The UK goal for AstraZeneca vaccine raises more questions

British health officials stressed the AstraZeneca and Oxford Covid-19 bullet on Wednesday but reiterated one of their main claims: that half-doses and standard doses offered greater protection against infection.

The reassessment of the optimal dosing regimen for the vaccine was an unexpected move by the British medicines regulator based on its own analysis of as yet unpublished data and raised new questions about vaccine efficacy not yet agreed in other countries. .

Although cheaper and easier to circulate than competitive strains, the Oxford / AstraZeneca vaccine has been uncertain about the most effective dose ever since data released last month showed that half dose and full dose had a 90% success rate while two full shots were 62% effective.

Researchers from Oxford said the more successful result deserved “interesting results” that deserved further testing.

A Reuters study, however, found that the low-dose / normal-dose arm was the result of a strong misconception by researchers from Oxford, questioning the strength of the result.

Munir Pirmohamed, chairman of a British advisory group on Covid-19 vaccines, confirmed these doubts on Wednesday saying the 90% effectiveness rate did not stand under scrutiny.

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

“The low dose / standard dose schedule, although said to have a 90% efficacy, is confirmed by the fact that the interval between the first and second doses was very long,” said Pirmohamed at co. press conference.

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

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

Pirmohamed said leaving the gap of three months rather than a gap of one month between doses could raise the success rate of the AstraZeneca / Oxford vaccine to 80%.

After British health officials released the new details about the effectiveness of the vaccine, an AstraZeneca spokesman said: “It is up to the regulators to authorize how the vaccine should be used.”

“Among the factors they will have taken into account is the relative immunogenic response after two doses with the second regimen, as has the protection against severe disease (100%),” he said.

“We believe our best vaccination strategy has been agreed with the MHRA.”

With a higher rise in infections transmitted by a large infectious strain of the virus, Britain is prioritizing getting the first dose of vaccine for as many people as possible over the second half. give doses. Delays in circulating second strokes would help to extend the supply.

The British Medicines and Healthcare products Regulatory Agency (MHRA) recommended a 4-12 week interval between doses of the AstraZeneca / Oxford vaccine and also updated their guidelines for a second dose of the Pfizer-BioNTech image. be administered within 12 weeks. , rather than the 21 days originally proposed.

Hundreds of thousands of Britons have already received the first dose of the Pfizer vaccine after the UK sent in the first country to roll it out, with a second dose due this week.

Pfizer was cautious about shifting its second dose schedule, noting that it had not been evaluated on different dosing schedules.

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

“While decisions about other dosing regimens remain with health authorities, Pfizer believes it is crucial … to ensure that all recipients receive the greatest possible protection, which means vaccine with two doses of the vaccine. “

AstraZeneca CEO Pascal Soriot was quoted in the British Sunday Times newspaper as saying that his company had a “winning formula” to compete with the efficiency levels of around 95% shown. with vaccines developed by Pfizer and Moderna. He said he could say no more until new data is released.

Speaking to Sky News, Oxford vaccine developer Sarah Gilbert said there was transparency in the process.

“The MHRA has said that they will publish their assessment report. There are different groups within the trial, we have had different times between doses, and different dose levels as they say. you, and that makes the analysis a bit complicated, “she said.

“The MHRA have carried out their own analysis, and are now very confident in approving the vaccine for emergency use.”

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

Regulators in other countries have taken a more cautious approach than Britain and the various levels of efficacy announced by the MHRA as well as their new proposals on the timing of second doses have encouraged scientists to ask that the details that form the basis of his consent would be released.

“More needs to be found out as many points about these decisions remain unclear. MHRA and JCVI have promised to provide more information without delay,” said Saad Shakir, Director of the Drug Safety Investigation Unit near Southampton.

Jeremy Farrar, director of health research foundation Wellcome, said a new test may be needed to provide clearer data on the best time for a second dose.

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

“This would be best achieved by a randomized trial at the time of the second dose.”