Evolution of social mood in Spain throughout the COVID-19 vaccination process. A machine learning approach to tweets analysis

Objectives: This paper presents a new approach based on the combination of machine learning techniques, in particular sentiment analysis using lexicons, and multivariate statistical methods to assess the evolution of social mood through the COVID-19 vaccination process in Spain. Methods: Analysing 41,669 Spanish tweets posted between 27-02-2020 and 31-12-2021, different sentiments were assessed using a list of Spanish words and their associations with eight basic emotions (anger, fear, anticipation, trust, surprise, sadness, joy and disgust) and three valences (neutral, negative and positive). How the different subjective emotions were distributed across the tweets was determined by using several descriptive statistics; a trajectory plot representing the emotional valence versus narrative time was also included. Results: The results achieved are highly illustrative of the social mood of citizens, registering the different emerging opinion clusters, gauging public states of mind via the collective valence, and detecting the prevalence of different emotions in the successive phases of the vaccination process. Conclusions: The present combination in formal models of objective and subjective information would therefore provide a more accurate vision of social reality, in this case regarding the COVID-19 vaccination process in Spain, which will enable a more effective resolution of problems