Vaccine advisers provide guidance on mixing AstraZeneca, mRNA vaccines

The National Advisory Committee on Immunization issued guidance today allowing for people who received the Oxford-AstraZeneca vaccine as their first dose to get an mRNA vaccine for their second.

A study in the United Kingdom reported last month that mixing AstraZeneca and Pfizer-BioNTech as first and second doses led to more reports of short-lived side-effects like fevers and fatigue but was otherwise safe.

The Spanish study concluded a second dose of Pfizer after a first dose of AstraZeneca produced more than twice the antibodies as a second dose of AstraZeneca.

All provinces paused the use of AstraZeneca for first doses in May as reports of vaccine-induced blood clots rose, but are anxiously waiting for the NACI advice on what to do with second doses.

Manitoba didn't wait for the advice, with health officials in that province announcing Monday they would start offering Pfizer-BioNTech or Moderna as a second dose to AstraZeneca recipients.

There are 41 confirmed or suspected cases of vaccine-induced blood clots following an AstraZeneca vaccination in Canada, including five deaths.