TORONTO - The window of opportunity for accelerating the pandemic flu vaccination program in Canada may be starting to close, unless word of a change of plans comes soon, experts suggested Tuesday.

But despite pressure to speed up the start of the program, the country's chief public health officer continued to insist that the projected start date of early November is still the target.

The early November start will allow Health Canada to follow the regulatory process it set out for approving the pandemic vaccine, Dr. David Butler-Jones said Tuesday.

Butler-Jones had recently said that if the risks of waiting to November started to outweigh the benefits of following the established regulatory pathway, the vaccination program could be brought forward a bit.

"(But) we're now into October ... (and) we're not seeing any of those conditions being met," Butler-Jones said in an interview with The Canadian Press.

"So at this point I'm anticipating that the regular regulatory process with a target that we can start immunizing by the first week of November, that that should all roll out fine."

With that point approaching, provinces and territories need to know when they will start taking possession of vaccine so they can finalize plans for what public health officials hope will be the biggest mass vaccination effort in the country's history.

Plans are currently set for clinics to take place in November. Those plans cannot be changed on a dime.

Dr. Perry Kendall, British Columbia's chief medical officer of health, said provinces and territories would need at least a week or two of notice to get clinics organized and staffed if the start date is going to change.

"If vaccine were available today, we'd still need time to train the delivery system for this specific vaccine, arrange clinics, advertise, review consent forms, pre-position vaccine supplies, ensure labelling and mixing (is) understood by all, etc.," Kendall said in an email.

Given that the first week of November is just three-and-a-half weeks away, unless word of a change comes soon there may be little gain from moving up the program start.

Meanwhile, Canadian TV sets tuned to U.S. TV channels are seeing images of Americans already being immunized against the virus.

The U.S. effort began Monday, with 2.4 million doses of a nasal spray vaccine expected to be shipped to states by the end of this week. That vaccine, FluMist, is not currently licensed in Canada. Injectable vaccine supplies will start to flow in the U.S. next week.

But where the U.S. is buying its pandemic vaccine from five suppliers, Canada has purchased its 50.4 million doses from a single producer, GlaxoSmithKline. The U.K.-based pharmaceutical giant has a flu vaccine production facility in Ste-Foy, Que.

GSK's European plant, based in Dresden, Germany, is already shipping vaccine. But it started making the pandemic product sooner than the Quebec facility, a senior GSK executive said in a media briefing on Monday.

Dr. Thomas Breuer explained the European production facility has two buildings and was able to start making pandemic vaccine in one while finishing its seasonal flu product in the other. The Quebec plant has only one building, so it had to finish the seasonal shots before starting on the pandemic product.

"It is currently envisioned that product will come out of the Canadian facility end of October, beginning November," said Breuer, a senior vice-president and chief medical officer for GSK.

But Dresden's quicker start will help speed vaccine approval here, Butler-Jones said.

Data generated by GSK in clinical trials in Europe will be used to approve the Canadian vaccine, he said. Health Canada will use those data to assess the safety and immunogenicity of the vaccine - in other words, its ability to induce a protective response.

"It's the same vaccine. It's not made in the same plant but all the processes and everything are the same," Butler-Jones said.

"So there's no need to wait for the Canadian confirmatory data which will come later. Because it's exactly the same process, the same vaccine from the same company."