U.K. trial explores scientific potential of more flexible vaccine rollouts

CBC News · Posted: Mar 26, 2021 

A woman gives the thumbs up after receiving her first dose of Pfizer-BioNTech’s COVID-19 vaccine at a mass vaccination clinic in Toronto’s east end run by the Scarborough Health Network last week. (Evan Mitsui/CBC)
We’re answering your questions about the pandemic. Send yours to COVID@cbc.ca, and we’ll answer as many as we can. We publish a selection of answers online and also put some questions to the experts during The National and on CBC News Network. So far, we’ve received more than 72,000 emails from all corners of the country.

Does your second dose of COVID-19 vaccine have to be the same brand as your first?

Health officials don’t recommend having different types of COVID-19 vaccines for your two shots, but doctors say a unique clinical trial in the United Kingdom could inform a more flexible rollout in Canada.

People like Joseph Frisina of Montreal are asking CBC News about the pluses and minuses of receiving a first dose of one vaccine and a different brand for the second shot.

Frisina said he received his first dose of the AstraZeneca-Oxford vaccine in Quebec and plans to be in the U.S. when time comes for his second, where he’ll likely be offered Pfizer-BioNTech. He wants to know if it could be risky.

Dr. Lisa Barrett, an infectious diseases physician and researcher at Dalhousie University in Halifax, said she doesn’t see any reason to be worried about safety.

Barrett likens the first shot of the two-dose coronavirus vaccines to giving your immune system an elementary school education. The second dose broadens the response to a university level.

“What your first shot does is it sends up a battle cry, if you will, to your immune system to rally those specific troops together to get an immune response that’s good to this particular part of COVID vaccine and then it adds some memory,” Barrett said.

“The quality of the immune response after one shot is generally OK, but still not highly sophisticated.”

That’s why federal, provincial and territorial health officials all recommend that people be fully immunized to protect against COVID-19.

To read more, click on https://www.cbc.ca/news/health/covid-19-vaccine-mix-match-1.5964162