Vaccine comparison

Chen, Q., Croitoru, A., & Crooks, A. (2023). A comparison between online social media discussions and vaccination rates: A tale of four vaccines. Digital Health, 9, 20552076231155682.

The recent COVID-19 pandemic has brought the debate around vaccinations to the forefront of public discussion. In this discussion, various social media platforms have a key role. While this has long been recognized, the way by which the public assigns attention to such topics remains largely unknown. Furthermore, the question of whether there is a discrepancy between people’s opinions as expressed online and their actual decision to vaccinate remains open. To shed light on this issue, in this paper we examine the dynamics of online debates among four prominent vaccines (i.e., COVID-19, Influenza, MMR, and HPV) through the lens of public attention as captured on Twitter in the United States from 2015 to 2021. We then compare this to actual vaccination rates from governmental reports, which we argue serve as a proxy for real-world vaccination behaviors. Our results demonstrate that since the outbreak of COVID-19, it has come to dominate the vaccination discussion, which has led to a redistribution of attention from the other three vaccination themes. The results also show an apparent discrepancy between the online debates and the actual vaccination rates. These findings are in line with existing theories, that of agenda-setting and zero-sum theory. Furthermore, our approach could be extended to assess the public’s attention toward other health-related issues, and provide a basis for quantifying the effectiveness of health promotion policies. Figure 1 displays an overview of the research outline.

Introduction

The recent coronavirus (COVID-19) pandemic has brought considerable attention to vaccinations. Today, the discussion on vaccinations cuts across a multitude of issues, ranging from topics such as ef cacy, safety, and trust, to topics related to ethical, religion, and personal liberties to name a few. It has also attracted participation among diverse audiences such as policymakers and government agencies, health professionals, scientists, various advocacy and interest groups, and the public at large. Although the current discussion around vaccinations may seem a relatively recent phenomenon, it is, to a large extent, but one chapter in a longstanding public discussion spanning over more than two centuries, which revolved around “pro–" and “anti–” vaccination debates and social movements. The contemporary public discussion about vaccinations occurs largely online, and in particular on social media.

This use of online platforms not only impacts the vaccination discussion itself but also more broadly the way by which vaccine related information is consumed and produced. While the use of online platforms in the context of vaccinations has attracted considerable attention, the interplay between participation in vaccination discussion and actual vaccination-related behaviors is not yet fully understood. This paper aims to explore this interplay through the lens of public attention as it is captured by online social media. It is necessary to point out that the term "interplay" here refers to the potential impact of social media on human actions, which has been studied elsewhere. In other words, our basic premise is that social media can impact human behavior. Based on this premise, we examine how public attention is allocated across several vaccination types, and then compare it with actual vaccination rates. Our analysis takes advantage of the recent COVID-19 pandemic which has evidently attracted much attention in the online public vaccination-related discourse, thus providing a unique opportunity to explore how the public assigns attention to vaccinations in the presence of a major disruptive public health event.

The overall approach in investigating these questions is by focusing on four distinct vaccinations, namely COVID-19, In uenza, Measles, Mumps, and Rubella (MMR), and Human Papillomavirus (HPV). This set of vac- cinations allows us to compare public engagement (and attention) and vaccination rates across the different vaccines and assess the impact of the COVID-19 vaccination debate on public engagement. Our assessment of public engagement and attention distribution among the various vaccines in social media focuses on Twitter due to its prominent role in vaccine-related debates. While public attention is often dif cult to quantify, one approach to assessing it is through monitoring and analyzing the ebb and ow of online discussion on social media platforms (e.g., Twitter), an area that has received increasing attention in recent years in public health studies. To that end, we analyzed a data set covering 2015 to 2021 in terms of tweet message volumes that is used as a proxy for public engagement and attention.

As the Greek philosopher Aristotle said, "Man is by nature a social animal," and it is through the interaction of various media that we communicate and disseminate information. Over time, the medium of dissemination has evolved, from handwritten papal bulls, the printing press, to wireless communication technologies, such as radio and television broadcasting. Such evolution enabled the dissemination of audio and visual content to a more and more broader audience both nationally and internationally. For example, by the late twentieth century, around 98% of households owned at least one television.

Today printed and broadcast media, often referred to as "vertical media,” aims to cover potential interests and topics, and has become an integral part of modern society. Consequently, considerable research has been dedicated to the study of mass communication and the underlying principles and theories that govern it. In the context of our research, there are two key related theories that are of particular importance for our analysis: the agenda-setting theory and the zero-sum theory.

Agenda-setting theory, generally examines the relationhip between the media and the public agendas with respect to a speci c topic, highlighting that the media can affect the salience of issues in the public agenda. In earlier agenda-setting studies, it was argued that the media could not only in uence what people think about, but also how they think about it. This early work has spurred research investigating the impacts of the media on the public’s perceptions with respect to politics, economics, and public health. In the context of public health, several authors have noted the role of agenda setting played by the media in in uencing health-promoting change.

The rise of Web 2.0 has sprung renewed interest in agenda-setting in the context of social media due to the ability to facilitate“two-way communication”. Such technologies, also called "horizontal media", emphasize the importance of the individual and reduce the barriers to user participation. Various studies have explored the applicability of agenda-setting theory in the digital age, as well as how social media shape public discourse and attitudes towards speci c topics.19,22,33–35 One example of this is how the agenda can be in uenced by the networked association of issues through social media.

