The Canadian Press

A nurse draws a dose of H1N1 flu vaccine during the start of a clinical trial on the vaccine Monday, Aug. 31, 2009 at the University of Iowa Children's Hospital in Iowa City, Iowa. (THE CANADIAN PRESS/AP-Brian Ray, Pool)

TORONTO — A new study suggests an early and rapid rollout of swine flu vaccine could have a big impact on reducing the number of cases Canada sees this fall.

The scientific paper is what is called a modelling study, meaning the authors use statistical formulas to project what might happen if events played out according to a variety of projections.

The work, which is being published online by the Canadian Medical Association Journal, suggests that vaccine could have a disproportionately large effect on tamping down H1N1 activity, if it's used early.

The impact would be lessened, though, if the vaccine rollout comes later.

The Public Health Agency of Canada has been under pressure to speed up vaccination efforts, which are currently only due to start in the first week of November.

The study also suggests school closures would be effective at reducing transmission, but the authors note there are social costs to that kind of measure.