MONTREAL -- A new blood-donation policy came into effect across Canada on Monday, officially nixing the lifelong ban that prevented men who have had sex with men from giving blood.

Canadian Blood Services and HEMA-Quebec -- which oversee Canada's blood system -- are now allowing men to donate blood if they have not had homosexual sex in the last five years.

The five-year rule is non-negotiable, even if a potential donor has had their blood screened and is perfectly healthy.

"We can't make exceptions," said Marc Plante, a CBS spokesperson.

"Those policies are there for safety reasons, and unfortunately we can't pick and choose, as much as we'd love to. We can't."

The new policy comes two decades after Canada's tainted-blood scandal.

Transfusions infected over 30,000 Canadians with Hepatitis C or HIV, sparking an inquiry in 1993 that ultimately led to the Red Cross being stripped of its control of the blood system.

The rules in effect from the 1980s until now excluded a man from giving blood, for the rest of his life, if he had ever had sex with another man since 1977 -- cited as the date HIV began spreading in developed countries.

While Health Canada approved the latest policy change in late May, there has been a delay in its implementation to allow suppliers of blood products enough time to update their means of determining donor eligibility, and to train employees.

Neither CBS or HEMA-Quebec have any sort of awareness campaign planned to notify Canadians of the new policy.

Plante said no such publicity is warranted because the new eligibility criteria is unlikely to lead to many new donors.

The criteria for blood donors varies around the globe.

In Britain and Australia, the deferral period for men who have had sex with a man is one year.

In the United States, however, men who have had sex with a man are prohibited from ever giving blood. The American Red Cross, America's Blood Centres and the AABB have jointly recommended that the ban be softened to a year-long deferral.

In 2010, the three organizations issued a joint statement that reiterated their 2006 position, and referred to the lifelong ban as "medically and scientifically unwarranted."

Policy-markers said the new five-year timeline was because of lingering concerns.

"The five-year period was decided because there were concerns by transfusion recipients, and some experts in the field of transfusion medicine, that the population of men who are having sex with men could be a risk for future unknown pathogens that would emerge, just like, for example, HIV did emerge, and did struck more specifically certain groups," said HEMA-Quebec VP Medical Affairs Marc Germain.

"That was really the basis for the longer period that was applied."

His organization estimates that the likelihood of transmitting HIV through a blood transfusion is extremely low, and will not be affected by the new policy.

It places the probability at one infection in Quebec per 30 million transfusions.

When applying to become potential donors, candidates must sign a legal form declaring that all information disclosed is true.

While the five-year deferral might be one step removed from a full ban, some critics of the new policy don't think it's an adequate upgrade.

A Canadian students' group is among them.

The Canadian Federation of Students, which represents over half a million students from over 80 post-secondary institutions across the country, has worked alongside the Canadian AIDS Society and gay-rights group EGALE Canada on its "End the Ban" campaign.

The campaign, launched in 2007, says it wants to raise awareness of, and oppose, the discrimination built into the country's blood donation process.

The CFS says that while the policy might have changed, its stance has not.

CFS Internal Coordinator Brent Farrington says the federation has been working to improve equity in blood donation since 1998.

He notes that a large amount of blood is collected on university and college campuses. While the new policy is a step forward, he says, it isn't enough.

"We still see this as a discriminatory policy that unfairly disadvantages and marginalizes men, who have had sex with men, from donating blood," he said.

"We believe there is a safer system that could exist that doesn't marginalize individuals, and also protects the blood supply."

The AIDS Community Centre in Montreal also remains unsatisfied.

"We'd like to see the donor model based on behaviour -- rather than sexual orientation or gender," said Puelo Deir, a spokesman at the centre.

"(The new policy) definitely needs improvement," he said. "This is just a small step in the right direction -- but there is still much work to do."

While HEMA-Quebec says it's considered this type of approach, they say it simply isn't feasible.

"The vast majority of experts in the field agree that (a behaviour-based approach) would not be a viable option," Germain said, pointing out that HEMA-Quebec collects upwards of 1,000 blood donations every day.

"We would have to add a considerable number of questions at the time of donor evaluation -- which might not be practical," he said.

Germain also pointed to other potential flaws in such a system. He said it would require accurate information received, in some cases, second-hand.

"(A behaviour-based) approach would also mean that information would come not only from the prospective donor, but also the current partners of that donor," Germain said.

For safety reasons, he said, HEMA-Quebec opts to rely solely on first-hand information.

Unlike some other advocacy groups, the Canadian AIDS Society supports the new policy.

"We have been pushing for change from the old, outdated, unscientific lifetime ban," said Douglas Elliott, a lawyer for the society.

"But we actually have been advocating that the initial change should be to a five-year period of celibacy."

Elliott said that while the society's position has not been too popular within the gay community, he thinks it's important to approach such a change slowly.

"More so (than other organizations) we have been willing to live with an interim change," he said.

"We recognize that you have to take baby steps, and the most important thing to do is make change in the first place."

Eventually, Elliott says the society would like to see behaviour-based criteria implemented.

"It's important to get a commitment to ongoing reform, and if we have that, we will be moving towards fewer and fewer restrictions and, before long, asking those behavioural-based questions," he said.