The FDA body will assess data from earlier trials of similar coronavirus vaccines developed by the same scientists, three sources familiar with the details told Reuters.
AstraZeneca’s Covid-19 vaccine trials in the US has been on hold since September 6 after a study participant in Britain fell ill with what was believed to be a rare spinal inflammatory disorder called transverse myelitis.
The widened scope of the FDA probe raises the likelihood of additional delays for what has been one of the most advanced Covid-19 vaccine candidates in development.
The requested data was expected to arrive this week, after which the FDA would need time to analyze it, two of the sources said.
Effective vaccines are seen as essential to help end a pandemic that has killed more than one million people worldwide.
The administration of President Donald Trump has pledged $1.2 billion to support the development of AstraZeneca's Covid-19 vaccine and secure 300 million doses for the United States.
Other leading companies in the US vaccine race include Pfizer Inc, Moderna Inc and Johnson & Johnson.