Under what condition can deviations from the trial protocol occur without prior IRB approval?

Deviations from the trial protocol without prior Institutional Review Board (IRB) approval should not occur under any circumstances, as this could compromise the integrity of the study and jeopardize participant safety. The IRB's role is to protect the rights and welfare of research subjects, and any changes to the protocol need to be carefully assessed by this committee to ensure that they do not introduce undue risk or alter the study's design inappropriately.

The other choices suggest conditions under which deviations might be permissible, but they overlook the fundamental principle that all aspects of a clinical trial must adhere to the approved protocol. Changes made without IRB approval could lead to ethical concerns, increase potential risks to participants, and invalidate the study's results. Hence, maintaining strict adherence to the protocol and seeking IRB approval for any necessary deviations is essential for compliance with regulatory standards and ethical guidelines in clinical research.