AstraZeneca COVID-19 vaccine protective against severe outcomes from delta variant, more data suggests

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Doctor: Mask mandates send 'wrong signal,' undermines confidence in vaccines

Dr. Jay Bhattacharya tells 'America's Newsroom' the coronavirus vaccine is extremely effective and the return of mask mandates would undermine confidence in getting it.

Early findings from the real-world vaccine rollout in Canada suggested one dose of Oxford-AstraZeneca's COVID-19 shot, not yet authorized in the U.S., was protective against poor outcomes from the highly transmissible delta variant.

Researchers affiliated with University of Toronto recently posted results in medRxiv ahead of peer review, analyzing nearly 70,000 individuals in Ontario aged over 16 and infected with COVID-19 from December to May, with a variant of concern behind 9.7% of cases.

Results indicated just one dose of the AstraZeneca vaccine was 88% effective against severe outcomes from the delta variant, compared to 78% protection afforded by a single dose of the Pfizer vaccine and 96% from a single dose of the Moderna vaccine. The study couldn’t estimate vaccine effectiveness against delta after a full series of AstraZeneca or Moderna vaccine "due to zero vaccinated testpositive cases."

 July 7, 2021: A health worker prepares to administer a jab of the AstraZeneca COVID-19 vaccine during a vaccination drive for people ages 30 to 39 in Mexico City. ( (AP Photo/Marco Ugarte))

The delta variant has been detected in at least 124 countries, according to the World Health Organization.

ASTRAZENECA, PFIZER COVID-19 VACCINES EFFECTIVE AGAINST DELTA VARIANT, STUDY FINDS

"Our real-world vaccine effectiveness estimates suggest that even a single dose of these 3 COVID-19 vaccine products provide considerable protection against symptomatic infection and severe outcomes caused by these 4 currently circulating VOCs [variants of concern], and that 2 doses are likely to provide even higher protection," study authors wrote. "Our findings have public health policy implications worldwide."

Researchers suggested areas with limited vaccine supply could delay the second dose to blanket vaccine wider across the population to first-time recipients. 

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AstraZeneca lauded the results in a company statement released Friday, with BioPharmaceuticals R&D Executive Vice President Mene Pangalos writing, "With different variants threatening to disrupt our route out of the pandemic, this real-world evidence shows that Vaxzevria, along with other vaccines used in Canada, provides a high level of protection against the most serious forms of the disease, even after just one shot. It is essential that we continue to protect as many people as possible in all corners of the world in order to get ahead of this deadly virus."