Manufacturing error raises questions about testing with AstraZeneca / Oxford vaccine

AstraZeneca and the University of Oxford today recognized a manufacturing error that is raising questions about the preliminary results and the effectiveness of their experimental vaccine against covid-19.

The statement, where the error is acknowledged, comes days after the company and the university described the vaccine as “highly effective”, not to mention why some participants in the 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 a lower dose appeared to be much more protected than 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 combined results, the manufacturers revealed that the vaccine appears to be 70% effective, but the way in which these were obtained raised questions by experts.

The partial results announced on Monday are the result of mass clinical trials underway 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 compared to others who received a vaccine against meningitis or a saline solution.

Before starting the trials, the researchers explained all the steps to follow and how to analyze the results. Any deviation from this protocol can jeopardize the results.

In a statement released on Wednesday, the University of Oxford said that some of the vials used in the test did not have the right concentration of vaccine, meaning that some volunteers received half a dose.

The university added that it discussed the problem with regulators and agreed to complete the test. The manufacturing problem was corrected, according to the statement.

For the 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 particularity.

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 stake is the fact that none of the participants in the low-dose group are older than 55, with younger people tending to have a stronger immune response than older people.

As a discussion is still the joining of the two participating groups that received different dosage levels to achieve an average effectiveness of 70%, pointed out one of the members of the global health program Chatham House, David Salisbury.

One of the Oxford scientists who leads the investigation believes that the greatest effectiveness in the group that took the reduced dose may be related to providing the exact amount of the vaccine to trigger the best immune response.

“Not too little, not too much. A lot can give a low quality answer too,” he said.

Details of clinical trial results will be published in medical journals and provided to regulators in the UK, who will decide on authorization for the vaccine to be marketed.

These reports will include a detailed analysis with demographic information or information about who became ill 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 resulting from more than 60 million cases of infection worldwide, according to a report made by the French agency AFP.

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