London: The Oxford-AstraZeneca COVID-19 vaccine is 67 per cent effective in reducing the spread of the virus after a single shot, a study published in the Lancet said.
A two-dose regimen brings efficacy to 50 per cent.
The vaccine also shows 76 per cent efficacy against symptomatic infection after 90 days of a single shot, AstraZeneca said on Wednesday. The efficacy increased to 82 per cent after inter-dose interval of 12 weeks or more.
This helps support the policy recommendation in the UK to immunize more people at one go by delaying the second dose.
This analysis for efficacy was based on 17,177 participants including 332 symptomatic cases from Phase 3 trials led by Oxford University and AstraZeneca in UK, Brazil and South Africa. It showed that there were no severe cases and no hospitalization, more than 22 days after the first dose.
