Gardasil, is designed to protect women against four strains of the human papillomavirus (HPV) and will go head-to-head against GlaxoSmithKline's (GSK) rival product Cervarix, which targets just the two strains responsible for cervical cancer, a disease that kills a quarter of a million women each year.
Both treatments are now in final-stage clinical studies and are tipped by industry analysts to be multibillion-dollar sellers.
Phase III clinical trials to evaluate Gardasil are already underway with over 25,000 participants enrolled worldwide, with results expected to be available later this year, and if successful Gardasil could be on the market in two years.
The vaccine, made from a non-infectious virus-like particle, was also found to be 100 per cent effective at preventing the appearance of pre-cancerous cells.
In the 227-woman study, Gardasil was able to reduce the incidence of several human papillomavirus (HPV) strains that are linked to the development of both pre-cancerous lesions and genital warts. Over two and a half years of follow-up, Gardasil reduced the combined incidence of persistent infection from HPV-6, HPV-11, HPV-16, or NPV-18 - as well as related genital disease including new cervical pre-cancers and genital warts - by 90 per cent. In absolute terms, there were 36 cases in the placebo group compared to just four among the women taking Gardasil.
HPV types 6 or 11 are not normally linked to cervical cancer, but they can cause abnormal Pap smears, which then lead to additional tests and unnecessary worries about cancer. Gardasil targets the HPV types most commonly associated with cervical cancer, as well as the types that cause genital warts and many abnormal Pap smears, to reduce the burden from HPV infection as much as possible.
"Although the study was not originally designed or powered to assess vaccine efficacy on the disease endpoints separately, efficacy of the investigational vaccine against cervical pre-cancers caused by the HPV types 16 18, 6 and 11 was 100 per cent," said Kevin Ault, department of obstetrics and gynaecology, University of Iowa Carver College of Medicine.
Cervical cancer is one of the leading causes of cancer death amongst women around the world, with approximately 470,000 new cases and 230,000 deaths every year - almost 80 per cent of which occur in developing countries. According to market research by Decision resources, the market for HPV treatments is expected to grow from $135 million dollars in 2002 to $1.4 billion (€1.08 billion) in 2012, with prophylactic vaccines driving this growth.
Six months ago, The Lancet also published a study of GSK's Cervarix vaccine, designed to protect against the HPV-16 and HPV-18 strains of the virus linked to cervical cancer. Although, this study showed a 100 per cent protection rate for the vaccine at six months it targeted just the two strains responsible for cervical cancer.
If approved, the availability of GSK's Cervarix and Merck's Gardasil could make it feasible to vaccinate young girls before they become sexually active and pick up HPV infection, although additional work needs to be done to establish safety and efficacy and crucially how long the protection will last.