How effective is the AstraZeneca vaccine? What you need to know

Health Canada has approved its third COVID-19 vaccine, authorizing the jab made by AstraZeneca and Oxford University after a lengthy review of clinical trial details.

Here’s what we know about the AstraZeneca product:

Why did it take so long to approve?

Health Canada’s regulatory team had been reviewing AstraZeneca’s application since Oct. 1, 2020, and was undergoing its final assessment of clinical data as of late last month.

Dr. Supriya Sharma, Health Canada’s chief medical adviser, said in January the review was “a bit more complicated’’ because some volunteers in AstraZeneca’s trials only received a half dose at first.

How effective was the vaccine in clinical trials?

Data released by the company suggested the vaccine was 62 per cent effective in clinical trials when two full doses were distributed a month apart. Another dosing regimen, where a half dose was followed by a full dose 28 days later, was shown in interim data to be 90 per cent effective.

Sharma says the recommendations are to administer two shots with the same dosage amount four to 12 weeks apart.

AstraZeneca’s efficacy compares with the 95 per cent efficacy from the clinical trials of PfizerBioNTech and Moderna.

Does it work against the new variants?

A group of experts on immunization working with the World Health Organization is recommending the use of AstraZeneca’s vaccine, even in countries where variants emerged as dominant.