Pfizer and BioNTech’s Covid-19 vaccine starts to work within about 10 days of the first dose, according to new documents released by the US regulator ahead of an advisory meeting this week to discuss whether to grant it emergency approval.

Data released by the US Food and Drug Administration on Tuesday confirmed the vaccine had an efficacy rate of 95 per cent on average, with 93.8 per cent in participants over 55. It also showed Covid-19 cases began to taper off among those who had been vaccinated after just over a week, raising hopes that the inoculation could help ease pressures on overwhelmed hospitals soon after it is rolled out.

The data was released two days before a committee of scientific experts review the case for authorising the vaccine and make a recommendation to the FDA.