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Canada to study mixing-and-matching of COVID-19 vaccines

NEWS STAFF | posted Thursday, May 20th, 2021

A new Canadian study is set to begin, looking at the effects of “mixing-and-matching” COVID-19 vaccines in adults.

The COVID-19 Immunity Task Force and the Vaccine Surveillance Reference Group will assess the safety and effectiveness of using two different COVID-19 vaccines for the first and second dose, as well as the effects of increasing the interval between doses.

There are currently four COVID-19 vaccines approved for use in Canada — Pfizer-BioNtech, Moderna, AstraZenca and Johnson & Johnson.

Several provinces have temporarily suspended the use of the AstraZenca vaccine due to rare blood clots in some recipients. That has heightened the interest in whether or not it could be possible to administer a different vaccine to those people as a second shot.

Preliminary results of an ongoing study in the United Kingdom suggest alternating the AstraZeneca and Pfizer vaccines causes more frequent mild to moderate symptoms, but there are no other safety concerns from mixing those vaccines.

“Studies on mixed COVID-19 vaccine schedules are underway in other countries, including the United Kingdom,” says Dr. Theresa Tam, Canada’s Chief Public Health Officer. “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.”

Up to 1,300 participants will be enrolled in the trials which is set to take place using the Canadian Immunization Research Network’s Clinical Trials Network in Nova Scotia, Quebec, Ontario, Manitoba, Alberta and British Columbia. Anyone who is 18 years of age or older and in good health is eligible to participate in the study.


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