But efforts to head off a rising COVID-19 wave are complicated by public pandemic fatigue.
COVID-19 case numbers are increasing as Canada's hospitals struggle to clear backlogs from months of postponed procedures.
Many burnt-out staff members appear ill-equipped for another surge in infections.
"I say very clearly: Now is not the time to travel," Health Minister Jean-Yves Duclos said at a news conference, adding that it is clear there is community transmission of Omicron in Canada.
Duclos also said the government is sending millions more COVID-19 vaccine doses and rapid tests to the 10 provinces.
Canada already has travel bans on 10 African countries because of concerns about the new variant.
In March 2020, Canada advised people not to travel abroad unless necessary but it withdrew the notice in October of this year - before the first Omicron cases were reported - citing the success of vaccination campaigns.
Peter Juni, director of Ontario's COVID-19 science advisory board, urged people to take precautions, get vaccinated and not take Omicron lightly.
"What really worries me is that people are asleep at the steering wheel, internationally," Juni said.
"They have wishful thinking it will be mild ... This is not a realistic attitude."
There is "massive vulnerability" in Canada's healthcare systems, said Andrew Morris, an infectious disease doctor in Toronto, who added it is "highly likely" they will be overwhelmed.
Provinces have been reluctant to tighten restrictions again but some communities are taking matters into their own hands.
Ontario, the country's most populous province, said this week it is "temporarily interrupting" its return-to-office plan for provincial employees.
Health officials are trying to convince the public to get third doses of COVID-19 vaccines.
Provinces including Manitoba have expanded booster doses to everyone 18 and older. Ontario, Quebec, Alberta, British Columbia and other provinces have been rolling them out more slowly, targeting older or more vulnerable people first.
Amid fears of asymptomatic COVID-19 transmission, provinces that were given millions of rapid antigen tests by the federal government have come under fire for not distributing them more widely.
Ontario promised to make two million tests available in "high-traffic" areas and to allot five per student to school children this week. Quebec will hand out five tests per person starting next week. Alberta promised to give out 500,000 starting on Friday.
British Columbia health officials said this week they had not received the tests they were hoping for from the federal government and defended providing tens of thousands of rapid tests a week to hundreds of private employers.
Meanwhile, Alberta loosened restrictions on private gatherings on Wednesday, with Premier Jason Kenney citing pandemic fatigue.
Doctor Juni said he understands people are tired of the pandemic.
"I'm completely exhausted," Juni said. "I've had it. I'm done completely. But the virus doesn't care."
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