Monday is the deadline for many health-care workers to choose between the needle and the mask.

Under a new mandatory vaccination policy, healthcare workers in British Columbia, as well as several hospitals in Ontario, must get a flu shot or be forced to wear a mask while working with patients.

Dr. Douglas Sinclair, the chief medical officer of St. Michael’s Hospital in Toronto, told CTV News the decision will save lives.

“There is lots of literature on this,” said Sinclair. “Especially our frail elderly patients.”

Young, healthy workers might not become seriously ill when they contract the virus, Sinclair said. But when the virus is transferred to more vulnerable patients, serious complications such as heart failure and lung disease can occur.

St. Michael’s sees a vaccination rate of about 50 per cent at best among its workers, Sinclair said, so making staff choose between inoculation and wearing a mask should boost that number.

But while medical experts generally agree that the influenza vaccine is the most effective way to avoid getting the flu, some members of the community don’t agree with forcing the vaccine upon workers.

Dr. Michael Gardam said he used to be in favour of mandatory flu shots, but changed his tune after he began investigating the literature.

“I actually was quite alarmed,” the infectious diseases specialist said. “The support for vaccine versus mask policies is not nearly as robust as we’re being led to believe. And that really started to worry me.”

The virus doesn’t spread unless symptoms are present, Gardam said, so forcing workers to wear a mask while they appear healthy is “not doing anything.”

“A far more intelligent policy…would be simply, if you’ve got influenza-like illness, stay home until you’re better,” he said. “If you have to come to work, wear a mask while you’re at work, wash your hands a lot, and then get the heck out of there when you’re done.”

But despite objections from some prominent members of the healthcare community, the province of B.C. and hospitals like St. Michael’s, Mount Sinai and Sunnybrook in Toronto are adopting the policy.

Sinclair said that when it came down to making the decision, the evidence seemed to be there.

“In medicine, we love to debate evidence. Our sense is there is enough evidence to move ahead with this,” Sinclair said. “Because we do feel the flu vaccine isn’t perfect, but we know that the vaccination does reduce the rates of flu.”

And while Gardam and others agree that the flu vaccine is a good thing, they’re not convinced the policy will have an equally positive effect if it’s forced on healthcare workers.

“We are universally pro-flu-vaccine, we get our flu vaccines, but we definitely draw the line at the mandatory vaccine versus mask policies,” Gardam said. “Because we don’t believe it’s going to protect patients one iota and we’re burning our bridges with our staff in the same process.”

With a report from CTV News' Medical Correspondent Avis Favaro and Senior Producer Elizabeth St. Philip