BACKGROUND Unlike past pandemics, COVID-19 is different to the extent that there is an unprecedented surge in both peer-reviewed and preprint research publications, and important scientific conversations about it are rampant on online social network, even among lay people. Clearly, this new phenomenon of scientific discourse is not well understood in that we do not know the diffusion patterns of peer-reviewed publications vis-à-vis preprints and what makes them viral. OBJECTIVE To inform health science communicator and policy makers’ decision on how to promote reliable sharing of crucial pandemic science on social media, this paper aims to examine how the emotionality of the messages about preprint and peer-reviewed publications shape their diffusion through online social networks. METHODS We collected a large sample of all Twitter discussion of early month COVID-19 medical research outputs in both preprint servers and peer-reviewed journals and conducted statistical analyses to examine how the emotional valence, specific emotion, as well as scientists’ participation influence the retweet rate. RESULTS Our large-scale analyses (n=243,567) revealed that scientific publications with positive emotion tweets were transmitted faster than those with negative emotion tweets, especially for messages about preprints. Our results also showed that scientists’ participation on social media could accentuate the positive emotion effects on the sharing of peer-reviewed publications. CONCLUSIONS Clear communication of critical science is crucial in the nascent stage of a pandemic. Through revealing the emotional dynamics in the social media sharing of COVID-19 scientific outputs, our study offers scientists and policy makers an avenue to shape the discussion and diffusion of emerging scientific publications by manipulating the emotionality of the tweets.

Background Unlike past pandemics, COVID-19 is different to the extent that there is an unprecedented surge in both peer-reviewed and preprint research publications, and important scientific conversations about it are rampant on online social networks, even among laypeople. Clearly, this new phenomenon of scientific discourse is not well understood in that we do not know the diffusion patterns of peer-reviewed publications vis-à-vis preprints and what makes them viral. Objective This paper aimed to examine how the emotionality of messages about preprint and peer-reviewed publications shapes their diffusion through online social networks in order to inform health science communicators’ and policy makers’ decisions on how to promote reliable sharing of crucial pandemic science on social media. Methods We collected a large sample of Twitter discussions of early (January to May 2020) COVID-19 medical research outputs, which were tracked by Altmetric, in both preprint servers and peer-reviewed journals, and conducted statistical analyses to examine emotional valence, specific emotions, and the role of scientists as content creators in influencing the retweet rate. Results Our large-scale analyses (n=243,567) revealed that scientific publication tweets with positive emotions were transmitted faster than those with negative emotions, especially for messages about preprints. Our results also showed that scientists’ participation in social media as content creators could accentuate the positive emotion effects on the sharing of peer-reviewed publications. Conclusions Clear communication of critical science is crucial in the nascent stage of a pandemic. By revealing the emotional dynamics in the social media sharing of COVID-19 scientific outputs, our study offers scientists and policy makers an avenue to shape the discussion and diffusion of emerging scientific publications through manipulation of the emotionality of tweets. Scientists could use emotional language to promote the diffusion of more reliable peer-reviewed articles, while avoiding using too much positive emotional language in social media messages about preprints if they think that it is too early to widely communicate the preprint (not peer reviewed) data to the public.