“It’s not about trying to supersede AstraZeneca, it’s really looking about the different combinations,” says co-principal investigator Dr. Manish Sadarangani.
B.C. is looking for 300 volunteers to be part of a national study into the impact of changing COVID-19 vaccine dose intervals and whether it’s safe to mix vaccines.
Dr. Manish Sadarangani, a Vancouver-based principal investigator on the project, said the study would determine the effect of different COVID-19 dosing intervals on immunity, and what the immune response is if two doses of different COVID-19 vaccines are used.
When the Pfizer and Moderna vaccines were rolled out in B.C. last December and January the set dose interval was between 14 and 21 days.
However, manufacturing and supply problems meant vaccines dried up in late January and early February, forcing the provincial health officer, Dr. Bonnie Henry, to extend the interval between first and second dose to four months. This gap is now approved by Canada’s National Advisory Committee on Immunization.
Reports of blood clots in B.C. from the AstraZeneca vaccine have also led to concerns from people who are set to receive the second dose of that vaccine. A report from Spain released Tuesday found that giving a second dose of Pfizer to someone who had received a first shot of AstraZeneca was safe and effective.
Sadarangani said this study would not focus on any particular vaccine.
“If you have a dose of the Moderna vaccine first, or the Pfizer vaccine first, or the AstraZeneca vaccine first, (we ask) what is the difference if you have a different vaccine or the same vaccine as your second dose?,” he said.
“It’s not about trying to supersede AstraZeneca, it’s really looking about the different combinations.
“The bottom line is that during the pandemic, we’ve had supply issues with one or other of the vaccines and it’s possible that will continue.”
Sadarangani said the research deadline for the federally funded project was “as soon as possible”.
He said B.C.’s 300 volunteers would be randomly assigned to a study group and provide blood samples four times over the course of a year.
“Depending on what you have for your first dose, or if you haven’t had a vaccine, you will get allocated into one of the 13 study groups,” he said.
In a statement, Dr. Theresa Tam, Canada’s chief public health officer, said studies on mixed COVID-19 vaccine schedules were underway in the U.K.
“In addition to international data, this Canadian study will help inform Canada’s public health recommendations on the potential to use different combinations of vaccines for the first and second dose, as well as different dosing intervals,” Tam said.
B.C. has 4,815 active cases of COVID-19, of which 340 are being treated in hospital including 118 in intensive care. The were 521 new cases reported on Wednesday and eight deaths.
There have been over 2.6 million doses of vaccine administered in B.C., of which 135,246 are second doses.
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