Background: During the COVID-19 pandemic, growth in citizen engagement with social media platforms has enabled public health departments to accelerate and improve health information dissemination, developing transparency and trust between governments and citizens. In light of these benefits, it is imperative to learn the antecedents and underlying mechanisms for this to maintain and enhance engagement. Objective: The aim of this study is to determine the factors and influencing mechanisms related to citizen engagement with the TikTok account of the National Health Commission of China during the COVID-19 pandemic. Methods: Using a web crawler, 355 short videos were collected from the Healthy China account on TikTok (with more than 3 million followers throughout China), covering the period from January 21, 2020, to April 25, 2020. The title and video length, as well as the number of likes, shares, and comments were collected for each video. After classifying them using content analysis, a series of negative binomial regression analyses were completed. Results: Among the 355 videos, 154 (43.4%) related to guidance for clinicians, patients, and ordinary citizens, followed by information concerning the government’s handling of the pandemic (n=100, 28.2%), the latest news about COVID-19 (n=61, 17.2%), and appreciation toward frontline emergency services (n=40, 11.3%). Video length, titles, dialogic loop, and content type all influenced the level of citizen engagement. Specifically, video length was negatively associated with the number of likes (incidence rate ratio [IRR]=0.19, P<.001) and comments (IRR=0.39, P<.001). Title length was positively related to the number of shares (IRR=24.25, P=.01), likes (IRR=8.50, P=.03), and comments (IRR=7.85, P=.02). Dialogic loop negatively predicted the number of shares (IRR=0.56, P=.03). In comparison to appreciative information, information about the government’s handling of the situation (IRR=5.16, P<.001) and guidelines information (IRR=7.31, P<.001) were positively correlated with the number of shares, while the latest news was negatively related to the number of likes received (IRR=0.46, P=.004). More importantly, the relationship between predictors and citizen engagement was moderated by the emotional valence of video titles. Longer videos with positive titles received a higher number of likes (IRR=21.72, P=.04) and comments (IRR=10.14, P=.047). Furthermore, for short videos related to government handling of the pandemic (IRR=14.48, P=.04) and guidance for stakeholders (IRR=7.59, P=.04), positive titles received a greater number of shares. Videos related to the latest news (IRR=66.69, P=.04) received more likes if the video title displayed higher levels of positive emotion. Conclusions: During the COVID-19 pandemic, videos were frequently published on government social media platforms. Video length, title, dialogic loop, and content type significantly influenced the level of citizen engagement. These relationships were moderated by the emotional valence of the video’s title. Our findings have implications for maintaining and enhancing citizen engagement via government social media.

Flashbulb memory (FBM) is viewed as a special type of autobiographical memory due to its richness of individuals’ self-related details when hearing the news and the long duration. It also helps shape people’s impression of public events to some extent. Given that personal involvement is one of the important antecedent variables of FBM, this study proposed to investigate it from spatiotemporal involvement (spatiotemporal distance) and empathic involvement (empathy level) to explore the impact of personal involvement on the formation of FBM during the Covid-19 pandemic. In particular, digital media dependency was considered in the influence of involvement on the FBM since it is a crucial information source for individuals and a path to spread information about their lives and work during the pandemic. In this study, a total of 546 valid questionnaires (from May 1, 2022, to May 7, 2022) and 349 valid questionnaires (from May 10, 2022, to May 17, 2022) were collected through a two-stage online survey in Shanghai, China towards the epidemic wave at the end of March 2022. The mediating mode of digital media dependency was also examined on personal involvement in FBM performance, which consists of FBM specificity, confidence, and consistency. Results showed that empathic involvement had a significant negative influence on FBM specificity, namely the higher the empathy level was, the worse the FBM specificity would be, in which digital media dependency played a suppressing effect. Individuals’ spatiotemporal involvement was proved to have a significant positive influence on FBM specificity and consistency. It was one of the first to investigate the FBM formation process around “small peak” events in the context of the ongoing pandemic. Innovatively, empathy was adopted as the index of memory arousal for empathic involvement, and digital media dependency was considered an important mediator variable in the memory study. The research results have practical significance for promoting the process of epidemic recovery integrated with digital media and can provide a social reference for the shaping process of disaster memory from the perspective of digital information and emotional transmission.