A study says Ontario's H1N1 vaccination program averted nearly one million cases of influenza and as many as 50 deaths.

The study said Ontario could have seen an additional 420 hospitalizations, 28,000 visits to hospital emergency departments and 100,000 visits to doctors' offices if it hadn't offered the flu shot program.

The study was done by Beate Sanders, a health economist with the Ontario Agency of Health Protection and Promotion, and was published in the journal Vaccine.

Sanders said that while the $180-million vaccination program was expensive, it was cost-effective.

Sanders noted, though, that if the vaccine had arrived any later the program wouldn't have been as effective as it was. That's because Ontario started vaccinating just before the peak of the second wave of H1N1 infections, the study found.