a.) If it is your data, there is no ethical issue.
b.) If it is your institute data, it is not your data.
c.) Even if it is somebody's else data, but has been published, you can use it by giving credit to the owners. If you want to be polite and want to improve the reliability of your analysis, offer collaboration to the data owners. Data owners always know way more about their data than the pure number or information written.
d.) If you want to use data from other source than a peer reviewed paper, the best thing is asking permission.
a.) If it is your data, there is no ethical issue.
b.) If it is your institute data, it is not your data.
c.) Even if it is somebody's else data, but has been published, you can use it by giving credit to the owners. If you want to be polite and want to improve the reliability of your analysis, offer collaboration to the data owners. Data owners always know way more about their data than the pure number or information written.
d.) If you want to use data from other source than a peer reviewed paper, the best thing is asking permission.
Check the informed consent for the primary trial. Stipulations for future use of data should guide you. Seeking the guidance of the IRB is always advisable and attribution if applicable is a must.
It depends where you obtained the secondary data. If you obtained in the organisation eg minutes, reports etc then you need such approval. If however it is available on the public domain there is no such need. Take an example of company documents on their website. That data is already available on the public domain. The only thing you need to do is to reference and show that you obtained it from such website but no need to get approval to access it for research purposes. They put it on there knowing that it will be accessed by members of the public.
It dependes very much whether the study was a clinical trial thus performed under ICH-GCP conditions or not.
Clinical trials according ICH-GCP should state in the protocol on secondary objectives and endpoints that we'll be reported in the Statistical Analysis Plan that MUST be finalized before databse is locked and analyzed.
If in this case you wish to perform a secondary analysis you should inform the EC with a brief note and amend the protocol.
If your secondary analysis is indeed a "post hoc" analysis (i.e. outcome by gender, or by age, or by ethnic group) you may not inform the EC but report the results in the Clinical Study Report.
All other cases are less stringent than the example I reported here. I would however suggest to report to EC the results of the additional secondary analysis in the form requested by the the institution.