Analysis of Japanese Twitter Posts Related to COVID-19 Vaccination Focusing on Frequently Occurring Words and Emotional Expressions

The Coronavirus Disease 2019 (COVID-19) pandemic and its prolonged effects have been widely discussed on social media, and these discussions have been analyzed in various studies. A long-term analysis of Twitter (now “X”) posts regarding COVID-19 vaccination is essential for informing policy and improving public health communication strategies. In addition, to prevent the spread of infectious diseases, it is crucial to rapidly promote vaccination while mitigating the impact of negative sentiment toward vaccination on social media platforms. Therefore, identifying the key factors behind negative discussions is important for guiding policy decisions and shaping responses. In this study, we collected Japanese tweets (posts) containing the words “Corona” and “vaccine” that were posted from February 2021 to December 2022. The results indicate that negative sentiment was primarily driven by concerns about adverse reactions and general fear and anxiety, which were particularly prominent before vaccination for the general public began, as well as mentions of pain during and after vaccination. While concerns about adverse reactions persisted throughout the analysis period, their prominence decreased over time as positive reactions became more frequent. Our findings provide insights into the characteristics and key factors behind negative discussions on COVID-19 vaccination in the Japanese context and may help improve public health communication strategies.