AstraZeneca Covid-19 vaccine study put on hold due to suspected adverse reaction
> It was not immediately clear who placed the hold on the trial, though it is possible it was placed voluntarily by AstraZeneca and not ordered by any regulatory agency. The nature of the adverse reaction and when it happened were also not immediately known, though the participant is expected to recover, according to an individual familiar with the matter.<p>What would be a reason why they don't disclose this detail  immediately but only to tell public the trial is on hold?