LONDON – AstraZeneca and Oxford University admitted a production error on Wednesday, raising questions about the preliminary results of their experimental Covid-19 vaccine.
The statement describing the error came days after the company and university described the shots as “extremely effective” and did not mention why some study participants did not receive the first of the two shots as expected.
Surprisingly, the group of volunteers who received the low dose seemed to be better protected than the volunteers who received the two full doses. In the low-dose group, AstraZeneca said, the vaccine seems to be 90 percent effective. In the group receiving two full doses, the vaccine was found to be 62 percent effective. Combined, the drug makers said the vaccine appears to be 70 percent effective. But the way the results have been reported by the companies has led to questions from experts.
The partial results, released on Monday, are the results of a large ongoing study to determine the optimal dosage of the vaccine in the UK and Brazil, as well as to investigate safety and efficacy. Multiple combinations and doses were attempted among the volunteers. They were compared to others who had been given the meningitis vaccine or saline shot.
Did the researchers mean half a dose?
Before they begin their research, scientists spell out the steps they are taking, and how they will analyze the results. Any deviation from that protocol could call into question the results.
Some of the vials used in the trial did not have the concentration of the vaccine so some volunteers received half the dose, Oxford University said in a statement Wednesday. The university said it discussed the issue with regulators, and agreed to complete a late-stage hearing with the two groups. The production problem has improved, according to the statement.
What about the results themselves
Experts say the relatively small number of people in the low-dose group makes it difficult to know whether the effectiveness seen in the group is real or statistical discretion. About 2,741 people received half the dose of the vaccine, followed by the full dose, AstraZeneca said. A total of 8,895 people received two full doses.
Second factor: None of the low-dose groups were over 55 years of age. Younger people tend to mount a stronger immune response than older people, so this may be why young people participating in the low-dose group looked more effective, not the dose size.
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Another point of confusion comes from the decision to meet the results of two groups of participants who achieved different dosing levels to reach an average effectiveness rate of 0%, said David Salisbury, and a global health program associate at Chatham House think tank.
“You’ve taken two studies for which different doses were used and came up with a joint that doesn’t represent both doses,” he said of the figure. “I think a lot of people are having trouble with it.”
Why would small be more effective?
Oxford researchers say they are not sure and they are working to uncover the cause.
Sarah Gilbert, one of the Oxford scientists who led the research, said the answer was probably to provide the right amount of vaccine to stimulate the best immune response.
“That’s the amount of goldilks you want. I don’t think it’s too little or too much. It can also give you poor quality feedback, “he said. “So you just want the right amount and it’s going to be a bit of a hit when you’re trying to go that fast the whole time.”
What are the next steps?
Details of the trial results will be published in a medical journal and provided to UK regulators so they can decide whether to authorize vaccine delivery. Those reports will include detailed breakdowns including demographics and other information about who fell ill in each group, and will provide a complete picture of how effective the vaccine is.
U.S. Monsef Sloy, who spearheaded the coronavirus vaccine program War Operations, said in a call to reporters on Tuesday that U.S. officials were trying to determine who produced the vaccine, and that the United States might decide to halve the Strazeneca study. Dosage.
“But we want it to be based on data and science,” he said.
