Ever-changing recommendations on vaccines can be confusing, but these must evolve as the scientific research on vaccine evolves: Dr. Tam

Chief Public Health Officer Dr. Theresa Tam says the National Advisory Committee on Immunization is giving the measure the green light for people who received the Oxford-AstraZeneca vaccine as their first dose.

Dr. Theresa Tam acknowledges that the ever-changing recommendations on vaccines can be confusing to Canadians.

But she says those recommendations must evolve as the scientific research on vaccines evolves.

Dr. Tam says the new recommendation doesn't mean Canadians who received the AstraZeneca shot need to switch brands for their second dose.

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.

All provinces paused the use of AstraZeneca for first doses in May as reports of vaccine-induced blood clots rose.