RESUMO
BackgroundThe pandemic of COVID-19 is causing a crisis in public health, food systems, and employment. Vaccination is considered as one of the most effective ways for containing the pandemic, but widespread vaccine hesitation on social media may curtail uptake progress. Fully comprehending public sentiment towards the COVID-19 vaccine is critical to building confidence on the vaccines and achieving herd immunity, especially in Japan with inadequate vaccine confidence. ObjectiveThis study aims to explore the opinion and sentiment towards the COVID-19 vaccine in Japanese tweets, before and at the beginning of large-scale vaccinations. MethodsWe collected 144,101 Japanese tweets containing COVID-19 vaccine-related keywords between August 1, 2020, and June 30, 2021. We visualized the trend of number of tweets and identified the critical events that triggered a surge and provided high-frequency unigram and bigram tokens. Also, we performed sentiment analysis and calculated the correlation of number of tweets and positive/negative sentiments with infection, death, and vaccinated cases. we also used the latent Dirichlet allocation (LDA) model to identify topics of tweets. In addition, we conducted analysis on three vaccine brands (Pfizer/Moderna/AstraZeneca). ResultsDaily number of tweets continued growing and the growth accelerated since the large-scale vaccinations in Japan. The sentiment of around 85% tweets were neutral, and the negative sentiment overwhelmed the positive sentiment in the other tweets. Number of tweets strongly correlated (r[≥]0.5) with infection/death/vaccinated cases, and the number of negative tweets correlated strongly with the number of infection/death cases but weakened after the first vaccination in Japan. LDA identified three public-concerned topics: vaccine appointment and distribution strategy; Different vaccines development progress and approval status of countries; Side effects and effectiveness against mutated viruses. Among vaccines of the three manufactures, Pfizer won the most attention and Moderna the least. ConclusionsOur findings indicated that negative sentiment towards vaccines dominated than positive sentiment in Japan. Changes in number of tweets and sentiments might be driven by critical events related to the COVID-19 vaccine, and negative sentiment continued increasing when numerous adverse accidents occurred at the beginning of large-scale vaccinations. Under the negative sentiment, the concerns of three vaccine brands remains effectiveness and safety with slight differences. The policymakers should provide more evidence about the effectiveness and safety of vaccines and optimize the process of vaccinations.
