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AstraZeneca vaccine trial data questioned by US agency

Tue 23 March 2021 10:27 | A A A

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(Sharecast News) - A US health agency has questioned AstraZeneca's efficacy data on its Covid-19 vaccine, with concerns raised that recently released results from clinical trials may include outdated information.

The long-awaited results from AstraZeneca's American trials were released on Monday. Involving 32,000 volunteers in the US, Chile and Peru, the trials showed the vaccine was 79% effective in stopping symptomatic Covid-19 and 100% effective in preventing people from falling seriously ill.

But on Tuesday, the US National Institute of Allergy and Infectious Diseases said the trial's Data and Safety Monitoring Board had notified it late on Monday that it was "concerned" by information released by AstraZeneca on initial data from the trial.

It said: "The DSMB expressed concern that AstraZeneca may have included outdated information from that trial, which may have provided an incomplete view of the efficacy data.

"We urge the company to work with the DSMB to review the efficacy data and ensure the most accurate, up-to-date efficacy data be made public as quickly as possible."

Fellow US regulator the Biomedical Advanced Research and Development Authority and AstraZeneca have also been notified by the DSMB. AstraZeneca has so far not commented.

Shares in AstraZeneca jumped on Monday following the release of the trial data as hopes rose that the drugmaker was moving closer to receiving emergency use authorisation in the US. By 1015 GMT on Tuesday, they had lost 1%.

The vaccine, which AstraZeneca has developed in conjunction with the University of Oxford, was approved by the UK regulator in December, and by the European Medicines Agency in January.

Its rollout on mainland Europe was temporarily halted earlier this month following concerns about rare side effects, including potential blood clots. But the EMA found no link between clotting and the vaccine, and nearly all countries have since resumed use.

Neil Wilson, chief market analyst at, called the statement by the NIAID "another headache" for the drugmaker.

"More doubts won't do the vaccine any favours," he said. "This will not do any favours for getting the shot into people's arms either: it's not just the rollout by government, it's people's willingness to get it. Europe sites on large stockpiles of the Astra vaccine, as countries cannot get the jab into arms."

The NIAID is part of the National Institutes of Health, America's medical research agency.

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