A federal advisory panel is recommending against mixing and matching COVID-19 vaccines.
In a statement released Friday (May 21), the National Advisory Committee on Immunization (NACI) recommended that “the vaccine series be completed with the same COVID-19 vaccine product when possible.”
Many Canadians had been awaiting the results of NACI’s recommendation after use of the AstraZeneca vaccine was stopped across many Canadian provinces, including B.C. and Ontario.
The panel said that if the vaccine used for the first dose isn’t available, then individuals should get their second dose using a similar vaccine – such as an mRNA vaccine if the person received one for their first dose.
“Currently, no data exist on the interchangeability of COVID-19 mRNA vaccines… at this time there is no reason to believe that mRNA vaccine series completion with a different authorized mRNA vaccine product would result in any additional safety issues or deficiency in protection,” NACI stated.
For those who received their first dose of AstraZeneca and either can’t, or don’t want to based on very low risks of blood clots, to receive their second dose of the same vaccine, NACI had limited advice. The panel said that the rate of Vaccine-Induced Immune Thrombotic Thrombocytopenia, or VIIT, is estimated to be between 1 per 26,000 and 1 per 100,000 persons for the first dose of AstraZeneca.
They recommended using the one-shot Johnson & Johnson vaccine, which has been approved by Health Canada but not actually used yet anywhere in the country. That vaccine, a viral vector one like AstraZeneca, has been linked to the same blood clots.
According to NACI, data only exists on the reactions that come from using AstraZeneca as dose one and Pfizer as dose two, but that further data should be incoming next month.