A total of 4.8 million doses of the H1N1 vaccine will be delivered to the provinces by Sunday, up from about two millions doses shipped per week previously. (Ryan Remiorz /Canadian Press)

Ontario supplied hospitals with 200 additional ventilators on Friday in anticipation of a surge in swine flu cases.

In Toronto, three hospitals will house the new equipment, which is intended for patients who have serious cases of swine flu. St. Michael's Hospital, Sunnybrook and the University Health Network will store and share the ventilators with other hospitals in the Greater Toronto region that need them.

"What some hospitals have done in some regions has been very good," said Dr. Bernard Lawless, a critical care physician at St. Michael's, where he unwrapped a shipment of new ventilators. "With our surge capacity plan, I think the hospitals have built very good networks and collaboration amongst themselves.

"I am aware that there's been some situations where if there was a hospital in need another hospital or partnering hospital was able to help share resources."

Across the province, there are 85 serious cases of swine flu, which is caused by the H1N1 influenza A virus. Of those, 66 patients are on ventilators.

The new equipment is costing the province $7 million.

Two-thirds at risk of H1N1 infection

Meanwhile, blood test and survey results in Ontario suggest that two-thirds of the population is still at risk of contracting the H1N1 virus.

After the first wave of swine flu, health officials in Ontario launched a study aimed at getting an idea of what the second wave of the pandemic could look like.

About 900 people who were carefully selected to represent a cross-section of the population were recruited to give a blood sample and fill out an online questionnaire. The blood was tested in a lab for antibodies.

Researchers found that at the end of the first wave, between five to 11 per cent of the population had been infected with the H1N1 virus.

After taking into account the thousands of people who have been infected since the start of the second wave and the millions who have been vaccinated, two-thirds of the population is still at risk, public health officials said.

"What we are saying is that the majority of you out there, you are still susceptible to this," said Dr. Michael Gardam of the Ontario Agency for Health Protection and Promotion. "So, just because we have had two peaks, this doesn't mean that everybody has had it and we can all go home."

Health officials said the Ontario figures are a rough reflection of the entire country.

More vaccine doses to provinces

Across Canada, it's expected that a total of 4.8 million doses of the H1N1 vaccine will be delivered to the provinces by Sunday.

Until now, the largest shipment from supplier GlaxoSmithKline has been two million doses. The shipment will allow the provinces and territories to open up vaccination clinics to the general public, not just priority groups.

On Thursday, GlaxoSmithKline asked health officials to hold back a batch of swine flu vaccine that appears to be causing higher rates of severe allergic reactions.

The company said it's a precaution, pending an investigation. Manitoba health officials say they have noticed severe allergic reactions from the batch in question at a rate of one in 20,000, compared with the normal rate of one in 100,000.

Since most of the vaccine in question has already been used, the decision to withhold what's left is not expected to have an impact on overall supplies.