Scientists today said the Oxford University and AstraZeneca jab is more effective if is there is a 12-week gap between doses.
The Covid-19 vaccine has 76 per cent efficacy against symptomatic infection for three months after a single dose. But this improves when a second shot is given later, a preprint study showed on Tuesday.
Oxford University said the findings supported a decision to extend the interval between initial doses and booster doses of the shot to 12 weeks.
The government opted to increase the gap between doses in order to give as many people as possible a first jab. AstraZeneca has welcomed the move, saying flexibility to extend the time between doses is the best strategy for the shot.