An additional, global trial of the Oxford COVID-19 vaccine will be conducted to quell doubts over the 90% efficacy interim finding reported in phase three trial results earlier this week, AstraZeneca says.

The company’s CEO, Pascal Soriot, says a new study will evaluate whether a half-dose regimen, which was mistakenly given to more than 2700 trial participants, outperforms two full doses of the vaccine across all ages and ethnicities.

“Now that we’ve found what looks like a better efficacy, we have to validate this, so we need to do an additional study,” Mr Soriot told US news outlet Bloomberg.

He said this would likely occur through a standalone study rather than adding an arm to ongoing studies but added that he didn’t expect any delay to regulatory approval processes in the UK or Europe.