LONDON – AstraZeneca and the University of Oxford on Wednesday acknowledged a manufacturing defect that raises questions about the preliminary results of their experimental Covid-19 vaccine.
The statement describing the error occurred days after the company and the university rated the recordings as “extremely effective” and did not mention why some study participants did not receive as many vaccinations in the first of the two shots as expected.
Surprisingly, the group of volunteers who received the lower dose seemed to be much better protected than the group of volunteers who received two full doses. According to AstraZeneca, the vaccine appeared to be 90 percent effective in the low-dose group. In the two full-dose groups, vaccination appeared to be 62 percent effective. Combined, the drug manufacturers said the vaccine appeared to be 70 percent effective. But the way the results were achieved and reported by the companies raised expert questions.
The partial results announced on Monday come from large, large studies in the UK and Brazil aimed at determining the optimal dose of the vaccine and examining its safety and effectiveness. Several combinations and doses were tested in volunteers. They were compared with others who had been vaccinated against meningitis or saline.
Did the researchers want to give half a dose?
Before they begin their research, scientists articulate all the steps they will take and how they will analyze the results. Any deviation from the protocol may call the results into question.
Oxford University said in a statement on Wednesday that some of the vials used in the study did not have adequate vaccine concentrations, so some volunteers received doses. The university said it had discussed the issue with regulators and agreed to complete negotiations on the late stage with two groups. According to the statement, the manufacturing problem has been fixed.
What about the results themselves
Experts say the relatively small number of people in the low-dose group makes it difficult to see if the efficacy seen in the group is real or a statistical oddity. About 2,741 people received a dose of the vaccine followed by a full dose, AstraZeneca said. A total of 8,895 people received two full doses.
Another factor was that none of the people in the low-dose group were older than 55 years. Younger people generally elicit a stronger immune response than older ones, so it may be that, due to the youth of the participants in the low-dose group, this seemed to be more effective than the dose size.
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Another point of confusion is the decision to pool the results of two groups of participants who were given different dosage levels to achieve an average efficacy of 70 percent, said David Salisbury, of the Global Health Program at Chatham House Brain Trust.
“He did two studies that used different doses and produced a composite that didn’t represent either dose,” he said of the figure. “I think a lot of people have trouble with that.”
Why would a smaller first be more effective?
Oxford researchers say they are unsure and are working to find out the cause.
Sarah Gilbert, the lead Oxford scientist in the research, says the answer is probably related to whether they provide exactly the right amount of vaccine to elicit the best immune response.
“I think Goldilocks wants an amount, not too little and not too much.” Too many poor quality answers can also give you, “he said.” So you want just the right amount, and it’s a bit hit and miss when you want to get it fast to be perfect the first time. “
What are the next steps?
Details of the test results will be published in medical journals and communicated to UK regulators for a decision on whether to allow the vaccine to be marketed. These reports include a detailed breakdown that includes demographic and other information about who became ill in each group and provide a more complete picture of vaccination effectiveness.
Moncef Slaoui, head of the U.S. coronavirus vaccine program for Operation Warp Speed, told reporters on Tuesday that U.S. officials are trying to determine what immune response the vaccine elicits and may decide to modify AstraZeneca in the U.S. study half of it. dose.
“But we want it to be based on data and science,” he said.