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Between the ages of eighteen and twenty-five, young adults have to decide on their own for the first time whether or not they wish to get a DTP booster shot. Based on an experimental approach, this study—in which 303 young adults participated—tests the effectiveness of six different pro-DTP messages in terms of attitude change and behavioral intention change, using different message framing (gain versus loss) and arguments (getting vaccinated for the sake of one’s own health, to protect others, or to respect the law). The results show that, depending on the option, the message can have either a weak effectiveness or a negative effect by reducing the vaccination intention. Moreover, some message framings generate a sequential route that can be either affective or cognitive. Finally, the best option is to use a gain-framed message with a legal argument (“Get vaccinated to respect the law”).