UK nods to AstraZeneca vaccine raise more questions

A vaccine labeled with a test tube is seen in front of the AstraZeneca logo in this illustration on September 9, 2020.

Dado Ruvic | Reuters

British health officials eased the AstraZeneca and Oxford Covid-19 shot on Wednesday, but also refuted one of their central allegations: that a half-dose followed by a standard dose provides more protection against infection.

The re-evaluation of the best dose regimen for the vaccine was an unexpected move by the UK Drug Regulator, based on its own analysis of as yet unpublished data, and it raised new questions about the efficacy of a vaccine still available in other countries. must be approved. .

Although cheaper and easier to distribute than competitive surveys, the Oxford / AstraZeneca vaccine has been plagued by uncertainty about the most effective dose since data published last month showed that half a dose followed by a full dose achieved 90% success , while two full shots were 62% effective.

Oxford researchers said the more successful outcome was an ‘intriguing result’ that deserves further testing.

However, a Reuters investigation found that the existence of the low-dose / standard-dose arm was the result of a strong miscalculation by Oxford researchers, which called into question the robustness of the result.

Munir Pirmohamed, chairman of a British advisory group for Covid-19 vaccines, confirmed the doubt on Wednesday, saying the 90% efficacy rate was not kept at the analysis.

Instead, Pirmohamed said a higher success rate may be due to a longer gap between the administration of the first and second hold.

“The low-dose / standard-dose regimen, although cited for 90% efficacy, is confused by the fact that the interval between the first and second doses was quite long,” Pirmohamed told a news conference.

“And we feel that the result may be related to the interval, rather than the dose itself,” he said.

The British Covid-19 vaccine chair, Wei Shen Lim, said that a single dose of Oxford / AstraZeneca vaccine was approximately 21% effective from 21 days until a second dose was given.

Pirmohamed said the success rate of the AstraZeneca / Oxford vaccine could increase to 80% if the three-month gap is left rather than a one-month gap between doses.

After British health officials released the new details on the vaccine’s effectiveness, a spokesman for AstraZeneca said: “It is up to the regulators to authorize how the vaccine should be used.”

‘Factors they took into account include the comparable immunogenic response to two doses with one of the two treatments, as well as the protection against serious diseases (100%),’ he said.

“We believe we have approved the best vaccination strategy by the MHRA.”

A ‘winning formula’

Faced with a record-breaking increase in infections caused by a highly contagious variant of the virus, Britain gives priority to giving a first dose of a vaccine to as many people as possible over giving second doses. Delaying the distribution of second shots can increase supply.

The UK Regulatory Agency for Medicines and Health Care Products (MHRA) has recommended an interval of between 4-12 weeks between doses of AstraZeneca / Oxford vaccine and has also updated the guidelines for a second dose of Pfizer-BioNTech shot and stated that within 12 weeks can be administered, rather than the 21 days originally recommended.

Hundreds of thousands of Britons have already received their first dose of Pfizer vaccine after the UK became the first country to approve the rollout, with the second doses available this week.

Pfizer sounds cautious about the prospect of shifting the schedule of its second dose, noting that it has not been evaluated on different dosing schedules.

“There is no evidence to show that protection is maintained after the first dose after 21 days,” the statement said, adding that the implementation of alternative schedules should be closely monitored.

“Although decisions on alternative administration regimens rest with health authorities, Pfizer believes it is critical … to ensure that each recipient receives the maximum possible protection, which means immunization with two doses of the vaccine.”

Pascal Soriot, CEO of AstraZeneca, is quoted in the Sunday Times newspaper as saying that his firm has a ‘winning formula’ for demonstrating efficiency rates of around 95% through vaccinations developed by Pfizer and Moderna. He said he could not say more pending the publication of new data.

In an interview with Sky News, Sarah Gilbert, Oxford’s vaccine developer, said there was transparency in the process.

“The MHRA said they would publish their assessment report. There are different groups in the trial; we had different intervals between the doses and different dose levels as you say, and that makes the analysis a bit complicated,” she said. said.

“The MHRA has done their own analysis, and they are very confident in licensing the vaccine now for emergency use.”

Oxford did not respond to a request for comment after the MHRA briefing.

Regulators in other countries have taken a more cautious approach than Britain, and the various efficacy figures cited by the MHRA, as well as the new recommendations on the timing of second doses, have urged scientists to release the details in support of the approval. .

“More needs to be known because many points about these decisions are unclear. MHRA and JCVI have promised to provide more information urgently,” said Saad Shakir, director of the Drug Safety Research Unit near Southampton.

Jeremy Farrar, director of the Wellcome Health Research Foundation, said a new trial would be needed to provide clearer data on the best timing of a second dose.

“We will also need to continue to track and improve our understanding of how long the protection lasts and whether it can prevent transmission,” he said.

“This will be best achieved through a randomized trial with the timing of the second dose.”

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