LONDON—AstraZeneca PLC and the University of Oxford added their vaccine candidate to a growing list of shots showing promising effectiveness against Covid-19—setting in motion disparate regulatory and distribution tracks that executives and researchers hope will result in the start of widespread vaccinations by the end of the year.
AstraZeneca and Oxford said their vaccine was as much as 90% effective in preventing the infection without serious side effects in large clinical trials, though they said the vaccine’s efficacy…