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Objective: Most vaccines provide indirect community protection by preventing the transmission of the disease. Paradoxically, this effect can also motivate omission of vaccination because increasing vaccination rates reduce the risk of infection and, therefore, the individual benefit of vaccination. Consequently, vaccination becomes a social dilemma where individuals’ interests conflict with group interests. The current study investigated two social nudge interventions aiming to increasing individuals’ motivation to act in the group’s interest. Rewarding the attainment of the goal (disease elimination) is hypothesized to increase goal-directed behavior (vaccination). Further, it is assumed that comparisons with another group increase cooperative vaccination within one’s own group. Method: In a laboratory experiment, the interactive vaccination (I-Vax) game was used to model the direct and indirect effects of vaccinations. The game was played by 288 participants over 20 rounds. The experimental setup varied the feedback information after each round to implement a 2 (rewarding goal-attainment: present vs. absent) × 2 (intergroup comparison: present vs. absent) between-subjects design. Results: Analyses revealed the expected positive effect of rewarding goal-attainment, which was particularly strong at the beginning and weakened over the course of repeated decisions. The effect of intergroup comparisons was also positive but did not reach conventional criteria of statistical significance. Conclusions: The current experiment shows that communicating and rewarding “small wins” may increase individuals’ willingness to act in the group’s interest. Intergroup processes deserve further attention and investigation as potential strategies for improving vaccine communication and advocacy.