A second, related theory, that is of particular importance to our research is the zero-sum theory. This theory, which can be seen as complementing the agenda-setting theory, is based on the premise that human (and by extension the public’s) attention is nite, which leads to a competition among the various issues in the media in which increased attention to one issue will lead to a decrease in attention given to other issues. Like the agenda-setting theory, the zero-sum theory was originally proposed in the context of vertical media (i.e.,“one-way” communication). More recent studies which have examined this theory in the context of social media suggested its applicability is given the inherent nite nature of human attention regardless of the subject matter at hand.

Turning back to the study of social media on health-related topics, we are especially interested in the online debates regarding vaccination under this context. Looking back at disease outbreaks over the past two decades, such as the Ebola and Zika viruses and the current COVID-19 pandemic, they all have substantially impacted, to varying degrees, on our environment, economy, and society as a whole.43–50 Therefore, developing vaccines, especially for vaccine-preventable diseases, has become crucial to preventing the spread and thereupon helping the world return to somewhat normalcy.

As mentioned above, the discussion regarding vaccination has been longstanding but with disparate voices. Pro-vaccination supporters urge the importance of vaccination for public health, whereas anti-vaccination groups argue their concerns about safety, religious and philosophical beliefs, which has made the vaccination debate polarized over time. This is especially the case today with mass communication through social media. Social media enables individuals to share their opinions about vaccinations online, but at the same time puts them in an information "dye vat,” in the sense there are all sorts of words (either positive or negative) about vaccinations that can become mixed together and alter people’s perceptions of vaccination. It is through such exposure that an individual’s perception towards vaccination might change under the impacts of various information traffic, resulting in diverse vaccination sentiments, and thereafter, making vaccination campaigns more challenging. In this regard, it is crucial to understand how the public’s attention maps to various vaccination-related themes on social media, especially with respect to their limited attention capacity, and how such attention compares to the reported vaccination rates in reality. These questions have direct practical applications, such as topics around improving public health awareness and the effectiveness of health promotion policies.

Implementation and Results

In order to understand how public attention compares to reported vaccination rates, we collected actual vaccination rates for four distinct vaccines, namely COVID-19, Influenza, HPV, and MMR vaccines, from the United States Centers for Disease Control and Prevention (CDC).

• The COVID-19 vaccination dataset records the total number of people with at least one dose based on the jurisdiction where a recipient lives from Jan 2021 to July 2021.
• The influenza vaccination dataset consists of estimated seasonal influenza vaccination coverage from 2015 to May 2021, which is measured based on the National Immunization Survey-Flue (NIS-Flu) and the Behavioral Risk Factor Surveillance System (BRFSS).
• The MMR vaccination dataset documents the estimated MMR vaccination among adolescents from 2015 to 2021
• The HPV dataset records estimated HPV vaccination among adolescents with individuals at least one dose from 2016 to 2021.

To extract information about the population's attitude towards vaccination from the collected Twitter data corpus, sentiment analysis was performed. In the context of this project, we refer to sentiment analysis as Natural Language Processing (NLP) based techniques that focus on unraveling individuals’ opinions, attitudes, or emotions from text messages regarding to a specific topic - in our case, the online social media discussion about vaccination.61 In this study, we aim to classify tweets into one of three classes —“Pro-vaccine,” “Neutral,” and “Anti-vaccine”, and do so by integrating supervised machine learning with word embedding techniques.

Figure 2 shows the quarterly percentage of users from 2015 to 2021. Generally speaking, these show how the public's attention, while being finite due to the zero-sum theory, switches from one vaccination to another over time. For example, in the first half of 2015, the vaccination conversation about the MMR dominated the online discussion which can be attributed to the measles outbreaks in California, but the percentage of users gradually declined in the second half of 2015 as the public's attention switched to focusing largely on influenza during the winter period. More recently, they show the substantial redirection of public attention towards the COVID-19 vaccine in 2020. Since then, the dominance of the COVID-19 vaccine discussion has drawn the most public attention and has maintained its dominance until the end of the study period.

Figure 3 displays the temporal distribution of scaled odds ratio of vaccine discussion online (red color) as well as the scaled growth rate of actual vaccination offline (blue color) for the four different vaccines. Figure 3 also shows how the HPV and MMR vaccine rates are rather volatile at the yearly time granularity, without any apparent patterns in their trends in Twitter and actual vaccination rates. Nonetheless, we do observe a periodic change in the influenza vaccine, where the peak rate of flu vaccinations emerges close to the peak of the flu vaccine discussion on Twitter, and the peak regularly appeared during the winter period (i.e., flu season) (see Figure 3(b)).

To further help understand the underlying mechanism of how social media is shaping and influencing people’s perception and emotion towards vaccination, we classified users’ attitudes into three sentiments, namely pro-vaccine, neutral and anti-vaccine, and monitored the shifts of emotion with respect to different vaccines over time. Figure 4 presents the distribution of these sentiments with respect to the four different vaccines on a quarterly basis. The results show that in general, a positive vaccine sentiment is dominant, and the pro-vaccine users grow faster than the anti-vaccine group, indicating that the online vaccine discussion has the potential to enhance public awareness of the importance of vaccination.

Digging more into this, Figure 5 displays the changes in people’s emotions regarding the four vaccines over time. This figure clearly demonstrates the gradual shift from influenza, MMR, and HPV to COVID-19 after 2019 (the COVID-19 outbreak). Moreover, besides the feelings of fear, anger, and sadness concerning the COVID-19 vaccine, we observed more positive emotions in the online discussion, such as anticipation and trust. This again implies the positive nature of the social media discourse, and by extension the public awareness, of vaccination campaigns.