During a pandemic, hospitals may need to make room for a surge in patients.

The U.S. government will foot the bill for vaccinations against swine flu that will probably begin in mid-October, a federal health official said Thursday.

A final decision has not been made, but plans are on track to offer a vaccine in the fall, assuming safety and effectiveness tests go well, Health and Human Services Secretary Kathleen Sebelius told a summit of 500 state and local leaders at the National Institutes of Health.

School-age children, young adults with conditions such as asthma, pregnant women and health workers are likely to be first in line, Sebelius said.

"We have already appropriated about a billion dollars to buy the bulk ingredients," Sebelius told the summit.

Delegates at the day-long meeting are discussing lessons learned during the spring and summer wave of H1N1 illnesses, and how to prepare for the possibility of a more severe outbreak in the fall.

U.S. President Barack Obama telephoned the meeting from Italy, asking officials to make sure "we are promoting vigilance and preparation" rather than panic.

In the U.S., 50 outbreaks have been documented at summer camps so far.

On Thursday, medical experts gathered for the Canadian Pandemic Preparedness Meeting in Toronto to discuss their strategies for dealing with a worst-case scenario of a second, more serious wave of swine flu in the fall.

They assessed what research needs to be done to better understand the virus, and how hospitals could prepare to make room for people with severe respiratory failure, said Dr. Donald Low, microbiologist-in-chief at Toronto's Mount Sinai Hospital, who attended the meeting.

"What I mean by that is, people who are going to have to go into the intensive care unit, are going to have to go on ventilators, are going to have to be supported for anywhere from a week to two weeks," Low said Thursday.

"And having the capacity to be able to manage those patients considering the experience in Winnipeg, where they [were] just about at the brink, where they weren't going to be able to handle any more cases if they came in the front door."

Last month, Dr. David Butler-Jones, Canada's chief public health officer, said preliminary work on a vaccine against H1N1 is underway. Canadian health officials are also thinking about whether a swine flu vaccine should be offered to everyone, and who should receive priority.

Seasonal flu shots will also be offered.

As of Thursday, the Public Health Agency of Canada said a total of 9,429 laboratory-confirmed cases of pandemic (H1N1) 2009 have been reported, including 878 hospitalizations and 37 deaths.

With files from The Associated Press