AstraZeneca Covid-19 Vaccine Trial Data Underscore Safety, Range of Efficacy

Peer-reviewed data from late-stage human trials of a Covid-19 vaccine developed by the University of Oxford and AstraZeneca PLC reaffirmed the shot’s strong safety results and provided some additional evidence that halving the first of two doses of the shot boosts its effectiveness. AstraZeneca and Oxford said the data gave them confidence to ask the U.K. and other countries for emergency-use authorization of the vaccine, but said regulators will have to decide which dosing regimen to approve. Last month, AstraZeneca and Oxford said trial data showed the vaccine was between 62% and 90% effective, but that the higher results were observed in a small subset of the wider trial.