The Data and Safety Monitoring Board, charged with ensuring the safety and accuracy of AstraZeneca’s vaccine trial, has expressed concerns to the National Institute for Allergy and Infectious Diseases that the information released about the testing results included outdated information.

This “may have provided an incomplete view of the efficacy data,” the agency said in a statement early Tuesday, without elaborating.

“We urge the company to work with the DSMB to review the efficacy data and ensure the most accurate, up-to-date efficacy data be made public as quickly as possible,” said the group headed by Anthony Fauci, the top U.S. infectious disease official.

AstraZeneca did not immediately respond to a request for comment made outside of office hours.

The company’s shares traded 1.3% lower early Tuesday in London.

The DSMB, an independent panel, also raised its concerns to the British drugmaker and to the Biomedical Advanced Research and Development Authority, a U.S. agency that partially funded the shot’s development.

The disclosure is another setback for AstraZeneca, which earlier Monday said its vaccine was found 79% effective in preventing Covid-19 in a U.S. clinical trial of more than 30,000 volunteers. After being cleared for use in the U.K. and many other nations, the company is preparing to seek approval from the U.S. Food and Drug Administration. That greenlight is now likely to be delayed after the monitoring board’s concerns.

Efficacy Rates

The efficacy rate in the U.S. trial was stronger than the 70% figure AstraZeneca reported from an earlier study. But those data were an average of different readings — 62% and 90% — from two arms of the trial. Because of a manufacturing error, one group of participants had received a lower first dose, which produced the higher reading, compared with those getting two standard doses. Further analysis suggested it was the greater dosing gap rather than amount that had created the difference.

AstraZeneca’s vaccine, developed with Oxford University, was once seen as a frontrunner to protect the world against Covid-19 but has been beset by a series of complications. It’s now at the center of a supply showdown with the European Union just days after concerns about blood clots prompted a dozen member states to suspend immunizations.

“The last thing this vaccine needs is more concern when we kind of thought we were at that point now where we’d put to bed all the other concerns, and then a new one pops up the same day,” said Paul Griffin, an associate professor of medicine at the University of Queensland in Brisbane, who is conducting clinical studies in Australia on four Covid-19 vaccine candidates.

“It was referring to outdated information, and it’s kind of hard to imagine how outdated information could be included when these vaccines are all fairly new,” said Griffin, who is an infectious-disease physician and microbiologist. “The impression I got was that it seemed to be something very significant they were alluding to.”