AstraZeneca Reveals Dosing Error in Coronavirus Vaccine Trials

The high efficacy of the AstraZeneca and Oxford University coronavirus vaccine may be due in part to a dosing error.

In the vaccine efficacy press release published Monday, the vaccine candidate was more effective – up to 90% – in the group that received a half dose and then a full dose.

But the candidate vaccine was only 62% effective in the group that received two full doses.

Mene Pangalos, head of biopharmaceutical research and development at AstraZeneca, admitted to Reuters on Monday that some participants received a half dose and then a full dose due to a dosing error.

Pangalos called it a “useful mistake” in a subsequent interview with the New York Times, published Wednesday.

The University of Oxford said in a statement Wednesday that some of the trial vials did not contain the correct concentration of the vaccine. The university said the issue was discussed with regulators and they decided to complete the late-stage trial in two groups, according to the AP.

Experts say that the small number of people in the low-dose group – about 2,741 – makes it difficult to know whether efficacy is a statistical rarity.

Also, none of the people in the low-dose group were over 55 years old, and younger people tend to have stronger immune responses than older people.

A spokesperson for the University of Oxford told Euronews that “as a result of a difference in the manufacturing process” the phase I test method “was shown to overestimate the dose in new lots of the vaccine, resulting in the administration of half dose of the vaccine as the first dose. “

After discussion with the regulator, the two different concentrations were tested in the phase III trials.

David Salisbury, an associate member of the Chatham House global health program, said another area of ​​confusion is that the press release combined the results of the two groups to achieve an average of 70% effectiveness.

“You’ve taken two studies that used different dosages and you’ve come up with a compound that doesn’t represent either dose,” Salisbury told the AP. “I think a lot of people have a problem with that.”

The researchers say that a smaller first dose may be more effective because just the right amount is needed to elicit a good immune response.

“Astrazeneca / Oxford score poorly on transparency and rigor in terms of the vaccine trial results they have reported. This is not like at Pfizer or Moderna, where we had the protocols up front and a prespecified primary analysis was reported. “Natalie Dean, associate professor of biostatistics at the University of Florida.

“If they’re looking to get the half dose approved, they have to wait until they have a convincing result. Otherwise, we may land in ‘evidence limbo.’

More detailed trial results are expected to be provided to regulators who will decide whether to license the vaccine.

Moncef Slaoui, who heads the U.S. coronavirus vaccine program, said in a call to reporters that the country’s authorities are trying to determine what immune response the vaccine produced.

They may decide to modify the AstraZeneca study in the US to include half doses: “But we want it to be based on data and science,” he said.

Euronews has contacted AstraZeneca for their comments.