Contents of Japanese pro- and anti-HPV vaccination websites: A text mining analysis
Introduction
Cervical cancer, which is commonly caused by chronic infection with an oncogenic strain of human papillomavirus (HPV), is the third most commonly diagnosed cancer and the fourth leading cause of cancer death in women worldwide [1], [2]. HPV vaccination is recommended by the World Health Organization [3] and has been made available in most industrialized countries. However, in some countries, HPV vaccination coverage is not as high as expected [4], [5], [6].
In Japan, the HPV vaccination rate for age-eligible young girls was as high as 70–80% in 2011 and 2012 [7]. In April 2013, the HPV vaccine became a routine prophylactic vaccine under the Preventive Vaccination Law in Japan, which recommended vaccination for all girls aged 11–16 years. However, at almost the same time, the Asahi Shimbun, one of the most authoritative and influential newspapers in Japan, publicized the case of a junior high school student who suffered from difficulties walking and performing mathematical calculations after receiving HPV vaccination. Similar cases were increasingly reported as adverse events gained media attention, though without sufficient proof of a causal relationship between vaccination and reported events. In consideration of public concerns about these events, the Japanese government suspended its proactive recommendation of HPV vaccination in June 2013. As a direct result, the HPV vaccination rate of age-eligible girls fell sharply to only a few percent by 2014 [8]. The safety of HPV vaccination is now a worldwide concern [9], [10]. In countries such as the United States, Greece, and Hong Kong, fear concerning adverse reactions to HPV vaccination is a significant reason for avoiding vaccination [11], [12], [13].
In many populations, anti-vaccination sentiment has existed in the form doubt, fear, and opposition to vaccination [14], [15]. This has had a demonstrable impact on vaccination policies, individuals, and community health [16]. Anti-vaccination messages are especially more common on the Internet than in other media forms [17]. The Internet is cited as one of the main sources of information on immunization for individuals struggling with vaccination decisions in different countries [18], [19], [20]. Individuals often use a general search engine and easily produced search terms (e.g., “vaccination”), and these terms return anti-vaccination websites in the top 10 hits [18], [21]. Importantly, these websites warn their readership against receiving HPV vaccination [21], [22]. HPV vaccination in Japan is no exception. Anti-HPV vaccination activists, who are mostly self-proclaimed specialists lacking specialized knowledge and some health professionals, propagate on the Internet that HPV vaccine has little or no efficacy yet carries a high risk of adverse side effects. Viewing an anti-vaccine website for merely 5–10 min increases perceptions of vaccination risks and decreases perceptions of vaccine omission risks [23]. Moreover, these decreased intentions to vaccinate persisted 5 months later [24]. Thus, HPV vaccination opposition online may incite fear concerning adverse events, stoke anti-vaccination sentiment, and ultimately prolong the HPV vaccination crisis in Japan. This urgent scenario prompted the present study.
We previously assessed the readability of pro- and anti-HPV vaccination websites and found that anti-HPV vaccination messages were easier to read than their pro-vaccination counterparts [25]. Readability of messages may contribute to their ease of acceptance by some audiences [25]. However, in addition to readability, contents of pro- and anti-cancer screening websites may also contribute to readers’ acceptance of one or the other position. Although studies have revealed contents of anti-vaccination websites [21], [22], [26], contents of Japanese anti- and pro-HPV vaccination websites are unknown. Therefore, we aimed to use a text mining method to examine frequently appearing contents on Japanese pro- and anti- HPV vaccination websites. We herein address three research questions: 1) what are the most frequently appearing contents on pro- and anti-HPV vaccination websites; 2) what are the distributions of these contents; and 3) who disseminates these contents.
Section snippets
Material collection
We conducted online searches on October 5, 2016 using a formula for Japanese-language input entered into the two most popular search engines in Japan, Google Japan (www.google.co.jp) and Yahoo! Japan (www.yahoo.co.jp), which respectively accounted for approximately 66% and 30% of all internet searches in September 2016 [27]. Although the English language has terms such as “vaccine,” “vaccination,” and “immunization,” the Japanese language only contains the terms “wakuchin” and “yobouseshu.”
Distribution by category
The interrater agreement was excellent (weighted kappa coefficient = 0.921). Of the 270 total materials evaluated, 137 materials (50.7%) propagated anti-HPV vaccination messages, 101 (37.4%) were pro-HPV vaccination, and 32 (11.9%) were “neutral” (Table 2). Of the 101 pro-HPV vaccination materials, 72 were by health professionals, 19 by mass media, and 10 by laypersons. Of the 137 anti-HPV vaccination materials, 20 were by health professionals, 35 by mass media, and 82 by laypersons.
Distribution of code-fitted paragraphs
Table 3 and
Discussion
We showed 16 frequently appearing contents (codes) on pro- and anti-HPV vaccination websites, as well as their distribution and disseminators.
“Side effects” was the most frequent content on both anti and pro websites (Fig. 1). This may have been because the evaluated pro websites attempted to provide unbiased discussion; therefore, they may have frequently referred to side effects despite their pro-vaccination position. The main disseminator of side effects was mass media on both pro and anti
Funding
This study was supported by JSPS KAKENHI (grant number 167100000384).
Conflicts of interest
None.
Acknowledgement
We thank Christina Croney, PhD, from Edanz Group (www.edanzediting.com/ac), for editing a draft of this manuscript.
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