AstraZeneca has revised the efficacy rate for its US Covid-19 vaccine trial down to 76 per cent as the pharmaceutical group sought to address concerns that it had published incomplete interim data earlier this week. 

Mene Pangalos, AstraZeneca’s executive vice-president, said a reassessment showed the data were “consistent” with the previously reported numbers, which had an efficacy rate of 79 per cent. 

The disclosure followed a bruising few weeks for AstraZeneca, with the independent US data and safety monitoring board that oversaw its clinical trial objecting to the initial data release as potentially misleading. The Anglo-Swedish pharmaceutical group has also been locked in a bitter battle with the EU over accusations it has failed to meet supply targets.