Advertisement Britain's Covid vaccine drive got another boost today as Johnson & Johnson confirmed that its world-first single shot jab blocks 66 per cent of coronavirus infections and prevents 100 per cent of hospital admissions and deaths among people who get it. Johnson and Johnson — the US drugs giant behind the jab — also found it prevented severe symptoms in 85 per cent of people and no-one who got the jab died or needed hospital treatment from 28 days after being inoculated. The 66 per cent efficacy was a global average, with the jab preventing 72 per cent of cases in the US but only 57 per cent in South Africa, which is being devastated by a mutated variant that appears to be less susceptible to vaccines and immunity from older versions of the virus. It is promising, however, that the jab still worked in South Africa and still prevented hospitalisation.