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AstraZeneca and the University of Oxford today acknowledged a manufacturing error that is raising questions about the preliminary results and effectiveness of their experimental COVID-19 vaccine.
The statement, acknowledging the mistake, comes days after the company and the university rated the vaccine as “highly effective,” not to mention why some participants in clinical trials did not receive the same amount of vaccine in the first of the two. injection, as expected, reports the AP agency.
Surprisingly, the group of volunteers who received one lower dose appeared to be much more protected than the volunteers who received two full doses.
In the low-dose group, AstraZeneca said, the vaccine appears to be 90% effective, while in the group that received two full doses, the effectiveness appears to be 62%.
With these results combined, the manufacturers revealed that the vaccine appears to be 70% effective, but how they were obtained raised questions from experts.
The partial results announced Monday are the result of ongoing massive clinical trials in the UK and Brazil designed to determine the ideal dose of the vaccine, as well as to examine safety and efficacy.
Various combinations and doses were administered to the volunteers and the results were compared with others who received a meningitis vaccine or saline solution.
Before starting the trials, the researchers explained all the steps to take and how to analyze the results. Any deviation from this protocol can jeopardize the results.
In a statement issued Wednesday, the University of Oxford said that some of the vials used in the test did not have the proper concentration of vaccine, meaning that some volunteers received half doses.
The university added that it discussed the issue with regulators and agreed to complete the test. The manufacturing issue was corrected, according to the statement.
For experts, the relatively low number of people in the low-dose group makes it difficult to understand whether the observed effectiveness in the group is real or a statistical peculiarity.
About 2,741 people received half a dose of the vaccine followed by a full dose, AstraZeneca revealed, with a total of 8,895 people receiving both full doses.
Another factor at play is the fact that none of the participants in the low-dose group is over 55 years old, and younger people tend to have a stronger immune response than older people.
The discussion is still the union of the two participating groups that received different dosage levels to achieve an average effectiveness of 70%, said one of the members of the Chatham House global health program, David Salisbury.
One of the Oxford scientists leading the research believes that the greater efficacy in the group that took the reduced dose may be related to providing the exact amount of vaccine to trigger the best immune response.
“Not too little, not too much. Too much can also give a low-quality response,” he said.
Details of clinical trial results will be published in medical journals and provided to UK regulators, who will decide on marketing authorization for the vaccine.
These reports will include a detailed analysis with demographic information or information on who got sick in each group, which will provide a more complete picture of the vaccine’s effectiveness.
The covid-19 pandemic caused at least 1,415,258 deaths derived from more than 60 million cases of infection worldwide, according to a report prepared by the French agency AFP.
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