TORONTO - Females between nine and 26 should be routinely vaccinated against human papillomavirus, a sexually transmitted disease that can cause genital warts and cervical cancer, says Canada's expert advisory panel on immunization.
In recommendations released Tuesday, the National Advisory Committee on Immunization (NACI) said Canadian girls aged nine to 13 who have not yet become sexually active should be immunized with Gardasil, a vaccine that protects against four strains of human papillomavirus, or HPV.
The Canadian committee's recommendations differ somewhat from those of its American counterpart. The U.S. Advisory Committee on Immunization Practices issued guidelines in June suggesting that all 11- and 12-year-old females be routinely vaccinated against HPV, while girls as young as nine could get immunized at the discretion of their doctors.
"We recommended nine to age 13 because that's the most likely period of time before females in Canada would become sexually active,'' said Dr. Shelley Deeks, executive secretary of NACI and a senior medical specialist in the immunization and respiratory infections division at the Public Health Agency of Canada.
The committee said females aged 14 to 26 should also be vaccinated, even if they are already sexually active or have had previous Pap smear abnormalities or a previous HPV infection. However, Gardasil is not recommended for girls under age nine, for males or for pregnant women.
HPV is a common virus: an estimated 75 per cent of women will have at least one HPV infection in their lifetime. HPV causes almost all cervical cancers, killing about 290,000 women worldwide, including about 400 in Canada, each year.
Gardasil, made by Merck and Co. and approved by Health Canada last July, protects against strains that are responsible for about 70 per cent of cervical cancer and 90 per cent of genital warts.
"From an overall point of view, I think this vaccine is a great vaccine and it's a great step forward for women's health in Canada,'' Deeks said in an interview Tuesday.
The question now is whether provinces and territories will take the next step and include HPV vaccination as part of their publicly funded immunization programs, along with vaccines against such diseases as polio, measles, mumps and rubella.
Historically, Deeks said, provinces and territories have often followed the national committee's guidelines on immunization and implemented insured programs for their individual populations.
Until such programs come into force, Canadians can obtain the vaccine through their physicians, but will have to pay the cost themselves.
At the time of its approval last summer, a Merck Canada spokesman said Gardasil was expected to cost about $135 per dose, with three doses over six months needed to confer full immunity.
Deeks said the vaccine has not been approved for girls under age nine, women over 26, for males or pregnant women, primarily because clinical trials to prove safety and effectiveness in those groups have either not been conducted or are not completed.
Although girls under nine could likely be safely vaccinated against HPV, the protection might not last long enough to be worthwhile, she said.
"You want to get to women before they start sexual intercourse . . . If you vaccinate a five-year-old, the vaccine would have to be protective for years and years and years before they actually start having intercourse which puts them at risk for HPV.''
"Because we don't know the duration of protection, you want to get them relatively close to sexual debut but recognizing that sexual debut in Canada is quite difficult to pinpoint.''
Even with vaccination, NACI advises that females must continue to get regular screening for cervical cancer, since the vaccine does not protect against those strains that cause 30 per cent of the malignancies.
As for women over age 26, Deeks said studies are ongoing, so NACI cannot provide any guidelines at this time.
"But what we have said is that its use can be considered in individual circumstances,'' said Deeks, adding that women should discuss the issue with their doctors.
While the vaccine would not be harmful if someone were already infected with HPV, it probably wouldn't be protective, she said.
"There are no data that this vaccine is going to alter the course of illness if you've been infected. It's just that you may feel erroneously that you've been protected when you've already been infected.''
An expert working group, which includes members of NACI and the Canadian Immunization Committee, will be putting together recommendations on implementing HPV vaccination programs, which could be used by the provinces and territories. The group will take into consideration cost-effectiveness, public acceptability and feasibility of delivering population-based immunization programs.
The group hopes to have its report ready by the end of this year, Deeks said.
