Facebook Recruitment of Vaccine-Hesitant Canadian Parents: Cross-Sectional Study

This study aimed to explore the use of Facebook as a tool to reach vaccine-hesitant parents in Canada, as compared with random digit dialing (RDD) methods. RDD surveys have historically been the "gold standard" in the collection of Canadian immunisation study data. However, Statistics Canada reports that more Canadian households are abandoning their traditional landline telephones. In addition, the majority (58%) of internet users are using social media, including over 86% of those under the age of 35. Concerns have been emerging in the public health community that parental fears regarding childhood vaccines are growing, largely due to rapid sharing of misinformation and the increasing expression and empowerment of anti-vaccine communities and activists on social media. Therefore, this study examines recruiting via social media platforms for web-based surveys as a viable alternative or complement to RDD to reach self-selecting higher risk populations, such as vaccine-hesitant parents.

The researchers recruited Canadian parents over 4 weeks in 2013-14 via targeted Facebook advertisements linked to a web-based survey. They compared methodological parameters, key parental demographics, and 3 vaccine hesitancy indicators (perception of safety of childhood vaccinations, measured on a 7-point scale; vaccination status of youngest child was classified as "completely up-to-date" or "partially or not at all up-to-date"; and difficulty in making the decision to vaccinate (or not vaccinate) their youngest child) to an RDD sample of Canadian parents. Two raters categorised respondent reasons for difficulties in deciding to vaccinate, according to the model of determinants of vaccine hesitancy developed by the World Health Organization (WHO)'s Strategic Advisory Group of Experts on Immunization (SAGE).

The Facebook campaign received a total of 4,792 clicks from unique users, of whom 1,696 started the web-based survey. The total response rate of fully completed unique web-based surveys was 22.89%, and the survey completion rate was 64.68%. The web-based sample yielded younger parents, with 85.69% under the age of 40 years as compared with 23.38% in the RDD sample; 91.43% of the Facebook respondents were female as compared with 59.26% in the RDD sample. Facebook respondents had a lower median age of their youngest child (1 year vs 8 years for RDD). When compared with the RDD sample, the web-based sample yielded a significantly higher proportion of respondents reporting vaccines as moderately safe to not safe (26.62% vs 18.57%, partially or not at all up-to-date vaccination status of youngest child (22.06% vs 9.57%), and difficulty in making the decision to vaccinate their youngest child (21.06% vs 10.09%). Out of the web-based respondents who reported reasons for the difficulties in deciding to vaccinate, 37.2% reported lack of knowledge or trust due to conflicting information, and 23.8% reported the perception of the risk of the adverse effects of vaccines being higher than the risk of disease acquisition.

According to the indicators, the web-based strategy was successful in reaching a population more likely to be engaging in health discussions on the internet and making decisions on childhood immunisations. Thus, this recruitment strategy was superior to the RDD methodology in reaching "at-risk" vaccine-hesitant parents. Moreover, one-fifth of the respondents who reported their child as not-up-to-date reported concerns over autism or sudden infant death syndrome as important reasons for deciding to not vaccinate their youngest child, even though it has been proven that neither disorder is associated with vaccination. The study found that the main reasons reported for difficulty in decision-making were the inability to decipher or trust all the information available and the difficulties in weighing the risks and benefits of immunisation with concerns over side effects and adverse effects. The contextual influence of media, social media, or other sources of communication may have contributed to respondent concerns regarding their own knowledge or risk perception. However, this could not be further probed because of the inherent limitations of web-based surveys.

Overall, Facebook was a successful recruitment method for parents to complete a web-based survey on vaccination. For both the web-based and RDD survey methods, data collection spanned the same time frame and individual surveys took approximately the same amount of time; however, the costs were 97% lower with web-based recruitment. "The quality of the data was evident with a rich pool of qualitative and quantitative data, a high completion rate, and little missing data." Engaged respondents provided insights into the most important determinants of vaccine hesitancy - information possibly helpful in directing any future intervention efforts. "With more Canadians abandoning landlines and interacting on the Internet with potential exposure to an abundance of anti-vaccination sentiment, popular social media platforms should be considered as part of any recruitment strategy or study on the determinants of vaccine-hesitant parents but also in the implementation of interventions to address these determinants. Future research should consider studies to investigate data reliability and to better examine the relative importance of contextual influences, such as the Internet, as determinants of vaccine hesitancy."