A new study has found that one shot of the Oxford/AstraZeneca or Pfizer/BioNTech vaccine reduces coronavirus infections by nearly two-thirds and protects older and more vulnerable people as much as younger, healthy individuals.

The results from Oxford University and the Office for National Statistics are a welcome boost to the vaccination programme and the first to show the impact on new infections and immune responses in a large group of adults in the general population.

The researchers analyzed Covid test results from more than 350,000 people in the UK between December and April. They found that 21 days after a first jab – the time it takes the immune system to mount a decent response new Covid infections dropped by 65%.

Scientists on the team said the findings supported the UK’s decision to prioritise giving first shots to elderly and more vulnerable people by delaying second doses. There is no evidence that the vaccines are less effective among older adults or those with long-term health conditions.