TORONTO - Canada's pandemic vaccine manufacturer says a single small dose of its vaccine was protective in a clinical trial conducted in Europe.

The GlaxoSmithKline vaccine contained an adjuvant, an additive that boosts the immune system's response to the vaccine.

The clinical trial tested the smallest dose yet of swine flu vaccine, showing that just about a third of the size of a standard dose would be protective.

The clinical trial tested a dose of 5.25 micrograms of vaccine with adjuvant, which GSK says is comparable to the 3.75 microgram dose the company expects to sell to Canada.

GSK says 98 per cent of subjects reached the threshold for protection with that dose when tested three weeks after the shot.

Last week Novartis, Sanofi Pasteur and CSL Limited announced that their vaccines were protective with a single dose.