AstraZeneca Plc is to further evaluate the dosing for its candidate Covid-19 vaccine AZD1222 in light of interim data from trials in the UK and Brazil showing different efficacy rates for different dosing regimens. The data were disclosed on 23 November and showed vaccine efficacy of 90% when given as a half dose followed by a full dose at least one month apart. An efficacy rate of 62% was achieved when given as two full doses at least one month apart.
