(Reuters) - An additional global trial to test the effectiveness of its COVID-19 vaccine using a lower dose is likely to be conducted by AstraZeneca, its chief executive was quoted as saying on Thursday amid concerns about the outcome of its late-stage review.
AstraZeneca could start a new study to test a lower dose of its vaccine that worked better than a full dosage, Pascal Soriot told Bloomberg News, instead of adding the trial to an existing U.S. phase.
"We have to validate this now that we have discovered what looks like a better efficacy, so we need to do an additional study," he said, adding that the latest, likely global, study could be quicker because it would require less subjects as the effectiveness was already established to be high.
The news comes as AstraZeneca faces concerns about its success rate that some analysts claim could impede its chances of securing rapid regulatory approval from the U.S. and EU.
Several scientists have raised concerns about the robustness of the findings published on Monday showing that 90 percent of the experimental vaccine was successful in a subgroup of study participants who received a half dose followed by a full dose by mistake initially.
He did not expect the extra trial to delay British and European regulatory approvals, Soriot said.
An AstraZeneca spokesman, asked about the Bloomberg study, said there was strong merit in continuing to examine the half-dose/full dose protocol. To those from current trials that are being prepared for regulatory submission, he said, any more findings from the data will be added.
For the British drugmaker in the race to produce a vaccine to help tame the pandemic, which killed more than a million people and roiled the global economy, running an extra trial might not be too much of a complication.
Helen Fletcher, Professor of Immunology at the London School of Hygiene & Tropical Medicine, said another trial would not necessarily prolong having a green light because the World Health Organization's goal was still fulfilled by efficacy in the higher dose regime. The launch of new research on licensed vaccines was not unprecedented, she said.
Before the end of the year the vaccine is one of three that may be accepted. Pfizer and Moderna announced this month that their vaccines were around 95 percent efficient in disease prevention, setting the bar sky-high.
Even so, Oxford University's AstraZeneca shot is cheaper to produce, simpler to sell, and quicker to scale up than its opponents.
On Friday, Britain asked its medicine regulator to determine whether the applicant for the vaccine met stringent safety requirements with a view to temporary delivery, a step towards launching the vaccine roll-out before the end of the year.
By the end of next month, AstraZeneca expects 4 million doses to be available in Britain.
In the coming weeks, a peer-reviewed study of evidence from the current trial will be published in a medical journal.
Requests for comment were not received immediately by the European Medicines Agency.
AstraZeneca informed Reuters earlier on Thursday that the half-dose administration had been checked and approved by independent data protection monitors and the British regulator, adding that no concern" was publicly reported by the regulator.
Clearance by the U.S. However the Food and Drug Administration (FDA) could take longer, since the agency is unlikely to approve the vaccine on the basis of studies performed elsewhere, especially given concerns about the outcomes, Soriot said.
On Monday, AstraZeneca research chief Mene Pangalos told Reuters that the company will begin discussions with the FDA to modify the design of its trial to incorporate a more efficient dosage scheme.
Authorisation is also needed before the end of the year in some countries.
In many nations, Astrazeneca has signed deals to supply vaccines, including 120 million doses to Japan and 85 million doses to Australia.
Talking to the media, Australian Prime Minister Scott Morrison expressed confidence in the vaccine being developed by the country's biomedical giant, CSL Ltd.
The Serum Institute of India is carrying out vaccine trials there.
Even the lowest efficacy results, making it a viable virus vaccine, are at 60-70 percent," the institute said in a statement, adding that the studies were running smoothly."
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