VANCOUVER — British Columbia is not changing its approach to administering second doses of AstraZeneca vaccine in light of updated recommendations from Canada’s immunization advisory committee, health officials said Thursday.
The latest national guidance recommends those who received the viral vector vaccine for their first dose get an mRNA vaccine for their second, citing growing evidence that a mix-and-match approach for AstraZeneca recipients provides superior protection.
Despite those findings, provincial health officer Dr. Bonnie Henry said the B.C. government remains confident that two doses of viral vector vaccine adequately protect against COVID-19.
“Here in B.C., our advice has not changed,” Henry said. “We can be very reassured that two doses of whatever vaccine you receive are safe and effective.”
Henry’s response echoed the message coming from the National Advisory Committee on Immunization earlier in the day, which said Canadians who have already received two doses of AstraZeneca can “rest assured” that they are well protected.
B.C. health officials pointed to the “real-world” evidence gathered locally as well as in the U.K., where two doses of AstraZeneca were recently found to be 85 to 90 per cent effective against symptomatic COVID-19.
Henry also noted the data suggesting there’s increased effectiveness associated with mixing vaccines remains preliminary.
“It’s important to remember that this is new information, that we are continuing to learn as we use more of these vaccines around the world and as more studies are done,” the provincial health officer said.
“Mixing an mRNA after a dose of AstraZeneca may give some boost to the immune system, but we don’t know whether that translates into (being) better protected or not. We don’t know that definitively, and we may not know that for some time.”
British Columbia’s approach remains that people who received the AstraZeneca vaccine are free to choose whether they want another viral vector dose or would prefer a shot of Pfizer-BioNTech or Moderna.
NACI’s guidance recommends that people who received an mRNA vaccine first get another for their booster, but that either of the two will do.
What’s important is for the public to get fully protected by receiving a second dose, Henry said, and she encouraged people to do so “as soon as it is available to you.”
While announcing their updated recommendations Thursday, NACI officials also cited the very rare risk of blood clots associated with the AstraZeneca vaccine. As of May 31, three people in B.C. had developed vaccine-induced immune thrombotic thrombocytopenic, or VITT.
According to the B.C. Centre for Disease Control, the risk of serious blood clots after receiving a first shot of AstraZeneca is about one in 100,000. That risk is said to decrease to one in 600,000 for second doses.
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