But its efficacy against the South African variant fell markedly when including mild and moderate cases, results showed.
In a Phase 3 trial in Britain that included 15,000 participants aged 18-84, including 27 percent over the age of 65, efficacy against mild, moderate and severe Covid was 96.4 percent against the original strain. In South Africa, a smaller Phase 2b trial of some 2,600 people found it was 48.6 percent effective, though the figure rose to 55.4 percent among HIV-negative volunteers.