The HPV vaccine provides 100 per cent protection against vulval and vaginal disease caused by four strains of the virus among women who were not already infected, finds a new study published in The Lancet journal.
For the study, more than 18,000 women between the ages of 16 to 26 participated in three trials in 24 countries across Europe, Asia, and the Americas. They received three doses of either the human papillomavirus (HPV) vaccines or the placebo.
The women were then followed up for an average of three years.
Vaccine efficacy varied from 71 per cent in women previously exposed to HPV, to 100 per cent in those not previously exposed.
The findings seem to confirm that HPV, which is responsible for virtually all cases of cervical cancer, is also responsible for many cases of vulval and vaginal cancer.
On average, 436 Canadian women are newly diagnosed with vulvar or vaginal cancer each year. Approximately 128 women die from their disease. HPV is responsible for roughly 80 per cent of these cases.
Tumours in the vulva and vagina are still a rare finding. Nevertheless, Canada has among the highest reported rates of vulvar cancer in the world. Worldwide, there has been a striking increase of high-grade vulval pre-cancer lesions and cancer over the past 30 years.
"This trend is worrying," the authors say, "because these cancers are not amenable to a screening programme.
They conclude: "In summary, these combined studies provide substantial evidence that a quadrivalent HPV L1 VLP vaccine is highly effective in preventing high-grade vulval and vaginal lesions associated with HPV16 or HPV18. The maximum effect of vaccination is expected in girls who are vaccinated in early adolescence, before exposure.
"This intervention could greatly reduce the morbidity, mortality and health-care costs associated with these diseases."
The HPV vaccine is sold in Canada under the name Gardasil and was approved by Health Canada in July 2006. The vaccine is indicated for the prevention of cervical cancer, vulvar cancer, vaginal cancer, precancerous lesions at these sites and genital warts caused by HPV 6, 11, 16 and 18.
HPV types 16 and 18 account for 70 per cent of cervical cancer cases and types 6 and 11 cause about 90 per cent of cases of genital warts. All four types cause a large number of "abnormal" Pap test results and low-grade cervical lesions.
In January 2007, the National Advisory Committee on Immunization (NACI) recommended that all Canadian girls and women aged 9 to 26 be routinely vaccinated.
The federal government recently made available $300 million to the provinces and territories to support the launch of HPV vaccination programs.
