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Concern is mounting about the way Oxford University and AstraZeneca have handled early reading of trials for their coronavirus vaccine, which much of the developing world can rely on to emerge from the pandemic.
The results were hailed as a success for showing an average efficacy of 70 percent, a figure that was achieved by combining the results of the cohorts in two different dosing regimens.
Within a month of each other, one group of participants received two identical doses, while the other group received a half dose and then a full dose. The efficacy for the first largest group was 62 percent. In the second subgroup, it was 90 percent.
But on Tuesday, Moncef Slaoui, head of Operation Warp Speed, the U.S. government’s funding program for vaccine development, revealed that the second subgroup was limited to people 55 and younger, a demographic with less risk of developing severe Covid-19.
Oxford and AstraZeneca did not disclose the age breakdown on Monday, when the results were released.
“There are a number of variables that we need to understand,” Slaoui said. It’s still possible that the difference in efficacy is “random,” he added.
The markets have taken notice. London-listed AstraZeneca shares have lost more than 6 percent after the announcement. By comparison, since its vaccine trial results were released earlier this month, showing 90 percent effectiveness, shares in Pfizer and BioNTech have gained 6 and 14 percent; respectively; Moderna is up 11 percent since the vaccine trial data was released, in addition to big strides in the lead-up to release.
One of the early critics this week, Geoffrey Porges, an analyst at SVB Leerink, said he thought the AstraZeneca jab was unlikely to gain approval in the US after the company “tried to embellish its results.” highlighting greater efficiency in a “relatively small subset”. of subjects in the study ”.
John LaMattina, former president of Pfizer’s global research and development unit, said in a cheep It was “hard to believe” that US regulators issued an emergency use authorization for a “vaccine whose optimal dose has only been administered to 2,300 people.”
Much of the confusion is due to Oxford and AstraZeneca not being fully forthcoming about the reason for the two different dosing regimens, which changed unexpectedly as the trials progressed.
In a statement late Wednesday, Oxford acknowledged that a difference in manufacturing and measurement processes meant that later phases of its clinical studies resulted in the administration of half doses rather than a full one.
Wednesday’s statement said this was discussed with regulators at the time, who agreed to use two test regimes. “Methods for measuring concentration are now established and we can ensure that all vaccine lots are now equivalent,” he said.
Richard Lawson, a UK trial participant who does not yet know whether he received the vaccine or a placebo because the trial has yet to be unmasked, told the Financial Times that he was informed of the confusion in July, before receiving a booster shot. .
As a general rule, vaccinologists usually aim for the lowest dose that is still effective, but the efficacy of the lowest dose is not yet explained. Oxford professor Sarah Gilbert has said that a smaller starting dose may prime the immune system in a way that better mimics natural infection. But there is no precedent for other vaccines to be given this way.
“We just don’t have all the information we need to know if these results are reliable,” said Natalie Dean, assistant professor of biostatistics at the University of Florida. “We certainly don’t have enough information in the public domain to decide if this half dose is really working.”
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Professor Dean contrasted the AstraZeneca disclosures with those of other trials. “We had this precedent set by the other vaccines with Moderna and Pfizer / BioNTech and these were individual trials, with a published protocol in advance,” he said. “We had the opportunity to review it. . . It was pretty straightforward. “
There are also concerns about variations in the Oxford vaccine trial in different countries. In addition to the different dosing regimens, there were also differences between control groups in different countries: in the UK, participants who did not receive the Covid vaccine were given a meningococcal vaccine; in Brazil they received a saline placebo.
These discrepancies have led to the suggestion that the data are too patchy to combine into a single convincing efficacy result.
An AstraZeneca spokesperson defended the trial, saying it was “conducted to the highest standards” and met its primary efficacy endpoint. The company has said that more data will continue to be accumulated and further analysis will be conducted, refining the efficacy reading and establishing how long the vaccine protects against the virus.
The results will appear in a peer-reviewed journal, and regulators have set a 50 percent efficacy threshold, meaning that a 70 percent effective jab would still be approved.
Despite doubts about efficacy, the Oxford / AstraZeneca vaccine offers some indisputable benefits. It is cheaper than Moderna and Pfizer / BioNTech mRNA vaccines and can be stored in a refrigerator rather than a freezer.
The University of Oxford said it “fully” understood the interest in the discovery of the dosing error and the change in dosing tactics, which was approved by UK regulators.
“As this is a complicated scientific area, our scientists would like to wait until the peer-reviewed publication of the interim Phase 3 results in The Lancet. [medical journal] Before we discuss this further, what we anticipate will be in the coming weeks, ”he said.
Additional reporting by Hannah Kuchler in New York and Kiran Stacey in Washington
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