Independent safety monitors will conduct their first review of the vaccine's safety and effectiveness after 75 trial subjects become infected with Covid-19, up from the original initial review plan after about 40 infections, according to a Reuters review of protocol documents issued in July and amended in mid-September.
The safety monitors could decide to stop the trial if the vaccine proves either highly effective, and therefore should be considered for public use before the trial concludes, or if serious safety problems appear.
"Safety is likely to have been a major reason" for the change, said Thomas Lumley, chair of biostatistics at the University of Auckland who was not involved with the study.
AstraZeneca would not say why it had made the change to its protocol.
(Writers: Marisa Taylor, Dan Levine, Nancy Lapid | Editors: Michele Gershberg, Bill Berkrot)
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