AstraZeneca revises down efficacy rate on US Covid vaccine trial

by | Mar 25, 2021

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Pharma giant AstraZeneca revised down the efficacy rate for its US Covid-19 vaccine trial to 76% after authorities there said the company had published incomplete data in trial results.
The company earlier this week said the drug had an efficacy rate of 79%. AstraZeneca executive vice-president Mene Pangalos said the reassessment showed the data were “consistent” with the previous figures.

“In addition, results were comparable across age groups, with vaccine efficacy of 85% in adults 65 years and older. A key secondary endpoint, preventing severe or critical disease and hospitalisation, demonstrated 100% efficacy,” the company said on Thursday.

There were eight cases of severe Covid-19 observed in the primary analysis with all of those cases in the placebo group, it added.


The National Institute for Allergy and Infectious Diseases had written to the company saying it was concerned that interim data, with a cut-off date of mid-February, would show a more positive efficacy rate, writing that it thought the actual rate could be between 69% – 74%.

“We look forward to filing our regulatory submission for emergency use authorisation in the US and preparing for the rollout of millions of doses across America,” Pangalos said.

The US trial included more than 32,449 participants, with two-thirds taking the vaccine and the rest a placebo. It resulted in 190 cases of Covid-19, according to the new analysis, up 49 from initial analysis.


“There are 14 additional possible or probable cases to be adjudicated so the total number of cases and the point estimate may fluctuate slightly,” AstraZeneca said.

Criticism from the US has further tarnished the company’s image in recent days. It is currently embroiled in a row with the European Union and UK over the supply of vaccines to the 27-nation bloc.

The EU is threatening an export block unless the company meets supply level promises.


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