CARL O’DONNELL and MANAS MISHRA  JOHNSON & Johnson has announced that it would take at least a few days for an independent safety panel to evaluate an unexplained illness of a study participant that led to a pause in the company's COVID-19 vaccine trial. J&J shares fell more than 2% following news of the pause and safety review. Rival AstraZeneca Plc's U.S. trial for its coronavirus vaccine candidate - which uses a similar technology - has remained on hold for more than a month after a participant in the company's UK trial fell ill. J&J, whose vaccine effort is among…