LONDON — AstraZeneca and Oxford University have more work to do to confirm whether their COVID-19 vaccine can be 90% effective, a peer-reviewed paper in The Lancet showed on Tuesday, potentially slowing its rollout in the fight against the pandemic.
Once seen as the frontrunner in the development of a vaccine against the coronavirus crisis, the British team was overtaken by US drugmaker Pfizer, whose shots – with a success rate of around 95% – were administered to UK pensioners on Tuesday in a world-first hailed as V-Day.
Detailed results from the AstraZeneca/Oxford vaccine trials have been eagerly awaited after some scientists criticized a lack of clarity in an initial announcement last month.
But the Lancet publication gave few extra clues as to why efficacy was 62% for trial participants given two full doses, but 90% for a smaller sub-group given a half, then a full dose.
“(This) will require further research as more data becomes available from the trial,” the researchers said.
John Moore, virologist at Weill Cornell Medical College in New York, said the team’s Lancet paper was “a hotchpotch of factoids and is hard to digest.”
Ian Jones, a professor of virology at Reading University in England, said that while Tuesday’s data added “flesh to the bones” of the release last month, “further trial data might be needed to explain why the lower dose group was significantly better protected than the standard dose group.”
Asked whether the half, then full dose regimen had been a mistake, Andrew Pollard, director of the Oxford Vaccine Group and chief investigator into the trials, said it had been “unplanned.”
Less than 6% of UK trial participants were given the lower dose regimen and none of them was aged over 55, meaning more studies will be needed to investigate the vaccine’s efficacy in older people who are particularly susceptible to COVID-19.
Pooling the results, overall efficacy was 70.4%, the data on Tuesday showed. That is above the 50% minimum set by the US Food and Drug Administration. – Reuters