自新冠肺炎發生後，國際環境出現大幅度變化，期間中國國家主席習近平提出「東昇西降」的説法，認為美國霸權終漸衰敗。有鑑於此，本研究將探討中美援外政策，並以疫苗外交為案例，檢證中美關係之強弱變化。中、美各自運用疫苗外交，凝聚盟友鞏固團結意識。中國先輸送口罩及防護衣等物資捐助，並採取醫療資訊交換、線上視訊會議等行動實踐衛生外交，國產疫苗出現後，中國更積極投入疫苗外交。中國疫苗外交的投射對象，以《一帶一路倡議》沿線國家為主，重新刺激因疫情而停擺的合作機制外，更為挽回中國的國際聲譽，意圖結伴共敵美國「民主同盟圈」。美國參加四方會談、G7峰會、北約峰會等國際會議將捐贈疫苗於COVAX，並因應各國緊急需求做針對性投射。同時，美國疫苗具高保護力，能夠降低罹患重症機率，深獲各國信賴。更重要地是，美國選擇此時加入疫苗外交，是爲降低中國疫苗外交的影響力。研究結果顯示中、美看似衝突氣氛一觸即發，但由於疫苗外交的軟性力量與公共價值，發現雙方並未因各自疫苗外交加劇彼此競爭意識外，「東昇西降」論點較難成立。假若未來中美間若能在摒除意識形態競爭，增強疫苗技術合作，以全人類生命安全為使命，或許可以為中美化解衝突，尋求和平道路。

After the outbreak of COVID-19, Xi Jinping, the President of the People's Republic of China, proposed the concept of the rise of the East and the decline of the West, and scholars in China also considered it an unavoidable trend in the future, predicting that the hegemony of the Unite States (US) will eventually decline. Thus, this study explored the foreign aid policy and used vaccine diplomacy as an example to verify the changes in the power relations between the two countries. The research results showed that despite the tense atmosphere between China and the US that seemed as if war would breakout at any moment, because of the soft power and public value of vaccine diplomacy, neither country exacerbated its competitiveness because of its individual vaccine diplomacy. Consequently, the idea of the rise of the East and the decline of the West did not stand. If in the future, the two countries can get rid of ideological competition, seek cooperation in vaccine technologies, and consider maintaining the safety of all humans as their shared mission, conflicts between China and the US may be resolved, and a path to peace may be paved.