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

Although it’s increasingly likely that one of the Covid-19 vaccines being tested will be approved or receive Emergency Use Authorization (EUA) before the end of 2020, experts are increasingly warning that widespread distribution may take a much longer time.