OTTAWA -- Prime Minister Justin Trudeau announced Friday that Pfizer-BioNTech has agreed to move up a portion of its vaccines scheduled for the summer, with an additional 1.5 million doses arriving in March.

This means Canada will have access to a total of eight million vaccine doses from Pfizer, Moderna, and AstraZeneca by the end of the first quarter, up from an original commitment of six million doses.

"With the newly confirmed delivery of an additional 1.5 million Pfizer-BioNTech vaccine doses arriving this month, as well as the 500,000 doses of the AstraZeneca Covishield vaccine that arrived this week from the Serum Institute, Canada is set to receive eight million doses of vaccines by the end of this quarter," said Procurement Minister Anita Anand, at a press conference on Friday.

Pfizer is also accelerating shipments for April and May by one million additional doses each month. By the end of the second quarter, Canada is on track to receive 36.5 million doses and by the end of the third quarter, 117.9 million, which will include the now-approved Johnson & Johnson vaccine.

Health Canada approved the one-dose candidate early Friday.

Asked whether the news of approvals and more doses arriving earlier advances the federal government鈥檚 longstanding end-of-September timeline to vaccinate all Canadians who wish to be vaccinated, the prime minister said Canada has "reasons to be optimistic. We鈥檙e going to be able to move things forward."

However, he added it鈥檚 possible disruptions to the vaccine supply chain may still occur.

Health Minister Patty Hajdu also weighed in on the possibility of a shortened vaccine timeline, echoing that while there are aspects of the procurement process Ottawa can control, other hurdles are out of the government鈥檚 hands.

"For example we have seen manufacturing delays and disruptions in the past," she said. "Things can happen internationally that are very challenging."

In mid-January, Pfizer announced it was retooling its Belgium plant to meet international demand of their vaccine, which meant Canada鈥檚 shipment was drastically reduced for several weeks. The European Commission鈥檚 announcement of new export control measures, also threatening to thwart international supply, came the same month.

For four weeks, deliveries, on average, were cut by 50 per cent. During the week of Jan. 25, the company did not ship a single vial of its vaccine to Canada. By Feb. 15, shipments began to ramp up again.

The Trudeau government is facing enhanced pressure to ramp up the speed of the rollout after U.S. President Joe Biden announced the country would be ready to vaccinate all adults by May. The U.K. is aiming to do the same by the end of July.

Canada鈥檚 Chief Public Health Officer Dr. Theresa Tam said on Friday the recent recommendation by the National Advisory Committee on Immunization to prolong the second dose of COVID-19 vaccines by up to four months is one way of ensuring more Canadians are at least partially protected, sooner.

"That is looked at as a public health strategy that maximizes the benefit of these vaccines," she said.