OTTAWA -- Prime Minister Justin Trudeau says he's been assured that COVID-19 vaccination deliveries will accelerate in coming weeks, and that includes four million doses of the Pfizer-BioNTech vaccine by the end of March.

He says the pharmaceutical giant has confirmed it will deliver the doses they promised last November, and that Canada has also ordered four million additional doses of the Moderna vaccine, which will arrive over the summer.

Trudeau outlined several measures to rein in the pandemic, including the start of strict travel requirements Feb. 22 and a $53-million investment on a strategy to monitor more infectious variants like the ones first detected in the U.K. and South Africa.

"Nobody wants a third wave to start, particularly not one comprised of new, more communicable variants that can cause real challenges," Trudeau said Friday from Rideau Cottage.

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

Trudeau's updated delivery schedule from Pfizer also includes 10.8 million doses to be delivered between April and June, and all remaining doses -- 40 million in total -- arriving by the end of September.

Production delays have been blamed for a lull in Canada's vaccination efforts since mid-January, when Pfizer slowed production at its plant in Belgium.

Trudeau said he can say with confidence that all Canadians who want a dose will still be able to get one by September.

The assurance came as Canada's top doctors said COVID-19 infections appear to be on a downward trend but that the worrisome variants were posing an increasing threat to containing the pandemic.

Chief Public Health Officer Theresa Tam said earlier Friday that aggressive vaccinations will play a key part in addressing COVID-19 spread but that is just one suppression tool as modelling data in the nation's hot spots point to a likely third wave.

Tam said at least three provinces are reporting evidence of community spread of the new variants.

"We've made great progress, and are now almost two thirds of the way down this curve," said Tam, adding that ongoing vigilance was vital.

"Look at the European countries -- they give us a clue as to what might happen if variants are circulating, and we let our guard down. That massive acceleration into that third resurgence, if you like ... will happen really fast."

There are more than 429 cases of the variant first identified in the U.K., and 28 cases of the variant first identified in South Africa reported across eight provinces, she said.

So far, there has only been one report of the variant first found in Brazil.

A key part in the battle against the new variants are the federal government's strict new quarantine and testing measures for travellers arriving in Canada.

In announcing the new rules Friday, Trudeau reiterated pleas that non-essential travel stop due to the threat of a possible third wave in infections.

Trudeau says new requirements that demand a COVID-19 test for new arrivals and a three-day quarantine while awaiting results are not meant to be punitive but to help stop the spread of COVID-19.

According to federal data, as of Thursday there have been 817,163 cases of COVID-19 in Canada, with 37,747 of them considered active cases.

Tam urged Canadians to refrain from gathering just as much of the country entered a long weekend that included Family Day in several provinces, and Valentine's Day.

The Ontario Medical Association said Friday it's more important than ever to limit physical interactions, suggesting phone calls or virtual meals with friends and relatives.

"COVID-19 has challenged us all to find meaningful ways to connect from a distance," president Dr. Samantha Hill said in a release.

"For the sake of all of our families, this Family Day cherish, support and connect with your family while adhering to public health guidelines."

The warnings come as Ontario reported 1,076 new cases of COVID-19 and 18 more deaths linked to the virus.

Health Minister Christine Elliott said that included 361 new cases in Toronto, 210 in Peel Region, and 122 in York Region.

Meanwhile, Quebec reported 984 new COVID-19 cases and 25 more deaths, including four in the previous 24 hours.