EDMONTON - Alberta's six Catholic bishops are urging parents to learn more about a vaccine that protects against cervical cancer before deciding whether their daughters should be immunized.

"There is no general consensus that the HPV vaccination is the most prudent strategy in terms of allocating health-care resources aimed at preventing deaths from cervical cancer," says a statement from the bishops released Monday.

The Alberta government recently announced that the HPV vaccine will be offered to Grade 5 girls beginning in September and to Grade 9 girls starting next year -- but only with parental consent.

In Alberta, roughly 40 women die from cervical cancer every year. But the HPV vaccine has become an issue of debate for Catholics everywhere because the human papilloma virus is sexually transmitted, so girls must be sexually active to become infected.

At least one Catholic school district in Ontario voted narrowly to no longer allow the shots on school premises.

Earlier this month, a church official in the Edmonton archdiocese spoke strongly against parents approving their daughters' participation in the vaccination program, saying that would be tacit approval of premarital sex.

The release Monday cautions Alberta's 900,000 Catholics to be aware of what are called the vaccine's limitations.

A church spokeswoman points out that Health Canada's website says the vaccine protects against 70 per cent of cervical cancers and the initial vaccination may only last five years.

The release does add that the vaccine has raised ethical questions because the unintended message is that casual sex by students "is to be expected."

"Casual or recreational sexual activity carries with it profound risks to a young person's spiritual, emotional, moral and physical health," say the bishops.

"At best, a vaccine can only be potentially effective against one of these risks - to physical health."

Alberta's Catholic church has taken the position that there may be more effective ways to prevent cervical cancer rather than through the use of the vaccine, which was only recently approved for use in Canada.

Archbishop Richard Smith of the Edmonton Archdiocese was travelling home from a conference in Quebec on Monday and was not available for comment.

The Canadian Women's Health Network has suggested a Pap smear may be a better choice to screen for cervical cancer until more is known about the long-term effects and duration of the vaccine.

An article published in the Canadian Medical Association Journal has also raised questions and suggests Pap tests as an alternative until more is known about the vaccine's effectiveness.

"A sufficient number of unanswered questions lead us to conclude that a universal immunization program ... could possibly have unintended negative consequences," says the article published last August.

Alberta will spend up to $20 million annually vaccinating roughly 40,000 girls in each of the next three years.

Alberta Health spokesman Shannon Haggerty offered a cautious response to the release from the bishops.

"It's a decision that was made with scientific evidence," said Haggerty. "But it's really up to the schools and the parents to make a decision on the vaccine because it's a voluntary program."

Catholic school boards in Edmonton and Calgary say they have decided to participate in the vaccination program, but will forward information to parents to help them "make an informed decision."