Late-stage human trials for the Covid-19 vaccine developed by Oxford University and biopharmaceutical company AstraZeneca showed that the vaccine could be up to 90 per cent effective at preventing the disease, the company said yesterday.
A lower dose appeared to be more effective than a higher one, preliminary results showed.
Under the dosing regimen where volunteers were first given half a dose, followed by a full dose at least one month apart, the vaccine efficacy was 90 per cent. But when volunteers were given two full doses at least one month apart, the efficacy was 62 per cent.
The combined analysis from both dosing regimens involving more than 11,000 volunteers resulted in an average efficacy of 70 per cent, AstraZeneca said in a statement.
More data will continue to accumulate and additional analysis will be conducted, it added. This will help to improve the efficacy reading and establish the duration of protection.
Professor Andrew Pollard, chief investigator of the Oxford vaccine trial at the university, said the findings showed that the vaccine was effective. "Excitingly, we have found that one of our dosing regimens may be around 90 per cent effective and if this dosing regime is used, more people could be vaccinated with planned vaccine supply," he added.
In September, AstraZeneca stopped giving shots of its vaccine after a person participating in one of its studies got sick, although the trials were later allowed to resume.
AstraZeneca said in yesterday's statement that no serious safety events related to the vaccine have been confirmed, and that the vaccine was well tolerated across both dosing regimens.
AstraZeneca's chief executive Pascal Soriot said: "The vaccine's simple supply chain and our no-profit pledge and commitment to broad, equitable and timely access means it will be affordable and globally available, supplying hundreds of millions of doses on approval."
Yesterday's update from AstraZeneca comes after Pfizer, BioNTech and Moderna - the companies behind two other Covid-19 vaccine front runners - revealed positive results from their own late-stage trials. The firms have said their vaccines were more than 90 per cent effective at preventing the disease.
Speaking at a virtual press conference, Prof Pollard said it was difficult to explain the differences in the results in the absence of published data sets for the different vaccines.
"We don't know exactly what everyone is measuring in the trials until we have actually got those full data sets out and we can see exactly what everyone has," he said, adding that the researchers behind the Oxford and AstraZeneca vaccine plan to submit their own data for publication in the days ahead.
Oxford University's Professor Sarah Gilbert added that the world would need multiple vaccines because no one developer or manufacturer will be able to produce enough doses to meet global demand.
She added: "It is really excellent to see that the high efficacy that we are now getting out of these trials - coupled with the safety, the ability to manufacture in large doses, the ability to feed into existing distribution networks for vaccines that already are in place around the world - because all of that together is going to really make a difference to get a lot of people vaccinated."
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