A drug that's already on the market in this country to treat patients who have HIV might end up decreasing infection rates, now that Health Canada has approved it as a medication to prevent the virus.

Dr. Isaac Bogoch, an infectious disease specialist at Toronto General Hospital, has been prescribing Truvada as a preventative drug for years. He said the idea that other doctors will be using Truvada the same way he does is welcome news.

Truvada is a brand name for a pill that combines two medications — emtricitabine and tenofovir disoproxil fumarate. Those, in general terms, work to stop HIV from multiplying in humans. The doctor estimates it is 85 to 99 per cent effective. And if people use it with condoms, effectiveness increases.

Bogoch has been administering it "off-label" — for different uses than its original intent — for years. But that meant it was not covered by most insurance plans.

Because of this approval, insurance companies and provinces could cover costs, which can range from $12,000 to $15,000 per year.

Based on his clinic, Bogoch said the groups who will be most likely to benefit from the drug are intravenous drug users, those who engage in unprotected sex and sex workers.

It all began in 2011, when studies showed the drug was effective as prevention as well as treatment. In 2012, the U.S. approved it for its preventative qualities. Canada's approval came on Friday.

HIV rates in Canada have levelled out, said the doctor. But steady is not as good as declining, so there's work to be done.

"This drug could get us there," he said.