Editors’ note: This is a developing story. Find most recent coverage here.
Written by: Jaymee Salisi, News Writer
On June 1, 2021, the Public Health Agency of Canada updated their guidelines regarding the use of two different authorized COVID-19 vaccines for each dose.
A COVID-19 mRNA vaccine triggers an immune response, which produces proteins to protect the body from COVID-19. Pfizer and Moderna vaccines may be used interchangeably, as they are both mRNA vaccines.
The National Advisory Committee on Immunization (NACI) updated their guidelines following an “increasing availability of mRNA vaccines in Canada.” NACI said an mRNA vaccine is the preferred first dose followed by an AstraZeneca dose, as there is evidence of the technology providing a more effective immune response.
The information about switching between COVID-19 vaccines comes from the preliminary results of a Spanish study suggesting an increase in effectiveness when two different doses are combined.
Research found the mixed doses “jolt the immune system into producing many more antibodies.” This means more protective proteins are produced by the immune system to remove the COVID-19 virus from the body.
“Receiving a second vaccine dose for a two-dose schedule is essential to provide better and longer-term protection against COVID-19 for individuals and for the entire community,” according to NACI.
Canada’s Chief Public Health Officer Dr. Theresa Tam advised people to use the same mRNA vaccine for both doses if it is accessible. However, the similarities in mRNA technology between the Pfizer and Moderna vaccines allow for the two to be safely mixed and matched.
Approved for people 18 years or older, AstraZeneca/COVISHIELD vaccines use a harmless virus — similar to the common cold — to build an immune response against the virus that causes COVID-19.
Dr. Tam said switching between vaccine brands has been applied to different types of vaccines in the past, such as influenza and hepatitis A.
Although BC community clinics will be stocked with both mRNA vaccines, they may run out of Pfizer supply. For those who received Pfizer as their first dose, they may be offered Moderna as their second.
“If you are offered the other mRNA vaccine, please be assured that it is safe and it is effective to have either one of these products here in Canada and here in BC. They are both highly effective and very safe. Really, these are the same vaccines,” Provincial Health Officer Bonnie Henry said.
More information about COVID-19 vaccines can be found on the website for the government of Canada.
