AstraZeneca Covid-19 vaccine shows 74% efficacy in large US trial

CHICAGO AstraZeneca's Covid-19 vaccine demonstrated 74 per cent efficacy at preventing symptomatic disease, a figure that increased to 83.5 per cent in people aged 65 and older, according to long-awaited results of the company's United States clinical trial published on Wednesday.

Overall efficacy of 74 per cent was lower than the interim 79 per cent figure reported by the British drugmaker in March, a result AstraZeneca revised days later to 76 per cent after a rare public rebuke from health officials that the figure was based on "outdated information".

The data looked at more than 26,000 volunteers in the US, Chile and Peru, who received two doses of the vaccine spaced about a month apart. The results were published in the New England Journal of Medicine.

There were no cases of severe or critical symptomatic Covid-19 among the more than 17,600 participants who got the vaccine, compared with eight such cases among the 8,500 volunteers who got the placebo.

There were also two deaths in the placebo group but none among the vaccinated.

"I was pleasantly surprised," Dr Anna Durbin, a vaccine researcher at Johns Hopkins University and one of the study's investigators, said of the overall result. "It was also highly protective against severe disease and hospitalisation."

There were no cases of a rare but serious blood clotting side effect called thrombosis with thrombocytopenia that has been linked to the AstraZeneca vaccine developed with Oxford University researchers. - REUTERS