A Toronto school board is set to vote on whether to allow public health nurses to give its young students a vaccine against HPV, a common sexually transmitted disease linked to cervical cancer.

The Ontario government is offering the human papilloma virus vaccine to all Grade 8 girls, but some catholic school boards have questioned whether the program promotes sexual activity among teens.

Late Tuesday night, the Halton Catholic District School Board narrowly voted to approve use of the vaccine.

But Ontario's Huron-Superior Catholic District School Board has already instituted a ban on the program, and the Toronto District Catholic School Board is expected to vote on the issue Wednesday.

Toronto board chair Oliver Carroll said "you can't bury your head in the sand," and said the vaccines are not a green light for premarital sex.

"I will leave it to the parents and the daughter to sort out their ethics, but in the meantime I believe we have an obligation to give them the protection they may need," he said.

A letter from Ontario's conference of Bishops had urged the Halton board not to make the vaccine available to its students on religious grounds.

"Infection with HPV or other sexually transmitted diseases can occur only through sexual activity, which carries with it profound risks to a young person's spiritual, emotional, moral and physical health," they wrote.

"The Bishops note that, at best, a vaccine can only be potentially effective against one of these risks, that to physical health, and may have other unintended and unwanted consequences."

The HPV vaccine is effective against 70 per cent of cervical cancers. And according estimates by the Canadian Cancer Society, 1,350 women will be diagnosed with cervical cancer this year in Canada and 390 will die of the disease.

Health Canada estimates that up to 75 per cent of sexually active Canadians will have at least one HPV infection in their lifetime.

Ontario Premier Dalton McGuinty said the Halton and Toronto board's reluctance to vaccinate its students shows an emerging ideological division in Ontario's public education system.

But he said the vaccines could still be given to students through the public health system.

"Ultimately ... we're going to deliver this through public health,'' he said Tuesday in Crosby, Ont. "I think in an ideal world, we'd rather do it through the schools because it's simpler and more convenient for parents and for kids.

"But, you know, if we run into a lot of resistance from a particular school board, we can -- we've already thought this through -- we can do it through public health."

Progressive Conservative Leader John Tory, currently campaigning against McGuinty for the October 10 election, said the school board should take advantage of the free vaccine program.

"I would like to hope all school boards will co-operate in making sure these vaccines are available and that if there is anybody who doesn't want to have the vaccine, that's a parental decision as opposed to a school board decision," he said in Belleville, Ont.

With a report by CTV's Lisa LaFlamme and files from The Canadian Press