COURTESY HT NOV 24

ReutersDosage breakthrough down to serendipity

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FRANKFURT/LONDON : A stroke of good fortune from a dosing error will pave the way for AstraZeneca and Oxford University to submit their Covid-19 vaccine for regulatory clearance.

The British drugmaker said on Monday that the vaccine could be around 90% effective, when administered as a half dose followed by a full dose a month later, citing data from late-stage trials in Britain and Brazil.

“The reason we had the half-dose is serendipity,” Mene Pangalos, the head of AstraZeneca’s non-oncology research and development, told Reuters.

A larger group who had received two full doses - as planned - resulted in an efficacy read-out of 62%, leading to an overall efficacy of 70% across both dosing patterns.

Around the time when AstraZeneca was initiating its partnership with Oxford at the end of April, university researchers were administering doses to trial participants in Britain. They soon noticed expected side effects such as fatigue, headaches or arm aches were milder than expected.

“So we went back and checked ... and we found out that they had underpredicted the dose of the vaccine by half,” said Pangalos. He added the firm decided to continue with the half dose and administer the full dose shot at the scheduled time.

The difference in performance of the vaccine when initial dose was halved was described as intriguing by Andrew Pollard, the director of the Oxford Vaccine Group and chief investigator of the Oxford Vaccine Trial. “I think all of us expected that the two high doses would be the best response. We think that by giving a smaller first dose, that we’re priming the immune system differently. We’re setting it up better to respond,” said Pollard. His colleague, professor Sarah Gilbert, said the better result with a smaller dose could be because this better “mimics what happens in a real infection”