Vaccine Hesitancy on Social Media: Sentiment Analysis from June 2011 to April 2019.

Francisco Machío-Regidor,Juan Antonio Sicilia-Montalvo,Javier Bermejo-Higuera,Diego Piedrahita-Castillo,Hilary Piedrahita-Valdés,Javier Guillem-Saiz,Juan Ramón Bermejo-Higuera,Patricia Guillem-Saiz

doi:10.3390/vaccines9010028

Francisco Machío-Regidor, Juan Antonio Sicilia-Montalvo + Show 6 more

Open Access

https://doi.org/10.3390/vaccines9010028

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Abstract

Vaccine hesitancy was one of the ten major threats to global health in 2019, according to the World Health Organisation. Nowadays, social media has an important role in the spread of information, misinformation, and disinformation about vaccines. Monitoring vaccine-related conversations on social media could help us to identify the factors that contribute to vaccine confidence in each historical period and geographical area. We used a hybrid approach to perform an opinion-mining analysis on 1,499,227 vaccine-related tweets published on Twitter from 1st June 2011 to 30th April 2019. Our algorithm classified 69.36% of the tweets as neutral, 21.78% as positive, and 8.86% as negative. The percentage of neutral tweets showed a decreasing tendency, while the proportion of positive and negative tweets increased over time. Peaks in positive tweets were observed every April. The proportion of positive tweets was significantly higher in the middle of the week and decreased during weekends. Negative tweets followed the opposite pattern. Among users with ≥2 tweets, 91.83% had a homogeneous polarised discourse. Positive tweets were more prevalent in Switzerland (71.43%). Negative tweets were most common in the Netherlands (15.53%), Canada (11.32%), Japan (10.74%), and the United States (10.49%). Opinion mining is potentially useful to monitor online vaccine-related concerns and adapt vaccine promotion strategies accordingly.

Highlights

The Strategic Advisory Group of Experts (SAGE) Working Group on Vaccine Hesitancy defines vaccine hesitancy as the “delay in acceptance or refusal of vaccination despite the availability of vaccination services
Negative tweets never became predominant over neutral tweets, but they were more frequent than positive tweets on three periods: (1) Between July 2011 and March 2013 (+1.5% average), (2) December 2014 (+2.49%), (3) April 2016–June 2016 (+5.01% in May)
As for the relative frequency of tweets by day of the week, we found the same pattern described by Du J. et al [35]: the average rate of positive tweets was higher on Wednesdays and lower on weekends, while the average rate of negative tweets followed the opposite trend, and the neutral group remained without significant variations throughout the week

Summary

Introduction

The Strategic Advisory Group of Experts (SAGE) Working Group on Vaccine Hesitancy defines vaccine hesitancy as the “delay in acceptance or refusal of vaccination despite the availability of vaccination services. Vaccine hesitancy is complex and context-specific, varying across time, place, and vaccines. It is influenced by factors such as complacency, convenience, and confidence” [1]. The information available on the World Wide Web could influence people’s decision to accept, delay or refuse vaccination [4,5], and this may have facilitated outbreaks of vaccine-preventable diseases among unvaccinated populations [3]. Social media sites allow users from different countries to have public discussions about any topic, including vaccination, in real-time. Social media is a platform for real-time surveillance of vaccine-hesitancy and infectious diseases and a useful communication tool for global health actors [8]

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