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Human Papillomavirus Vaccine 100% Effective Against Major Cancer-Causing Strains: Presented at IDSA

By Ed Susman

SAN FRANCISCO, CA -- October 7, 2005 -- An experimental vaccine was completely successful in protecting women against precancerous or noninvasive cervical cancer caused by human papillomavirus (HPV) types 16 and 18 -- the major microbes that cause cervical malignancies.

The Merck & Co. quadrivalent recombinant vaccine, now known as Gardasil, protected all the women who properly took the 3 doses of the vaccine -- an initial dose followed by a dose at 2 months and at 6 months.

That cohort, which underwent 17 months of observation, included 5301 women who were 16 to 26 years of age and were recruited at 90 research sites in 13 countries. By contrast, among the 5258 women who were inoculated with a placebo vaccine and were adherent to the same schedule, 21 were found to have high-grade precancerous cervical lesions or noninvasive cancer.

The difference in protection was statistically significant at the P < .001 level, said principal researcher Laura Koutsky, PhD, professor of epidemiology, University of Washington, Seattle, Washington.

"These are the first pivotal data to show that vaccination with Gardasil reduced HPV-16- and 18-related cervical precancer and noninvasive cervical cancer," she said.

Merck is expected to file for approval of the vaccine with the US Food and Drug Administration in December.

In a presentation scheduled for today, October 7^th at the 43^rd Annual Meeting of the Infectious Diseases Society of America (IDSA), Dr. Koutsky will show that the phase 3 studies of the vaccine also demonstrated that partial compliance with the vaccine protocol was also highly protective.

Among the 5736 women -- a group that included those who missed some of the inoculations or who were not inoculated according to schedule -- 1 case developed high-grade precancerous lesion or noninvasive cancer compared with 36 such cases among the women in the placebo arm of the trial. This difference represented a 97% reduction, according to the researchers.

There were no discontinuations due to serious vaccine-related adverse events. Adverse events were higher among subjects who received Gardasil compared with placebo recipients, and the most common were injection site reactions, Dr. Koutsky said.

Approximately 20 million American men and women are infected with HPV. HPV types 16 and 18 are responsible for about 70% of all cervical cancer cases. HPV types 6 and 11, also part of the quadrivalent vaccine, are responsible for 90% of cases of genital warts.

The study evaluated the incidence of cervical intraepithelial neoplasia grade 2/3. Grade 2 is a moderate-grade lesion; grade 3 includes high-grade and carcinoma in situ lesions. It also evaluated the incidence of adenocarcinoma in situ. Cervical intraepithelial neoplasia 3 and adenocarcinoma in situ are both defined as stage 0 cancers by the International Federation of Gynecology and Obstetrics.

[Presentation title: Prophylactic Quadrivalent Human Papillomavirus (Types 6, 11, 16, 18) L1 Virus-Like Particle Vaccine (Gardasil) Reduces Cervical Intraepithelial Neoplasia 2/3 Risk. Abstract LB-8a]

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