AZ issues revised efficacy figures for COVID-19 shot

AstraZeneca has issued revised efficacy figures from the US trial of its COVID-19 vaccine following a complaint from independent monitors that figures from an interim analysis published earlier this week were out of date.

The new figures from AZ, which developed the vaccine in partnership with Oxford University, give an efficacy at preventing symptomatic COVID-19 of 76%, down from 79%, while the efficacy against severed or critical disease and hospitalisation remains at 100%

In patients aged over 65, the vaccine efficacy against symptomatic COVID-19 has been revised upwards by 5 percentage points to 85%.

AZ said that the figures presented on Monday were based on a pre-specified interim analysis with a data cut-off of 17 February.

The company immediately began working with the independent data safety monitoring board (IDSM) to provide the new analysis after its query earlier this week.

AZ pointed out that the primary analysis is pre-specified in the protocol and will form the basis of a filing with the FDA for an Emergency Use Authorisation.

This primary efficacy analysis included the accrual of 190 symptomatic cases of COVID-19 from the 32,449 trial participants, an additional 49 cases to the previously announced figures. Participants were randomised on a 2:1 ratio between the vaccine and placebo group.

No safety concerns were identified in the study and there was no evidence of thrombotic events, including the rare condition cerebral venous sinus thrombosis, in a safety review.

The new data emerged as EU leaders began talks about how to revive the bloc’s flagging vaccination programme.

Supply of the AZ vaccine to Europe has been a problem and there have been repeated threats from European officials to block exports to the UK, which got its order in three months before the EU.

UK prime minister Boris Johnson said on a Thursday call with journalists that Britain favours openness and did not want to see restrictions on exports to the continent.

Production of vaccines depends on several ingredients that are often manufactured in different countries, so blocking supplies could disrupt the entire system.

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