Which consideration supported the IRB's conclusion that the research did not involve human subjects?

The consideration that supports the IRB's conclusion that the research did not involve human subjects centers around the absence of interaction or intervention with individuals and the fact that the data lacks identifiers. When conducting research that requires human subjects, one of the primary concerns is the potential for direct interaction with those individuals and the confidentiality of their information. If the researcher is not engaging directly with subjects and is working with data that has been stripped of any personal identifiers, then the risk of harm or breach of privacy is significantly reduced. This is a key factor in determining whether a study qualifies as involving human subjects under federal regulations.

While the data being collected originally for surveillance purposes (as indicated in one of the other choices) may also play a role in supporting the decision, it is the specific mention of no interaction or intervention, combined with the absence of identifiers, that clearly delineates the study from those that involve human subjects. Other choices such as the affiliation of the CDC as a federal agency or the time frame of the data collection do not directly impact the determination of whether human subjects are involved in the research. These factors may provide context but do not address the critical elements of subject interaction or data anonymization that are at the core of the IRB's evaluation.