Introduction: Massive Open Online Courses (MOOCs) are an increasingly popular form of education in health professional education. VPs have been introduced in MOOCs to increase interactivity. There is a lack of research in understanding the reasons behind high dropout rates in MOOCs. We explored how learners interact with VPs and compared the significance of different VP designs on dropout rates. Methods: RCT of 378 participants split into two groups to interact with two VPs using different design: branching and linear. Data on node progression and VP attempts was analysed using descriptive and quantitative analysis. Results: Eight groups of learner interaction patterns were identified. The majority of learners completed the VP in a linear path in one attempt. A significant number either completed the case in a loop path in one attempt, completed in a linear path in multiple attempts or dropped out without attempting the case. VP design has a significant effect on dropout rates of learners. There is a higher dropout rate from a branched VP compared to linear VP. Discussion: Prior research showed that branched VPs are more engaging and promote greater learning compared to linear VPs. However, our results indicate that branched VPs had greater dropout compared to VPs that require less time to be solved. Conclusions: We conclude that branching had a negative effect on completion of the VP activity in the MOOC. Moreover, we believe that more complex VPs require more effort on task and this might not be a design that facilitates the interaction in a MOOC audience, where the participants might wish to acquire the basic medical knowledge offered by the course.