Fortune or foresight? AstraZeneca and Oxford's stories clash on COVID-19 vaccine

The discrepancy, reported for the first time by Reuters, centres on the regimen administered to a smaller group of volunteers in the late-stage trials, of half a dose followed by a full dose. This diverged from the original plan of two full doses, given to the majority of participants. The half-dose pattern was found to be 90% effective, versus the 62% success rate of the two-full-dose main study, based on interim data. AstraZeneca’s research chief told Reuters 10 days ago, when interim trial data was released, the half-dose was given inadvertently as a first shot to some trial participants, and emerged as a stroke of fortune - “serendipity” - that scientists expertly harnessed.