US conservatives block cancer vaccine for girls - 14 May 2007 - New Scientist
Plans to vaccinate young girls against the sexually-transmitted virus that causes cervical cancer have been blocked in several US states by conservative groups, who say that doing so would encourage promiscuity.
Advocates of the vaccine point out that the jabs work against human papillomavirus (HPV) - which causes virtually all cases of cervical cancer - and are safe.
The latest data from a large clinical trial of Merck’s cervical cancer vaccine, Gardasil, found it offered 100% protection against cervical, vulval and vaginal diseases, caused by HPV (types 6, 11, 16 and 18) and 98% protection against advanced pre-cancers caused by HPV types 16 and 18 (New England Journal of Medicine: vol 356, p1915).
After around three years of the four-year trial, almost all girls who received the vaccine before being exposed to HPV 16 or 18 appear to be protected. Those who had already been exposed to the viruses received little benefit, but by vaccinating early on, perhaps at 11 years of age, most girls could be protected.
Controversial care
However, the introduction of a vaccine against HPV types 16 and 18, which together cause 70% of cervical cancer cases, has been dogged by arguments. Some conservative groups complain that by cutting the risk of catching a sexually-transmitted disease, the vaccine would encourage sexual activity in young girls.
Earlier data from the same trial had already led the US Centers for Disease Control and Protection (CDC) to recommend that 11-12 year-olds be vaccinated.
However, attempts to introduce vaccination programmes at the state level have run up against opposition. Four states – West Virginia, Kentucky, Mississippi and New Mexico – have rejected vaccine programmes.
The new results, which include extra data showing a lack of side effects, could influence the debate in the 15 states where legislation is still on the table.
Premature reaction?
Public health experts are also divided, though. Some question whether the relatively small numbers of lives that would be saved are justified by the significant cost of a vaccine programme. Merck will charge around $360 for the three-doses needed.
George Sawaya, a gynaecologist at the Comprehensive Cancer Center at the University of California, San Francisco, notes that the trial still has another year to run. Surprises often appear late on in such studies and Sawaya says he thinks the CDC should have waited until all the data was available before taking a stance on the vaccine.
The trial’s impact may be better felt in developing nations, where the screening programmes that have already cut deaths in richer countries are often too expensive to implement.
The GAVI Alliance, a public-private partnership that spends around $300 million annually on vaccination programmes in poor countries, is considering funding HPV shots.
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To summarize this published medical journal article:
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 linked above.
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.
14 May 07 at 9:59 p #