A coronavirus vaccine developed by Britain’s University of Oxford and the pharmaceutical firm AstraZeneca has shown successful results in early trials. If it is approved by regulators, the vaccine appears suitable for a fast rollout around the globe. Early analysis of trials involving 20,000 volunteers in Britain and Brazil show the vaccine is at least 62% effective after two doses. In volunteers given a different dosing regimen — a half dose, followed by a full dose — that figure rose to 90%. The average efficacy of the two dosing methods is 70%. None of those given the vaccine developed severe COVID-19 illness. Andrew Pollard, director of the Oxford Vaccine Group, said the recent successful trials of three different vaccines by Oxford-AstraZeneca, Pfizer-BioNTech and Moderna, represent a...