The Scientific Committee Advising the Government of Canada on Vaccination today approved the possibility of changing the Covid vaccine between the first and second doses.
People who have taken a first dose of AstraZeneca can get either a second dose of the same medicine or a dose of an mRNA vaccine (Pfizer-BioNTech or Moderna), the National Vaccination Advisory Committee (CCNI) has announced.
Canadians receiving a first dose of messenger RNA vaccine should have the same preparation in their second dose, but if it is not available, they may be given another mRNA vaccine.
“The interchangeability of vaccines means that you can give a first dose of vaccine and safely make a different vaccine in your second dose to complete the series of vaccines needed to ensure optimal protection against Covid-19,” said Dr. Howard Dju, Deputy Head of Federal Public Health.
To make this recommendation, the National Vaccination Advisory Committee states that it has taken particular account of the risk of serious blood clots with the AstraZeneca vaccine.
He also says that such a mixture could lead to “the possibility of increased short-term side effects (…), mainly headaches, fatigue and a general feeling of malaise”.
The combination of vaccines from different manufacturers is not new: it has been applied against influenza or hepatitis A, the committee explains.
“I think we need to take a closer look at what will happen after this recommendation,” said Dr. Teresa Tam, head of public health, when asked about the risk of Canadians avoiding the AstraZeneca vaccine in the second dose.
“We do not want to leave vaccine doses unused,” he added. The decision to implement this recommendation is up to the Canadian provinces.
Several of them announced in May their decision to discontinue the AstraZeneca vaccine for citizens receiving the first dose of the vaccine due to the increase in the number of thrombosis associated with the vaccine.
However, it is still given to those who have taken a first dose of AstraZeneca and wish to take a second dose of the same medicine.
