‘We need to know with reasonable certainty,’ doctor says about mixing vaccines

While the Saskatchewan government has signalled it intends to use doses of Pfizer’s COVID-19 vaccine to administer second shots for those who first received AstraZeneca, an infectious disease physician in Regina prefers to wait for results of a study on mixing vaccines.

Right now, researchers in the United Kingdom are studying the practice and the results are expected in the near future.

Dr. Alex Wong wants to see that data first before proceeding.

“The guidance is still kind of yet to be determined because we need to actually know with reasonable certainty that giving a second dose of mRNA — specifically Pfizer if you’ve had a first dose of AstraZeneca — is safe and as effective as getting a second dose of AstraZeneca,” Wong said.

On Wednesday’s Greg Morgan Morning Show, Wong said there are many “moving parts” that are pushing governments toward the practice.

The risk of rare blood clots has been well-documented and vaccination campaigns are now reaching younger populations, while the country’s advisory committee on vaccines is recommending AstraZeneca be used only for Canadians 30 and older.

At the same time, Wong says Alberta and Manitoba remain hard hit by the virus. As well, further shipments of the AstraZeneca vaccine are uncertain.

“So all of these risk-benefit pieces are changing,” Wong said.

In Saskatchewan, active cases have dropped to 2,064, the lowest point since April 2. The seven-day average of new cases is 204, or 16.6 per 100,000 people. However, Wong said other metrics remain troubling.

Test positivity rates, he said, “across the province right now are still quite high.” Now that the weather permits, he urged people to do their socializing in a safe manner outside.

“If we’re not careful, it could take a lot longer to get to where we want to in terms of having our curve very, very flat. So we need to maintain that diligence,” Wong said.