Lancet study suggests AstraZeneca vaccine reduces COVID transmission

The Oxford-AstraZenenca COVID-19 vaccine may help to reduce the spread of the virus, according to a study by Oxford University which is set to be published in The Lancet.

The study, Single Dose Administration, And The Influence Of The Timing Of The Booster Dose On Immunogenicity and Efficacy Of ChAdOx1 nCoV-19 (AZD1222) Vaccine, suggests that the vaccine may have a “substantial” effect on transmission of the virus.

The study measured the impact on transmission by testing for asymptomatic infections, swabbing participants every week in addition to recording when anyone fell ill with Covid-19.

As well as showing an effect on transmission, the study found the vaccine offered 76% effective protection from a single dose for three months.

With no fall in protection during the three-month period, the researchers said the results supported gaps between first and second doses of between four and 12 weeks.

The effectiveness of the vaccine increased with a longer gap of 12 weeks before the booster jab.

When the second dose is given, the study found the level of protection from the Oxford-AstraZeneca vaccine rises to 82%.

The study follows criticism of the UK’s dosing strategy from the British Medical Association (BMA), as revealed in a leaked letter to the chief medical officer (CMO) Chris Whitty.

BMA council chair Dr Chaand Nagpaul said the organisation had written to the CMO about the 12-week interval, asking him to “reconsider the decision”.

The BMA  called on the government to “look at guidance from the World Health Organisation” (WHO) and “take stock of the fact that no other nation in the world has adopted the 12-week delay like the UK”.

BMA GP Committee chair Dr Richard Vautrey added that the BMA wants “a dialogue” and “proper scientific enquiry” over the issue, using new data from the vaccination programme.

Official UK 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.

Speaking on BBC Breakfast, the UK’s Health Secretary Matt Hancock he said this latest analysis showing the vaccine reduces transmission would “help us all get out of this pandemic”.

Prof Andrew Pollard, chief investigator of the Oxford vaccine trial, said the results supported the UK’s approach to delaying the booster shot.

It “reassures us that people are protected from 22 days after a single dose of the vaccine,” he says.

Use of the Oxford vaccine has been restricted by French health authorities who say it should only be given to people under 65.

Mr Hancock, the UK health secretary, said scientists had looked directly at the over-65s and there was “a high degree of confidence” that the Oxford vaccine worked on people of all ages.

When the second dose is given, the study found the level of protection from the Oxford-AstraZeneca vaccine rises to 82%.