AstraZeneca is likely to run an additional global trial to assess the efficacy of its Covid-19 vaccine using a lower dosage, its chief executive was quoted as saying amid questions over the results of its late-stage study.

Instead of adding the trial to an ongoing US process, AstraZeneca might launch a fresh study to evaluate a lower dosage of its vaccine that performed better than a full dosage, Pascal Soriot told Bloomberg News.

“Now that we've found what looks like a better efficacy we have to validate this, so we need to do an additional study,” he said, adding that the new, likely global, study could be faster because it would need fewer subjects as the efficacy was already known to be high.