search

AstraZeneca facing questions about vaccine after admitting to testing error

Manufacturing glitch casts shadow on results of study after British drug group and Oxford university said lower dose of inoculation provides better protection from virus

A researcher in a laboratory at the Jenner Institute in Oxford, England, works on the coronavirus vaccine developed by AstraZeneca and Oxford University, November 23, 2020. (University of Oxford/John Cairns via AP, File)
A researcher in a laboratory at the Jenner Institute in Oxford, England, works on the coronavirus vaccine developed by AstraZeneca and Oxford University, November 23, 2020. (University of Oxford/John Cairns via AP, File)

AstraZeneca and the University of Oxford on Wednesday acknowledged a manufacturing error that is raising questions about preliminary results of their experimental COVID-19 vaccine.

A statement describing the error came days after the company and the university described the shots as “highly effective” and made no mention of why some study participants didn’t receive as much vaccine in the first of two shots as expected.

In a surprise, the group of volunteers that got a lower dose seemed to be much better protected than the volunteers who got two full doses. In the low-dose group, AstraZeneca said, the vaccine appeared to be 90% effective. In the group that got two full doses, the vaccine appeared to be 62% effective. Combined, the drug makers said the vaccine appeared to be 70% effective. But the way in which the results were arrived at and reported by the companies has led to pointed questions from experts.

The partial results announced Monday are from large ongoing studies in the UK and Brazil designed to determine the optimal dose of vaccine, as well as examine safety and effectiveness. Multiple combinations and doses were tried in the volunteers. They were compared to others who were given a meningitis vaccine or a saline shot.

Before they begin their research, scientists spell out all the steps they are taking, and how they will analyze the results. Any deviation from that protocol can put the results in question.

But in a statement Wednesday, Oxford University said some of the vials used in the trial didn’t have the right concentration of vaccine so some volunteers got a half dose. The university said that it discussed the problem with regulators, and agreed to complete the late stage trial with two groups. The manufacturing problem has been corrected, according to the statement.

An illustration picture shows vials with COVID-19 Vaccine stickers attached and syringes with the logo of British pharmaceutical company AstraZeneca on November 17, 2020. (JUSTIN TALLIS/AFP)

Experts say the relatively small number of people in the low dose group makes it difficult to know if the effectiveness seen in the group is real or a statistical quirk. 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.

Additionally, none of the people in the low-dose group were over 55 years old. Younger people tend to mount a stronger immune response than older people, so it could be that the youth of the participants in the low-dose group is why it looked more effective, not the size of the dose.

Another point of confusion comes from a decision to pool results from two groups of participants who received different dosing levels to reach an average 70% effectiveness, said David Salisbury, and associate fellow of the global health program at the Chatham House think tank.

“You’ve taken two studies for which different doses were used and come up with a composite that doesn’t represent either of the doses,″ he said of the figure. “I think many people are having trouble with that.″

At this stage, Oxford researchers say they aren’t certain why a smaller dose would be more effective and they are working to uncover the reason.

Sarah Gilbert, one of the Oxford scientists leading the research, said the answer is probably related to providing exactly the right amount of vaccine to trigger the best immune response.

“It’s the Goldilocks amount that you want, I think, not too little and not too much. Too much could give you a poor quality response as well,’’ she said. “So you want just the right amount and it’s a bit hit and miss when you’re trying to go quickly to get that perfect first time.”

Details of the trial results will be published in medical journals and provided to UK regulators so they can decide whether to authorize distribution of the vaccine. Those reports will include a detailed breakdown that includes demographic and other information about who got sick in each group, and give a more complete picture of how effective the vaccine is.

Laboratory technicians work at the mAbxience biopharmaceutical company on an experimental coronavirus vaccine developed by Oxford University and the laboratory AstraZeneca in Garin, Argentina, August 14, 2020. (Natacha Pisarenko/AP)

Moncef Slaoui, who leads the US coronavirus vaccine program Operation Warp Speed, said Tuesday in a call with reporters that US officials were trying to determine what immune response the vaccine produced, and may decide to modify the AstraZeneca study in the US to include a half dose.

“But we want it to be based on data and science,” he said.

Days before the initial announcement on the results of the trials, Prime Minister Benjamin Netanyahu announced that Israel was close to signing a deal with AstraZeneca to purchase “millions” of doses of its vaccine.

If signed, it would be the third deal signed by Israel to receive vaccinations, following similar deals with Pfizer and Moderna. Israel has also been in talks with Russia to receive its Sputnik V vaccine, though some experts have questioned its opaque certification process.

However, none of the deals guarantees a deadline for the arrival of the vaccines, and with mass global demand, it is still not clear how many doses Israel will get, and when.

Israel has also been working on a homegrown vaccine, though it is currently only in phase 1 trials and its development is expected to take months longer than the foreign candidates. Channel 12 reported Friday that it will likely be available to the public this summer.

read more:
comments