Prime Minister Justin Trudeau joined Canada's top doctors in warning that more infectious COVID-19 variants threaten to spark a third wave, even as he announced Canada would receive millions more vaccine doses than previously expected.

Trudeau urged the public to refrain from unnecessary travel and gatherings as the long weekend approached, noting a fast-tracked shipment of millions of COVID-19 vaccines in coming months will not be enough to combat worrisome variants that have overtaken other countries.

"Nobody wants a third wave to start, particularly not one comprised of new, more communicable variants that can cause real challenges," Trudeau said while announcing $53 million dedicated to clamping down on these cases.

"You might be worried about these new strains, well we're putting our best experts on it, researchers, epidemiologists, modelers."

COVID-19 infections appear to be on a downward trend: Dr. Theresa Tam

Chief Public Health Officer Theresa Tam says COVID-19 infections appear to be on a downward trend.

But she's concerned variants are posing an increasing threat to containing the pandemic.

That's because at least three provinces are reporting evidence of community spread of these more contagious variants.

Dr. Tam says ongoing vigilance is vital if we want to avoid a massive acceleration of cases into a third wave as seen in some European countries.