Covid-19: AstraZeneca delivers but can't match rivals, here's what we know

The Astra-Oxford vaccine on average prevented 70% of cases in large trials in the U.K. and Brazil

The pressure was on AstraZeneca Plc and the University of Oxford after stunning Covid-19 vaccine trial results from Pfizer Inc. and Moderna Inc., and the U.K. partners delivered, even if they couldn’t match the data from the two front-runners.

Scientists will now closely scrutinize the preliminary results. The report is significant because Astra and Oxford are taking a different approach from the one used by Pfizer and Moderna, and vaccine advocates say multiple shots will be needed to stop a contagion that’s killed almost 1.4 million people. Here’s what we know, and what the results could mean in the battle.