of grade 2 and grade 3 cervical intraepithelial neoplasia and adenocarcinoma -- the only recognized precursors to cervical cancer.
2. In the larger FUTURE II trial, GARDASIL demonstrated no clinical efficacy among the general subject population for overall reduction in the rates of grade 3 cervical intraepithelial neoplasia and adenocarcinoma -- the strongest (and many would argue only valid) precursors to cervical cancer.
3. Extrapolating from GARDASIL's very limited clinical "success" (in the FUTURE II study only) against grade 2 cervical dysplasias (40% of which regress spontaneously), 129 women would be have to be vaccinated (at a cost of about $60,000) to prevent a single grade 2 cervical dysplasia.
4. GARDASIL's protection against cancer associated HPV strains 16 and 18 appears to cause a disproportionate increase in of pre-cancerous dysplasias associated with other HPV strains associated with cervical cancer "raising the possibility that other oncogenic HPV types eventually filled the biologic niche left behind after the elimination of HPV types 16 and 18."
5. Even if you segregate out the women who hadn't been previously exposed to either HPV 16 or 18, we are talking about just a 17% decrease in all high grade dysplasias (266 out of 6080 vs. 219 out of 6087) -- many of which would spontaneously regress without treatment. So we would have vaccinate 129 women (at about $500 for the three shot regimen) to avoid a single, eminently treatable dysplasia. That's about $60,000 per dysplasia prevented.
This is all directly from the article: http://content.nejm.org/cgi...
I myself would add that we currently have only 3 years of follow up to go on in terms of both GARDASIL's safety and efficacy among the 16 to 26 year female population, no data concerning its efficacy among 9 to 12 year old girls and only 18 months of follow up on less than 600 total preteen girls in terms of safety data about GARDASIL within its targeted population.
Posted by mhatrw @ 05/12/07 01:45 PM
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