AstraZeneca may have used outdated data in its US vaccine trial results, giving an 'incomplete view' of how well the shot worked, officials said

• AstraZeneca may've included outdated data in its promising US vaccine trial results, officials said.
• An expert panel was "concerned" AstraZeneca may've given an "incomplete view of the efficacy data."
• AstraZeneca on Monday said its shot was 79% effective against preventing COVID-19 with symptoms.

AstraZeneca may have used partially outdated data when it reported promising US trial results on Monday, the US National Institute of Allergy and Infectious Diseases said in an unusual late-night statement.

AstraZeneca said Tuesday morning that it would publish updated data within 48 hours.

An independent expert panel that monitors trial safety was "concerned" that the information released by AstraZeneca was "outdated," which may have provided "an incomplete view of the efficacy data," the NIAID said late Monday night.

AstraZeneca earlier Monday said its COVID-19 vaccine was 79% effective against COVID-19 with symptoms and 100% effective at preventing severe illness and hospitalization in the late-stage US-based trial.

The results of this landmark trial of more than 32,000 people were initially viewed as having the potential to pave the way for US authorization and revive the shot's reputation in Europe, after more than 18 countries temporarily suspended the shot while regulators investigated potential side effects.

Read more: COVID Vaccine Tracker: AstraZeneca's shot proves safe and effective and is headed to the FDA

The NIAID said AstraZeneca should work with the panel of experts, called the Data and Safety Monitoring Board, "to review the efficacy data and ensure the most accurate, up-to-date efficacy data is made public as quickly as possible."

AstraZeneca said in a statement Tuesday morning that it would immediately engage with the panel and share the most up-to-date efficacy data within 48 hours.

"The numbers published yesterday were based on a pre-specified interim analysis with a data cut-off of 17 February," the company said.

"We have reviewed the preliminary assessment of the primary analysis and the results were consistent with the interim analysis. We are now completing the validation of the statistical analysis.

"We will immediately engage with the independent data safety monitoring board (DSMB) to share our primary analysis with the most up to date efficacy data. We intend to issue results of the primary analysis within 48 hours."

The NIAID is headed by Dr. Anthony Fauci, President Joe Biden's chief medical advisor, and is part of the National Institute of Health. The Data and Safety Monitoring Board reports into the NIH.

Fauci told STAT on Tuesday that the NIAID released the statement so it would not be accused of "covering something up." "It was an unforced error by the company," he said.

Fauci told "Good Morning America" on Tuesday that AstraZeneca's vaccine was likely to be "very good."

"If you look at it, the data really are quite good, but when they put it into the press release, it wasn't completely accurate," he said.

Fauci said that the Food and Drug Administration, when it reviews AstraZeneca's vaccine data ahead of its US authorization, would make an independent decision about the vaccine's effectiveness.

Regarding the muddled announcement of the trial results, Dr. Eric Topol, a clinical-trials expert at Scripps Research Translational Institute in San Diego, told The New York Times that he had "never seen anything like this."