A day after the National Advisory Committee on Immunization (NACI) said viral vector COVID-19 vaccines like those offered by AstraZeneca and Johnson & Johnson are not the “preferred” products, Prime Minister Justin Trudeau sought to reassure Canadians today that all vaccines approved for use in this country are safe and effective.

Speaking to reporters at a COVID-19 briefing today, Trudeau said Canadians should have no qualms about receiving a dose of the AstraZeneca product.

With Canada in the middle of a third pandemic wave, Trudeau said it is prudent for people to get the first shot offered to them to help drive down case counts and hospitalizations.

“Make sure you get your shot when it’s your turn. We are continuing to recommend to everyone to get vaccinated as quickly as possible so we can get through this,” Trudeau said.

“The impacts of catching COVID are far greater and far deadlier, as we’ve seen across the country, than potential side effects. Let me remind everyone that every vaccine administered in Canada is safe and effective, as evaluated by Health Canada.”

Trudeau and his wife, Sophie Grégoire Trudeau, each received a dose of the AstraZeneca product at an Ottawa pharmacy late last month. He said today he has no regrets.

NACI, an independent body composed of volunteer experts, said Monday that Canadians who are less likely to contract COVID-19 may want to wait until an mRNA shot from Pfizer or Moderna is available because those products don’t carry the same risk of very rare, but serious, blood clots.

“What we’ve said all along is that the mRNA vaccines are the preferred vaccine,” said Dr. Shelley Deeks, the vice-chair of NACI.

She said the suggestion that some people may want to wait for another shot comes after NACI received more information about the possibility of developing vaccine-induced thrombotic thrombocytopenia (VITT) — low platelet counts combined with blood clots.

Based on current data, NACI estimates VITT occurs at a rate of 1 in 100,000 shots rather than the 1 to 250,000 previously projected.

“The viral vector vaccines are very effective vaccines but there is a safety signal, a safety risk and the issue with the safety signal is that, although it’s very rare, it is very serious, so individuals need to have an informed choice,” Deeks said.

“When we first provided recommendations for COVID vaccines in Canada, we did not know about the vaccine safety signal. Now there’s been a vaccine safety signal and we modified the recommendations.”

WATCH: NACI says Pfizer and Moderna COVID vaccines are the preferred type

Dr. Shelley Deeks of NACI discussed with reporters the merits of receiving one type of COVID-19 vaccine over another. 2:32

Dr. Theresa Tam, Canada’s chief public health officer, said today she can “sympathize with people who find it difficult to follow the evolving advice” — given that public health officials have been saying for weeks that Canadians should opt for the first product offered to them.

She said Canadians should do a risk-benefit analysis before rolling up their sleeves for a shot.

In regions where COVID-19 is rampant, like Alberta and Ontario, it’s logical to go for the vaccine that’s available immediately, she said, because the risk of contracting the virus is high.

In places, like P.E.I., where transmission rates are lower, Canadians might want to wait for another option, she said. She added that Canadians should follow the guidance issued by local public health officials.

Tam said it’s not unusual for recommendations to change — especially at a time when rapidly developed vaccines are being deployed widely to beat down a pandemic that already has killed millions worldwide.

“NACI is taking the data that we’re gathering in real time into account and evolving advice based on that,” she said. “As benefits and risks are weighed, these parameters can shift over time.”

Tam said that while the current guidance is for AstraZeneca recipients to get a second dose of the same product, NACI is reviewing research on mixing AstraZeneca with an mRNA shot.

“There will be further advice forthcoming on that second dose based on the evolving science,” Tam said. “There will be further clarification and advice prior to individuals getting their second dose and we should watch that space.”

Public Services and Procurement Minister Anita Anand said Moderna is set to deliver one million doses of its product this week, days earlier than expected.

Pfizer is already on pace to deliver more than two million shots a week this month. That means more than three million mRNA shots will be fed into provincial immunization campaigns this week.

Moderna’s deliveries have been inconsistent since the onset of this vaccination effort. Deliveries have been slashed or delayed as Moderna — which did not have a track record before 2020 of producing anything at this scale — has struggled to ramp up production in the face of insatiable global demand.

Anand said there may be more certainty to these shipments moving forward as the company sorts through bottlenecks at its European facilities. “Moderna has been working with our department to solidify a more regular schedule,” she said.