Canada approves mixing and matching second vaccine doses, B.C. yet to confirm approval

For folks who got a first shot of the AstraZeneca vaccine and want to mix and match it with either Pfizer or Moderna for their second shot, Canada’s top doctor, Dr. Theresa Tam, confirmed Tuesday what provincial health officer Dr. Bonnie Henry has been hinting at for weeks.

"People who received a first dose of AstraZeneca Covishield vaccine may receive either AstraZeneca Covishield or an mRNA," said Tam.

The guidance originated from the National Advisory Committee on Immunization (NACI) and is based on data from ongoing studies in Europe. Tam advised that those who received Pfizer or Moderna for a first dose could get either shot for their second.

Dr. Brian Conway with the Vancouver Infectious Disease Centre hailed the news as very encouraging for getting life back to normal sooner rather than later.

"[It] makes the program more robust, it makes it more likely that we will achieve the goal of normal by Labour Day (Sept. 6)," said Conway Tuesday.

Nearly 275,000 British Columbians got an AstraZeneca vaccine as a first shot and have been waiting for guidance on their second.

Henry said Monday that those people would have a choice regarding which shot to get for their second dose, but that details wouldn't be released until Thursday. On Tuesday, after Tam’s announcement, B.C.'s Health Ministry still wouldn’t formally confirm the mixing and matching of vaccines for second shots in the province. But, the ministry issued a statement noting that the decision would be guided by science and NACI’s advice.

Ongoing studies from Spain and the U.K. indicate that there might be extra protection for those who do get AstraZeneca as a first dose and Pfizer as a second dose. The studies also suggest that there might also be more significant — but purely temporary — flu-like side effects associated with that mixing and matching.

Ismail Samudio works in the field of immunology and is the founder of Immunology Diagnostics. He confirmed that those are part of the findings from the research.

"My guess is people will find the more you mix and match the better immune responses you get," said Samudio, adding that "you may not feel so hot after the second."

With both AstraZeneca and the two mRNA vaccines now deemed safe to use as second doses by the country’s top doctor, immunologist Dr. Kelly McNagy advises that if you get a choice, you should take the first vaccine offered to you as a second dose.

"Whatever you can get as the soonest date, I would go with," said McNagy. "And with the mRNA vaccines, I think it’s likely that’s what they’ll be able to get and they can feel comfortable with that."

Logistics of timing for second shots of AstraZeneca, along with confirmation about mixing and matching in B.C., is expected Thursday.