AstraZeneca says COVID-19 vaccine shows 76% efficacy in updated analysis of U.S. trial

AstraZenecasaid its COVID-19 vaccine had a76 per cent efficacy rateat preventing symptomatic illness in a new analysis of its major U.S. trial slightly lower than the level announced earlier this week in a report that was criticized for using outdated information.

U.S. health officials had publicly rebuked the drugmaker for not using the most up-to-date information when it published an interim analysis on Monday that said the vaccine had a 79 per cent efficacy rate.

The latest data was based on 190 infections among more than 32,400 participants in the United States, Chile and Peru. The earlier interim data was based on 141 infections through Feb. 17.

"The primary analysis is consistent with our previously released interim analysis, and confirms that our COVID-19 vaccine is highly effective in adults," Mene Pangalos, executive vice president of BioPharmaceuticals R&D atAstraZeneca,said in a statement.

AstraZenecasaid it plans to seek U.S. emergency use authorization in the coming weeks and the latest data has been presented to the independent trial oversight committee, the Data Safety Monitoring Board.

AstraZenecareiterated on Thursday that the shot, developed with Oxford University, was 100 per centeffective against severe or critical forms of the disease. It also said the vaccine showed 85 per centefficacy in adults 65 years and older.

WATCH | Fauci says AstraZeneca vaccine is safe and effective:

AstraZeneca vaccine trial in U.S. shows it's safe, effective, Fauci says

3 years ago

Duration 1:05

Top U.S. infectious disease expert Dr. Anthony Fauci says interim data shows that the AstraZeneca-Oxford COVID-19 vaccine is 78.9 per cent effective overall.

"A lot of us were waiting for this large, well-constructed and reported Phase III study," said Paul Griffin, a professor at the University of Queensland.

Although AstraZeneca's vaccine has been authorized for use in more than 50 countries, including Canada, it has not yet been given the green light in the U.S.

Easier and cheaper to transport

"This appears to be a very effective vaccine with no safety concerns. Hopefully, this should now give people the confidence that this vaccine is the right one to continue to use moving forward," Griffinsaid, noting that he and his parents have taken the vaccine.

The updated 76 per centefficacy rate compares with rates of about 95 per centfor vaccines from Pfizer-BioNTech and Moderna.

TheAstraZenecavaccine is, however, seen as crucial in tackling the spread of COVID-19 across the globe, not just due to limited vaccine supply but also because it is easier and cheaper to transport than rival shots. It has been granted conditional marketing or emergency use authorization in more than 70 countries.

The highly unusual rebuke from U.S. health authorities had marked a fresh setback for the vaccine that was once hailed as a milestone in the fight against the COVID-19 pandemic, but has been dogged by questions over its effectiveness and possible side effects.

The shot has faced questions since late last year when the drugmaker and Oxford University published data from an earlier trial with two different efficacy readings as a result of a dosing error.

Then this month, more than a dozen countries temporarily suspended giving out the vaccine after reports linked it to a rare blood clotting disorder in a very small number of people.

The European Union's drug regulator said last week the vaccine was clearly safe, but Europeans remain skeptical about its safety.

Countries including Germany, France, Italy and Spainsaid they would use the vaccine after the update from the European Medicines Agency, but the Danish governmenthas decided to keep its suspension of the AstraZeneca vaccines for three more weeks.

Denmark paused the use of the AstraZenecashot as a precautionary measure on March 11, after reports that a 60-year-old woman died with blood clots in several parts of her body a week after she received the vaccine. News that asecond person in Denmark had died after getting the AstraZeneca vaccine was also reported.

Danish health authorities saidthey have no evidence the vaccine was responsible for either death. Norway and Sweden also have paused the use of the AstraZeneca vaccine.

Health Canada said this week it'supdating the label on the AstraZeneca-Oxford and CovishieldCOVID-19 vaccinesto add information about "very rare reports of blood clots associated with low levels of blood platelets," but says the shot remains safe and that the benefits of getting the vaccineoutweigh the risks.