Covid: Three month gap between Oxford/AstraZeneca vaccine doses increases efficacy compared to six weeks, study suggests

A longer gap between AstraZeneca jabs results in a higher efficacy, a study has found. Credit: PA

A three month gap between doses of the Oxford/AstrZeneca coronavirus vaccine results in a higher efficacy than a six-week gap, a study has found.

The University of Oxford found that there was an overall efficacy of the vaccine of 81% when the first and second jabs were given three months apart.

This compares to 55% protection when the second doses were given after a six-week interval.

A single dose of the AstraZeneca vaccine offers 76% protection against Covid-19 from 22 days after vaccination, and that this had not waned by the three-month mark, according to the research published in The Lancet.

The UK policy of leaving up to 12 weeks between doses also resulted in a higher efficacy overall, the study found.

The Oxford team is still urging people to have two doses of the vaccine because they say it is not yet clear how long protection with a single dose may last.

Scientists are urging people to have two doses of the vaccine to increase its protection levels. Credit: PA

Top scientific advisers said vaccines were having an impact on the pandemic, as Prime Minister Boris Johnson prepares to publish his road map out of lockdown on Monday.

Professor Adam Finn, from the University of Bristol and a member of the Joint Committee on Vaccination and Immunisation (JCVI), said “everything’s moving in the right direction” when it comes to how jabs are working.

He told BBC Radio 4’s Today programme: “We’ve now got to the point with the study we’re doing in Bristol where we can say with certainty that there is definitely an effect.

“It’s just hard to put an exact number on it at this point because… the numbers of cases coming through are still building up, the number of people who’ve been vaccinated are still going up, but it’s becoming clearer for the Pfizer vaccine, which we’ve been using for a month longer, since early December, and it’ll take slightly longer for us to get a firm handle on just how well the AstraZeneca vaccine is preventing hospitalisations too, but they’re definitely doing the job.”

Professor Neil Ferguson, from Imperial College London, said the data on vaccine effectiveness and how quickly infection, deaths and hospital cases were declining across the country was looking promising.

He said he thought the current lockdown should be lifted in stages, adding:”I am encouraged by the cautious approach being taken, an incremental approach which I think will be adopted, namely relax one thing and see what the impact is, relax again.

“And it still may well be that by the end of May, we’re in a very different country than we are today.”

The UK met its 15m first dose target earlier this month. Credit: PA

Last month, AstraZeneca agreed to supply nine million additional doses of its vaccine to the European Union following a row over the bloc's vaccination programme.

The EU is far behind the UK and the United States in getting its population of 450 million vaccinated against coronavirus.

The slow rollout has been blamed on a range of national problems as well as delayed approval of the vaccines compared to elsewhere and an initial shortage of supply.

This month, the UK passed its 15 million target for first doses administered for the top four priority groups.

More than 16 million people in the UK have been given a first dose of a Covid-19 vaccine and 573,724 second doses have been administered.