The Oxford/AstraZeneca Covid vaccine may reduce transmission by 67%, a new study has suggested.
The vaccine also shows ‘sustained protection’ of 76% during the 12 weeks between doses, according to the unpublished study.
The University of Oxford last night announced that its new analysis of vaccine trial data suggests the vaccine may have a ‘substantial effect on transmission’.
The analysis, which is currently under review at The Lancet, found that there was a 67% reduction in positive PCR swabs among those vaccinated.
Researchers at the University of Oxford analysed additional data from the UK trial up to 7 December 2020, including a further 201 cases of ‘primary symptomatic Covid-19’ compared with the 131 reported previously.
The study also found that a single ‘standard’ dose of the Oxford vaccine was 76% effective from 22 to up to 90 days after vaccination, with protection ‘not falling’ in the three-month period.
It revealed that vaccine efficacy is ‘higher at longer prime-boost intervals’ – with efficacy rising from 55% with a dose gap of fewer than six weeks compared with 82% after the second standard dose at a 12-week interval.
Chief investigator of the Oxford vaccine trial and co-author of the paper Professor Andrew Pollard said: ‘These new data provide an important verification of the interim data that was used by more than 25 regulators including the MHRA and EMA to grant the vaccine emergency use authorisation.
‘It also supports the policy recommendation made by the Joint Committee on Vaccination and Immunisation (JCVI) for a 12-week prime-boost interval, as they look for the optimal approach to roll out, and reassures us that people are protected from 22 days after a single dose of the vaccine.’
Official guidance changed on 31 December to say all second doses should be given after 12 weeks instead of three weeks to maximise the number of people protected against Covid-19 in the shortest possible timeframe.
Health secretary Matt Hancock yesterday said he had a ‘high degree of confidence’ that the UK’s vaccine supply and logistics would enable patients to get the ‘right’ second dose at the right time.
Meanwhile, the Oxford University researchers hope to report on data regarding the new variants in the coming days, with findings expected to be ‘broadly similar to those already reported by fellow vaccine developers’, they added.
Also last month, Public Health England said it would call upon GPs as it launched a study into the effects of Covid vaccination, including whether it stops virus transmission.