Comparing the Quality of Pro- and Anti-vaccination Online Information

A Content Analysis of Vaccination-Related Webpages

Gabriele Sak; Nicola Diviani; Ahmed Allam; Peter J. Schulz


BMC Public Health. 2016;16(38) 

In This Article


According to the International Telecommunication Union,[1] currently almost 40 % of the global population (approximately 3 billion people) and 78 % of the developed world's population is online. Thanks to the Internet's persuasive force produced by the intersection of mass media and interpersonal communication elements, online health information seeking is becoming a recurrent activity of people's everyday life.[2–4] The majority of US internet users who have gone online to retrieve health information searched for health contents related to a particular disease or medical problem, and as a second most frequent "surfing activity" they looked for web sources describing a specific medical treatment or procedure.[4] The same portion of internet information seekers reported that their online health session started via a general search engine such as Google.[4] As Internet health consumers are now able to get access to multiple sources of health information without much effort, their level of knowledge and their social roles in the health domain might be affected. Depending on the quality of the information retrieved, the latter can impact people's attitudes toward a specific health topic and condition either beneficially or deleteriously.

The quality of health contents disseminated on the Internet has been a central focus for many researchers in the last decades. A systematic review showed that 70 % of 79 studies included found the general value of the information retrieved to be low, and another 20 % found it to be mediocre.[5] In response to criticism describing online health information as misleading, biased, highly technical, dated and fraudulent, different international and national bodies issued various codes of conduct in order to regulate and monitor the quality of health contents,[6,7] providing "a wide range of tools to assist site developers to produce quality sites and for consumers to assess the quality of sites" ([8] p. 598). Even though these protective initiatives often make use of rather similar quality criteria and set up similar ethical standards (e.g., disclosure of sources of information), their scope and application slightly differ.[9] These quality instruments can be grouped into five overarching types: "codes of conduct, quality labels, user guides, filters, and third party certification".[8] If, on the one hand, this emphasizes the growing need to assess the value of online health information, on the other hand it highlights the lack of consensus on the evaluation process that should be selected.[10]

Past evidence showed that vaccination is among the topics most frequently searched online.[11] Previous content analyses have shown that search engines list approximately as much anti-vaccination as pro-vaccination content.[11–13] However, to date, no evidence exists on differences in quality among pro- and anti-vaccination web contents. If the information disclosed by anti-vaccination web sources is of poor quality, there is a risk that part of the online population is exposed to wrong and hazardous information. Since "consumers may lack the motivation and literacy skills to evaluate information quality of health webpages",[14] the anti-vaccination movement might contribute to increasing unjustified fears, an insufficient vaccination uptake (when it is not a compulsory procedure), and a reemergence of infectious diseases that had almost disappeared in the advanced countries of the world. As a matter of fact, monitoring and assessing the value of online vaccination information appears to be a fundamental step in enhancing the quality of web-based health contents, which might consequently enable individuals to make better health decisions and adopt healthier behaviors.

To date, few content analyses of online vaccination websites have been conducted. As they are often narrowly aimed towards single immunizations (e.g., specifically on HPV vaccination:[15–17]), and as all past assessments on the typology of online vaccination information found a growing amount of anti-vaccination content,[11,18–21] the current study intends to define and compare the quality attributes of pro- and anti-vaccination sources, and in doing so to include multiple types of immunizations.