OTTAWA -- Dr. Joss Reimer, medical lead for Manitoba鈥檚 Vaccine Implementation Task Force, says that new vaccine recommendations from the National Advisory Committee on Immunization on mixing mRNA vaccines will be a form of trial and error.
鈥淲ell in some ways, during a pandemic everything we do is a big human experiment,鈥� she said in an interview with CTV鈥檚 Question Period airing Sunday. 鈥淏ecause we're all having to learn together at the same time, about what works the best.鈥�
On Tuesday, NACI changed its guidelines to allow for Canadians to mix and match AstraZeneca with either mRNA vaccine from Moderna or Pfizer. There was no current data on the interchangeability of mRNA vaccines.
Chief Public Health Officer Dr. Theresa Tam says NACI still recommends sticking with the same mRNA vaccine regime for both doses, but that you can mix if there are problems with availability.
鈥淧eople who received the first dose of an mRNA vaccine, so that's Pfizer-BioNTech or Moderna vaccines, should be offered the same mRNA vaccine for the second dose,鈥� she said during a briefing on Tuesday.
NACI said in a statement there is no reason to believe that using a different mRNA vaccine for your second dose would result in any additional safety concerns.
Reimer says that mixing and matching vaccines is a not a new practice in the medical field.
鈥淲e have a lot of experience doing this in the past,鈥� said Reimer. 鈥淎nd what these small trials did is reassure us that it doesn't look like the COVID vaccines will be different than our previous experience.鈥�
There are currently two studies on mixing COVID-19 vaccines, both in Spain and the United Kingdom, whose preliminary results indicate that mixing and matching the AstraZeneca and Pfizer vaccines is safe.
