TORONTO — Canada’s National Advisory Committee on Immunization says people who got the Oxford-AstraZeneca vaccine for the first dose can be offered either Pfizer-BioNTech or Moderna for the second.

The advice affects more than two million Canadians who received the Oxford-AstraZeneca vaccine before provinces stopped using it for first doses last month. The vaccine is potentially linked to a rare but serious blood clotting syndrome. In Canada, 41 confirmed or suspected cases of vaccine-induced thrombotic thrombocytopenia have been diagnosed and five people have died.

Several European countries are giving Pfizer or Moderna as second doses to AstraZeneca recipients, including Denmark, Finland, France, Germany, Sweden, Norway and Spain.

NACI’s published report says AstraZeneca recipients can be offered the same vaccine if they want it, or can be given either Pfizer or Moderna. They say they are basing their advice on the risk of VITT, and emerging evidence that mixing and matching different types of vaccines is not only safe but may produce a better immune response.

The guidance is not binding but most provincial governments have indicated they were waiting for the information before setting their policies for second doses.