This dissertation examines how message framing and social norm cues shape participants’ responses to COVID-19 booster vaccination messages in China, with particular attention to the role of collectivist orientation. Guided by framing theory and social norm theory, a 2 x 3 factorial experiment was conducted in which participants were randomly assigned to messages that varied in framing (emphasizing the gains or losses to others) and social norm type (injunctive, descriptive, or no norm). The study assessed attitudes toward the COVID-19 booster vaccine, intention to receive the booster, and several related behaviors, including recommending vaccination to others, sharing vaccine information, and accompanying loved ones to receive the booster. The results showed clear differences in how message strategies influenced behavioral intentions. Loss-framed messages that emphasized potential harm to others were more effective than gain-framed messages in increasing intentions to receive and recommend the COVID-19 booster. Injunctive norm messages highlighting social approval also produced higher vaccination intentions than descriptive or norm messages, whereas descriptive norm messages did not differ significantly from messages without normative cues. In contrast, neither message framing nor social norm cues significantly influenced attitude toward the booster vaccine, suggesting that these message strategies primarily affected motivation to act rather than evaluations of the vaccine itself. No significant interaction was found between framing and social norm type, indicating that their effects operated independently. Further analyses revealed that collectivist orientation played an important role in shaping message effectiveness. Individuals with stronger collectivist orientation reported higher booster intentions overall and were more responsive to social norm messages, regardless of norm type. However, collectivist orientation did not moderate the effect of message framing. Together, these findings show that other-focused loss framing and injunctive norm cues are especially effective for promoting COVID-19 booster uptake in collectivist context. By distinguishing between message effects on attitudes and behavioral intentions and highlighting the moderating role of cultural orientation, this study contributes to framing theory, social norm theory, and cross-cultural health communication. The results also offer practical guidance for designing culturally sensitive public health messages to promote booster vaccination and similar preventive health behaviors.