Ontario's health minister is urging all at-risk people in the province to get an H1N1 flu shot this week. (Canadian Press)

People in high-risk groups should get their H1N1 flu shots as soon as possible, while others should wait until next week to start getting theirs, Ontario Health Minister Deb Matthews said Monday.

Vaccinations are crucial, she said, to ensuring the pandemic doesn't turn disastrous.

"We know H1N1 is coming, it's already here and is coming even more," Matthews said.

"So we need to get people vaccinated to prevent the pandemic from taking the kind of toll we know it will take if people don't participate in the vaccination program."

Matthews made the comments in a Toronto hospital emergency department as the first shots were given to front-line health-care workers, one of the high-risk groups.

The first day of the province's vaccination program came as part of a national effort to curtail the spread of the swine flu.

"There was no pain whatsoever," said Dr. Bob Bell, CEO of the University Health Network and a surgeon, who rolled up his sleeve at the Toronto General Hospital.

"And there's a chocolate bar to follow."

Others at risk include those with chronic health conditions, as well as children between about six months and five years of age.

Ontario has enough vaccine to ensure everyone who wants or needs it will be able to get it — roughly 75 per cent of the population, the minister said.

The challenge, she said, was "getting people to roll up their sleeves" and get the shot.

The province received 722,000 doses last week with another million units expected by Tuesday.

Some family doctors will have the vaccine on hand, but local public-health units, which are distributing the vaccinations, would have a better sense of where the shots would be most readily available.

Ontario has estimated the cost of fighting H1N1 at up to $650 million.

Matthews said the vaccine has been through rigorous testing and has scientific backing for its widespread use.

"Listen to the experts," Matthews said. "The vaccination is absolutely safe."

Matthews urged pregnant women to speak to their doctors but a special unboosted formulation of the vaccine for them — 200,000 doses — was being sent from Australia to Canada and would likely arrive next week.

Dr. David Butler-Jones, Canada's chief public health officer, said the unboosted or unadjuvanted vaccine was being provided as an option to the regular vaccine, which was considered safe for pregnant women.

Matthews said pregnant women need to consider how much of a risk they face of contracting H1N1, their general health as well as how far along they are in their pregnancies before making the risk-reward analysis of whether to get the shot.