How has the flu virus infected the Web? 2010 influenza and vaccine information available on the Internet

During the 2009–10 flu pandemic, compliance with preventive measures proposed by health authorities was not optimal. The presumed risks associated with vaccination attracted mass media attention, and risk perception among the public was high. Concerns regarding the population-based public health response to this pandemic focused on the need for more effective communication; a BMJ editorial cited an urgent need to restore public trust before the next pandemic comes along [1].

The Internet is increasingly used as a “trusted” source of health-related information, although our knowledge regarding the role of this source in shaping behaviour during a pandemic event is largely unknown. Of particular interest is the role of search engine algorithms, which mainly determine content visibility and user accessibility. Previous studies have investigated the role of different search terms in determining the search engine results. For example, keyword “vaccination” was found to lead to a greater amount of content with an adverse attitude towards vaccination compared to “immunization”, since the antivaccinationists have a strong philosophical preference for the former [2, 3].

Recent contributions have pointed out that research on online vaccine information is quite rare and not up to date [4], although there is evidence that exposure to critical websites is associated with changes in risk perception [5]. Previous studies have explored the contents of antivaccinationist websites, analysing their statements and arguments [6‐8], and the prevalence of quality markers in websites dealing with vaccination [9]. Other studies have analysed YouTube contents regarding immunization [10], including H1N1 influenza [11] and focused on the Internet’s influence on risk perception from a psychological perspective [12]. Regarding the specific issue of information about flu vaccination on the Internet, one study performed a content analysis of the information provided by the social network Twitter during the H1N1 outbreak [13]; another dealt with the probability of finding WHO recommendations on swine flu prevention [14]. A recent study has even investigated psychological and demographic factors associated with H1N1 vaccination, highlighting the critical role of communication strategies in shaping behaviour [15].

On the basis of the above considerations, this study aimed to evaluate online content regarding vaccination right after the 2009–10 pandemic in order to understand the role that Internet may have had in shaping people’s risk perception. To achieve this objective, we conducted an overall assessment of the websites providing flu vaccine information by evaluating their visibility (by rank analysis), and integrating this with a content analysis. Possible differences in the results provided by different search engines were also assessed.

An overall flow-chart of the analysis process is shown in Figure 1.

According to the above findings, the majority of the selected websites had a positive/neutral attitude to flu vaccination. They distinguished themselves from the adverse ones by some revealing features: firstly, greater transparency, in relation to more frequent declaration of the sources of funding; secondly, greater credibility, since in a statistically higher percentage of cases explicitly declared the website mission and the public to whom the information is addressed. In addition, their content always adhered to their stated mission (not the same for adverse websites) and they more frequently declared the owner’s name and credentials. Furthermore, they were characterized by higher data and privacy protection and by more professional appearance and consistent design. Lastly, they showed a significantly higher amount of copyrighted information, which can be considered as an expression of responsibility for content.

The quality of the information provided by pro/neutral websites was generally satisfactory. In particular, adherence to the gold standard was optimal, whereas data about completeness were less satisfactory, especially on websites dealing with seasonal flu vaccine.

The presence of information about vaccination period, risks and contraindications was statistically higher for the seasonal flu vaccine compared to the H1N1 vaccine, so it is possible to assume that the set of information available on the Web about the former is more exhaustive and scientifically structured. Completeness of the information about contraindications was also better for the seasonal vaccine, while information about doses was more complete for the H1N1 vaccine.

Previous studies have pointed out that the influence of Internet information on risk perception, decision process and hence vaccination behaviour does not always act in a conscious way; the fact that individuals do not admit to considering the Internet a reliable source does not necessarily mean that it does not influence their choices [22, 23]. Based on the above results, the way adverse websites were formulated seems to be consistent with the purpose of influencing the readers’ attitude towards vaccination. Some arguments were often repeated: danger of vaccine due to adverse affects and toxic constituents, economic interests driving vaccination policy (the “plot theory”), unreliability of institutional medicine. Furthermore, a narrative form widely prevailed. Such personal and emotional narration, frequently regarding children and performed between parents, has been proved to be a critical factor of the effects of antivaccinationist information [5, 23], since it works on readers’ emotions and fears.

Search engine ranking refers to the position at which a particular occurrence appears in the results of a search engine query. As a consequence, it is closely connected with visibility to users.

Differences were highlighted in the kind of results provided by the search engines. In particular adverse websites were shown on the first page by Google only, and Yahoo results were characterized by a higher presence of institution (.gov extension) in the first positions, which we expect to contain a more reliable information [24].

Page rank is a crucial factor based on what can be called “the internet paradox”: although the Web contains virtually unlimited information, it has been observed that users generally do not go beyond the first page of search engine results and have a low tolerance of going in depth through what is retrieved [25].

One particular strength of this study is that we performed a broad-spectrum analysis on different levels: visibility according to page ranking, analysis of the websites and analysis of the information provided, choosing for websites with opposing attitudes to flu vaccination the methods which most suited their features.

One limitation of the study is intrinsic to the Internet: information on the Web is constantly changing, whereas we analysed the Web pages which were available at a particular time. Since we carried out website selection in autumn 2010, some months after the flu pandemic peaked, we realise that page rank may well have changed in the meantime, as the topic was becoming of less pressing actuality.

Secondly, our assessment of the information provided using different methods of analysis, based on the websites’ attitude towards flu vaccination, was due to the very nature of the information. Actually, there was an extreme difference in the way pro/neutral and adverse websites were structured. Adverse websites, far from providing a structured set of information, as the pro/neutral ones did, showed a prevalence of narrative form, rich in dramatic personal experiences which were generally related to adverse reactions to the vaccine. The use of a fixed analysis scheme would have prevented us from assessing the highly intriguing topics and theories used by antivaccinationist authors to support their attitude and spread it among the people.

Moreover, Web 2.0 was excluded from the analysis. This was due to its extremely dynamic structure, which requires specific analysis strategies and makes it impossible to univocally assign an attitude to several comments, made by as many authors, on the same Web page.

Web 2.0 is continuously expanding and it is becoming a common way to obtain health information. Even important health institutions such as the CDC use the new communication tools, like mobile phone applications, in order to spread information among the population. We therefore suggest that a possible future development of the research could interestingly extend it to this area of the Internet, also in view of strategically exploiting its potential by the public health authorities.

Furthermore, we decided to limit the research to the two most commonly used search engines (Google.com and Yahoo.com), although others, such as Bing.com and Ask.com, are also very popular [16], and to a limited set of key phrases.

The vast majority of the websites analysed had a positive/neutral attitude towards flu vaccination and overall they provided satisfactory information. They also were characterized by a certain presence of reliable organisations and institutions, for example the CDC (Centers for Disease Control and Prevention) official website and Flu.gov (a government website managed by the U.S. Department of Health & Human Services). This naturally raises the question as to whether antivaccinationist information on the Web could take different routes, such as Web 2.0. If confirmed, this would entail a new challenge for the public health authorities. Promotion of prevention on the Internet by providing traditionally structured information may no longer be sufficient and the use of new strategies, such as Web 2.0 tools, may be more effective as they may be more likely to spread information via “viral” dissemination.