Thousands of people waited in line for hours to receive their H1N1 flu vaccine at the North York Civic Centre in Toronto on Thursday. (Nathan Denette/Canadian Press)

Ontario's public health agencies will open more H1N1 vaccination clinics and expand their hours to keep up with overwhelming demand, even as the federal government warns there will be less of the serum to go around next week.

Dr. Arlene King, the province's chief medical health officer, told a news conference Thursday that local public health agencies "will continue to open more clinics and expand their operations to immunize more people" in the coming week.

"And this, of course, will be commensurate with the supply of vaccine that we get. So we're trying to match demand, need and supply," she said.

King conceded the province does not currently have enough vaccine for everyone who needs it.

"There is plenty of vaccine for those who are in our priority groups, and we will not generally be turning people away who come, but we would really ask the public to honour the priority group list and to come forward right now, this week at least," she said.

There will be enough vaccine for all Ontario residents in the future, she said.

'Significantly less vaccine'

But how quickly the vaccine will be administered is now unclear — hours after King's announcement, the federal government was telling provinces there would less vaccine available next week than originally expected.

"The federal government is advising all provinces, including Manitoba, that there will be significantly less vaccine delivered than had been anticipated in the weeks ahead," said a release posted on the Manitoba health ministry's website.

The CBC's Rosemary Barton, reporting from Ottawa, said the government will receive only 400,000 doses of the vaccine next week, a steep drop from the two million doses it received this week.

Dr. David Butler Jones, Canada's chief public health officer, laid the blame for the dropoff on a form of the vaccine meant primarily for pregnant women.

Vaccines that are currently being administered contain adjuvant, a substance that boosts immune response to the serum. Due to a dearth of evidence on the safety of adjuvant for pregnant women, Canada has ordered a separate batch of vaccines without the booster.

But the vaccine producers, Glaxo SmithKline Inc., had to shut down production of the adjuvanted version while producing the unajuvanted vaccine, Barton said. That delay in production has led directly to next week's reduced vaccine levels.

But the government maintains that it will still get all 50 million doses it ordered in eight to 12 weeks.

Clinics opened across Ontario this week, targeting health-care workers and people in priority groups. They have already had to turn thousands of people away as demand far exceeded health officials' expectations.

Public health units are distributing the vaccine as fast as they are receiving it, King said.

More than 1.4 million doses have been distributed to local public health units, said Health Minister Deb Matthews, who was also at the news conference. An additional 750,000 doses will be delivered to health units by the weekend, she said.

Initially, health officials were concerned not enough people would turn out to get vaccinated, Matthews said. As well, Telehealth Ontario is fielding five times the volume of calls it normally receives, she said.

Government response 'unacceptable'

Earlier Thursday, Matthews urged those who feel ill to assess themselves using a questionnaire on the health ministry's website, a plea made in part to help ease the call volume at Telehealth.

NDP Leader Andrea Horwath slammed the government for not being prepared for the huge demand.

"They dropped the ball in a big way. They dropped the ball … in terms of their communication plan, which resulted in people flocking to these clinics and the workers there [are] being inundated," Horwath said.

"They also dropped the ball with telecare — they didn't anticipate the increased demand on that service. And now what does the minister say? Enter our website and do a self-evaluation. That is unacceptable."

Matthews denied the government is ill-prepared.

"[These are] early days. We are a week ahead of schedule. We've got the vaccine out into tens of thousands of Ontarians today," she said.

"We're responding in real time."