Guidelines 03/2020 on the processing of data concerning health for the purpose of scientific research in the context of the COVID-19 outbreak

Subparagraph 5.1.2.2  Disproportionate effort

37. In determining what constitutes disproportionate effort, Recital 62 refers to the number of data subjects, the age of the data and appropriate safeguards in place as possible indicative factors. In the Transparency Guidelines mentioned above, it is recommended that the controller should therefore carry out a balancing exercise to assess the effort involved to provide the information to data subjects against the impact and effects on the data subject if they are not provided with the information.

38. Example:  A large number of data subjects where there is no available contact information could be considered as a disproportionate effort to provide the information.