WASHINGTON • AstraZeneca said that its Covid-19 vaccine was 76 per cent effective at preventing symptomatic illness and completely stopped severe or critical forms of the disease, citing a new analysis of up-to-date results for its major United States trial.

US health officials earlier in the week publicly rebuked the drug maker for using outdated information when calculating that the vaccine was 79 per cent effective.

The latest data was based on 190 cases among more than 32,400 participants in the US, 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," AstraZeneca BioPharmaceuticals R&D executive vice-president Mene Pangalos said in a statement yesterday.

AstraZeneca said it plans to seek US emergency use authorisation in the coming weeks and the latest data has been presented to the Data Safety Monitoring Board, an independent trial oversight committee.

AstraZeneca reiterated yesterday that the shot was 100 per cent effective against severe or critical forms of the disease. It also said the vaccine showed 85 per cent efficacy in adults 65 years and older.

The updated 76 per cent efficacy rate compares with rates of about 95 per cent for vaccines from Pfizer-BioNTech and Moderna.

Canada's health department said on Wednesday it has updated the product label for AstraZeneca's vaccine to warn of "very rare reports of blood clots associated with low levels of blood platelets".

REUTERS