Assessing the Interplay Between Public Attention and Government Responsiveness With Digital Trace Data: Navigating Leadership and Followership in China's COVID-19 Vaccination Campaign

China's digital campaign to "vaccinate all who can be vaccinated," officially launched in December 2020, carries global implications. Grounded in the agenda-setting framework to reveal how the responses of different groups are shaped and their agendas interact, this study analyzed two years of Sina Weibo (the largest Chinese microblogging service) and Baidu (the leading search engine in China) search index data to investigate the interrelationships among different groups' issue foci and the effects of sentiment, rationality, and moral motivation in the agenda-setting process. Large-scale computational analyses were conducted to determine the extent to which the Chinese government followed the public's issue preferences and identify which segment of the public had a stronger ability to set the agenda. The results indicated that as the central government transitioned from leading to following the public, regional governments had a greater impact on the public agenda compared to the central government or media. The government, public, and media differed in their usage of sentiment and moral motivation on social media during the vaccination campaign, and this varied depending on the campaign's stage. Notably, all stakeholders emphasized individual-centered values over community-centered values when addressing vaccination. The findings shed light on effective strategies for social mobilization through targeted public health messaging.