The passive surveillance system is an important tool in pharmacovigilance of vaccines. However, reporting of adverse events following immunization (AEFI) post-marketing has limitations regarding under-reporting, biased reports and lack of exposure data resulting in imprecise estimates. New mobile application technology may provide an opportunity for an enhanced surveillance. A pre-requisite for the use of new app-based technology is to identify practical challenges and end users' preferences for design of app-features. The objectives were (i) to investigate the recruitment and feasibility of an app-based study in Germany, (ii) to assess individuals' motivation to participate in such a study and (iii) to identify app-features for reporting AEFI. We conducted a cross-sectional study among employees of a financial institution who attended the occupational health office during the seasonal influenza vaccination in November 2017. Participants tested feasibility and assessed an app prototype for AEFI reporting by using a case vignette and a questionnaire. Of the 153 attending employees, 65 (42%) agreed to participate and returned the questionnaire. Twenty-three (63%) rated the experience of reporting AEFI with the app prototype to be positive. Among three features offered for gamification, collecting points was most frequently chosen (n=22, 34%). The main reason for declining participation was the apprehension about data protection (n=28, 43%). Results suggest that the app-based technology was well accepted and is a suitable supplement for AEFI reporting and in our study. A convincing data protection concept is likely to enhance acceptability of such a system.