LONDON – A third COVID-19 vaccine has turned in positive results in the phase III interim analysis, with Astrazeneca plc/Oxford University reporting an average of 70.4% efficacy across two dose regimens for AZD-1222. Significantly, efficacy increased to 90% in the prime-boost arm of the trial, in which volunteers received half a dose, followed by a full dose. In addition to greater protection, that will make supplies go further.