Sentiment Analysis of Social Media on Childhood Vaccination: Development of an Ontology

"[I]t is important to monitor antivaccine arguments and rumors posted on the social media that might increase negative sentiment toward vaccination."

Although vaccination rates are above the threshold for herd immunity in South Korea, a growing number of parents have expressed concerns, including increasingly on social media, about the safety of vaccines. With the goal of preventing reduction in vaccine uptake by identifying concerns about and sentiments toward childhood vaccination, this study sought to develop a childhood vaccination ontology to serve as a framework for collecting and analysing social data on childhood vaccination. The idea is that an ontology can help researchers understand the semantics of and the relationships between concepts appearing in social data.

As reported here, the internet usage rate of Koreans aged 20 to 30 years who can be parents of young children is as high as 89.5%. In fact, there are about 45,000 parenting communities in the online cafes of the 2 most popular Web portals in South Korea, Daum and Naver. Thus, data on childhood vaccination can be obtained, and vaccination issues and sentiments can be identified. Vaccination issues in this study were defined as opinions, perceptions, concerns, and worries about vaccines and vaccination posted on social media. Sentiments in this study were defined as feeling and emotion on childhood vaccination posted on social media.

Ontology development was an iterative process consisting of 5 steps, which involved, for example, identifying 5 existing models of vaccination decisions and hesitancy. The researchers determined the domain and scope of the ontology from personal perceptions, behaviour, and experiences of vaccination as well as social, environmental, institutional, and political factors related to vaccination based on 21 competency questions. Ultimately, the process led to a childhood vaccination ontology comprised of 9 superclasses (child, parent, family and friend, organisation and institution, society and community, policy, vaccination intention, vaccination behaviour, and vaccination experience) and 124 subclasses, with 4 levels of depth and a terminology containing 882 synonyms for class, attribute, and value concepts. One of the features of this ontology is that it is not limited to factors affecting vaccination but also includes intention before vaccination, vaccination behaviour, and experience after vaccination.

In total, 40,359 Korean posts on childhood vaccination were collected from 27 social media channels between January and December 2015. Vaccination issues were identified and classified using the second-level class concepts of the ontology. The sentiments were classified in 3 ways: positive, negative, or neutral. Posts were analysed using frequency, trend, logistic regression, and association rules.

The researchers learned that the most common vaccination issue was parents' health belief, which appeared in 53.21% of posts. Positive sentiments appeared in 64.08% of posts, which was 2.5 times more than negative sentiments. Trends in sentiments toward vaccination were affected by news about vaccinations; for example, positive sentiments increased when news encouraging vaccination, such as vaccination campaigns, was announced, whereas negative sentiments increased when news about epidemic outbreaks, such as the measles outbreak in the United States, was announced. Posts with parents' health belief, vaccination availability, and vaccination policy were associated with positive sentiments, whereas posts with experience of vaccine-adverse events were associated with negative sentiments. Therefore, the researchers suggest, it is important to inform the public of vaccination policy, the benefits of vaccination, and how to deal with adverse events to lower negative sentiments, which can affect vaccination intention or behaviour.

Because health belief may be influenced by antivaccine arguments, the researchers conclude that it is important to monitor antivaccine arguments and rumours posted on social media that might increase negative sentiment toward vaccination. Vaccination availability is related to vaccination policy, so they recommend publicising policies on free vaccinations to improve positive sentiments toward vaccination.

In conclusion, the researchers write: "practitioners and researchers in the field of childhood vaccination could use our ontology to identify concerns about and sentiments toward childhood vaccination from social data."