UK nod to AstraZeneca vaccine raises more questions

British health officials gave the green light on Wednesday for the AstraZeneca and Oxford Covid-19 shot, but also rebutted one of their central claims: that a half dose followed by a standard dose provided more protection against infection.

The reassessment of the best vaccine dosing regimen was an unexpected step by the UK medicines regulator based on its own analysis of unpublished data and raised new questions about the efficacy of a vaccine that has yet to be approved in other Nations .

Although cheaper and easier to distribute than rival injections, the Oxford / AstraZeneca vaccine has been plagued with uncertainty as to the most effective dosage since data published last month showed that a half dose followed by a full dose had a 90% success rate, while two full shots were 62% effective.

Oxford researchers said the more successful outcome was an “intriguing result” that needed further testing.

However, a Reuters study found that the existence of the low dose / standard dose arm was the result of a potency miscalculation by Oxford researchers, calling into question the robustness of the result.

Munir Pirmohamed, chair of a UK advisory group on Covid-19 vaccines, confirmed those concerns Wednesday, saying the 90% efficacy under analysis did not hold up.

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

“Although the low-dose / standard-dose regimen is said to have 90% efficacy, this is interfered with by the fact that the interval between the first and second dose was quite long,” Pirmohamed told a news conference.

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

UK Covid-19 vaccine chairman, Wei Shen Lim, said a single dose of Oxford / AstraZeneca’s vaccine was about 70% effective from 21 days until a second dose was given.

Pirmohamed said leaving the three-month difference instead of a month between doses could increase the success rate of the AstraZeneca / Oxford vaccine by up to 80%.

After UK health officials revealed new details about the vaccine’s efficacy, an AstraZeneca spokesperson said, “It is up to regulators to authorize how the vaccine should be used.”

“Factors that they will have taken into account include the comparable immunogenic response after two doses with each regimen, as well as protection against severe disease (100%),” he said.

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

Faced with a record increase in infections caused by a highly contagious variant of the virus, Britain is prioritizing giving the first dose of a vaccine to as many people as possible over giving a second dose. Delaying the distribution of second shots would help stretch the supply.

The UK Medicines and Healthcare Products Regulatory Agency (MHRA) recommended an interval of 4-12 weeks between doses of the AstraZeneca / Oxford vaccine and also updated its guidelines for a second dose of the Pfizer-BioNTech injection, stating that it is within 12 weeks could be administered instead of the originally recommended 21 days.

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

Pfizer sounded cautious at the prospect of shifting the second dose schedule, noting that it had not been evaluated on different dosing schedules.

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

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

AstraZeneca CEO Pascal Soriot was quoted in the British Sunday Times newspaper as saying his company had a “winning formula” that rivaled the approximately 95% efficacy rates demonstrated by vaccines developed by Pfizer and Moderna. He said he could say no more pending the release of new data.

Speaking to Sky News, Oxford vaccine developer Sarah Gilbert said the process was transparent.

“The MHRA have said they will publish their assessment report. There are different groups within the study, we have different intervals between doses and different dose levels as you say, and that makes the analysis somewhat complicated,” she says. said.

“The MHRA has done their own analysis and they are confident that they are now licensing the vaccine for emergencies.”

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

Regulators in other countries have taken a more cautious approach than Britain, and the different efficacy rates cited by the MHRA, as well as the new recommendations on the timing of second doses, have prompted scientists to explore the details underlying the approval, to release.

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

Jeremy Farrar, director of Wellcome health research foundation, said a new trial may be needed to get clearer data on the best timing of a second dose.

“We will also need to continue to monitor and improve our understanding of how long protections last and whether they can prevent transmission,” he said.

“This is best accomplished by a randomized study of the timing of the second dose.”