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LONDON (AP) – AstraZeneca and the University of Oxford on Wednesday admitted a manufacturing error that raises questions about the preliminary results of their experimental COVID-19 vaccine.
A statement describing the error came days after the company and the university described the vaccines as “very effective” and did not mention the reasons why some study participants did not receive so much. vaccine than expected with the first of the two injections.
In a surprise, the group of volunteers who received a lower dose appeared to be much better protected than the volunteers who received two full doses. In the low dose group, AstraZeneca said the vaccine appeared to be 90% effective. In the group that received two full doses, the vaccine appeared to be 62% effective. Together, the drug makers said the vaccine appeared to be 70 percent effective. But the way the results were obtained and reported by the companies led to some pointed questions from experts.
The partial results announced on Monday come from large studies underway in the UK and Brazil to determine the optimal dose of vaccine, as well as to examine safety and effectiveness. Multiple combinations and doses have been tried in volunteers. They were compared to others who received a meningitis vaccine or an injection of saline.
DID RESEARCHERS WANT TO GIVE A HALF-DOSE?
Before starting their research, scientists explain all the steps they take and how they will analyze the results. Any deviation from this protocol may call into question the results.
In a statement Wednesday, the University of Oxford said some of the vials used in the trial did not have the correct concentration of vaccine, so some volunteers were given half a dose. The university said it had discussed the issue with regulators and agreed to complete the advanced stage trial with two groups. The manufacturing problem has been corrected, the statement said.
WHAT ABOUT THE RESULTS?
Experts say the relatively small number of people in the low-dose group makes it difficult to know whether the efficacy seen in the group is real or a statistical oddity. Some 2,741 people received a half-dose of the vaccine followed by a full dose, AstraZeneca said. A total of 8,895 people received two full doses.
Another factor: none of the people in the low dose group were over 55 years old. Younger people tend to develop a stronger immune response than older people, so it could be that the young in the low-dose group participants were the reason it seemed more effective, not the size of the dose.
Another point of confusion comes from a decision to pool the results of two groups of participants who were given different dosage levels to achieve an average efficiency of 70%, said David Salisbury, and associate member of the Global Health Program. at Chatham House Think Tank.
“You took two studies where different doses were used and you came up with a composite that doesn’t represent any of the doses,” he said of the figure. “I think a lot of people have problems with that.”
WHY WOULD A SMALLER FIRST DOSE BE MORE EFFECTIVE?
Oxford researchers say they are not sure and are working to find out why.
Sarah Gilbert, one of the Oxford scientists leading the research, said the response was likely related to providing exactly the right amount of vaccine to trigger the best immune response.
“This is the amount of Goldilocks you want, I guess, not too much and not too little. Too much could also give you a shoddy response, ”she said. “So you just want the right amount and it’s a bit hit and miss when you’re trying to go fast to get the perfect first time.”
WHAT ARE THE NEXT STEPS?
Details of the trial results will be published in medical journals and provided to UK regulators so they can decide whether or not to allow the vaccine for distribution. These reports will include a detailed breakdown including demographic and other information on who fell ill in each group, and give a more complete picture of the vaccine’s effectiveness.
Moncef Slaoui, who heads the U.S. Operation Warp Speed coronavirus vaccine program, said on a call with reporters on Tuesday that U.S. officials were trying to determine what immune response the vaccine produced and may decide to modify the study AstraZeneca in the United States to include half of it. dose.
“But we want it to be based on data and science,” he said.
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