"I just can't figure out where all of the information is coming from and how it's being combined," said Natalie Dean, biostatistician and expert on vaccine study design at the University of Florida. She wrote on Twitter that AstraZeneca and Oxford "get poor marks for transparency and accuracy when it comes to the results of the vaccine studies they have reported".
As AstraZeneca's shares fell on Monday, executives at the company held several private conference calls with industry analysts disclosing details not included in the public announcement, including how the Covid-19 cases were broken down into different groups. Such disclosures to analysts are not uncommon in the industry, but often lead to criticism of why the details were not made available to the public.
Bigger problems soon arose.
Mr Pangalos told Reuters on Monday that the company did not intend for participants to receive half the dose. British researchers doing the study there had intended to give volunteers the full dose initially, but one misjudgment meant they were mistakenly given half a dose. Mr. Pangalos described the bug as "coincidental," which allowed researchers to come across a more promising dosage regimen.
For many outside experts, this undermined the credibility of the results as the tightly calibrated clinical trials were not designed to test how well a starting half-strength dose worked.
The company's initial announcement made no mention of the random nature of the discovery.
"The reality is that it could be a pretty useful mistake," Pangalos said in an interview with the New York Times on Wednesday. "It didn't put anyone at risk. It was a dosing error. Everyone was moving very quickly. We corrected the error and continued the study without making any changes to the study, and we agreed with the regulatory agency to include these patients in the analysis of the study . "
He added, “What is there to reveal? It doesn't really matter whether it was done on purpose or not. "
In the statement attributed to Oxford, Ms. Meixell, the spokeswoman for AstraZeneca, said the error was due to a problem that has since been fixed in how some of the vaccine doses were made.