AstraZeneca Faces Difficult Questions About Its Vaccine After Admitting Mistake

“I just can’t figure out where all the information is coming from and how it’s combining together,” said Natalie Dean, a biostatistician and an expert in vaccine trial design at the University of Florida. She wrote on Twitter that AstraZeneca and Oxford “get a poor grade for transparency and rigor when it comes to the vaccine trial results they have reported.”

With AstraZeneca’s shares declining on Monday, company executives held several private conference calls with industry analysts in which they disclosed details that were not in the public announcement, including how the Covid-19 cases broke down across different groups. Such disclosures to analysts are not uncommon in the industry, but they often generate criticism about why the details were not shared with the public.

Bigger problems soon surfaced.

Mr. Pangalos told Reuters on Monday that the company had not intended for any participants to receive the half dose. British researchers running the trial there had meant to give the full dose initially to volunteers, but a miscalculation meant they were mistakenly given only a half dose. Mr. Pangalos described the error as “serendipity,” allowing researchers to stumble onto a more promising dosing regimen.

To many outside experts, that undercut the