Evaluating the Importance of Policy Amenable Factors in Explaining Influenza Vaccination: A Cross-sectional Multinational Study

Despite continuous efforts to improve influenza vaccination coverage, uptake among high-risk groups remains suboptimal. Vaccination decisions are shaped by various factors, including demographic, socioeconomic, and sociopsychological factors. The latter are inherently amenable to policy and interventions to change behaviour, but many studies evaluating the link between sociopsychological factors and influenza vaccination suffer from weaknesses - e.g., they do not use multivariable analysis, thus the importance of a given variable in relation to others often remains unknown. In order to assist in the monitoring of vaccination sentiment and the prioritisation and design of communication strategies and interventions to increase influenza vaccination across different contexts, this study aimed to answer these research questions: (i) What are the variables that consistently explain recent influenza vaccination uptake? (ii) What is the importance of policy-amenable factors in relation to demographic, socio-economic, and health characteristics in explaining past vaccination behaviour? (iii) Are the factors associated with influenza vaccination comparable across countries?

Between March and April 2014, a stratified random sampling strategy was employed with the aim of obtaining nationally representative samples in France (n = 787), the United Kingdom (UK) (n = 791), and the United States (US) (n = 814) through online databases and random-digit dialling. Participants were asked about vaccination practices, perceptions, and feelings. Multivariable logistic regression was used to identify factors associated with past influenza vaccination.

Overall, the responses of vaccinated and unvaccinated participants were significantly different (p<0.05-0.001) and comparable across countries. For instance, those who were vaccinated were: more likely to report that their physician and relatives thought they should vaccinate, more concerned about the risks of influenza, less worried about the risks of the vaccine, more trusting of vaccine manufacturers and providers, more prone to let physicians make decisions about their health (US/UK), less likely to have had a bad vaccine- or injection-related experience (UK), and more likely to have had a scary health-related experience in childhood than unvaccinated participants.

When all variables were assessed concurrently, the models that best fit the data explained 73% of the variance in past vaccination behaviour in the US, 80% in the UK, and 64% in France. Sociopsychological variables were found to consistently explain most of the variance in past influenza vaccination behaviour, over and above demographic, socioeconomic, and health variables (49% vs. 22% in the US, 42% vs. 38% in the UK, and 45% vs. 19% in France). The findings also show that the most important policy-amenable factors were social influence, particularly physicians' (US=14%, UK=21%, and France=25% of the variance), and perceptions about influenza (US=30%, UK=17%, and France=18% of the variance). According to the researchers, communication efforts should, therefore, focus on these factors.

Among the findings that the discussion section of the paper unpacks is the fact that perceived vaccine knowledge (to make informed decisions) was negatively correlated with past vaccination in the US and positively correlated in the UK. Researchers have long advocated for strategies to increase knowledge about vaccines, yet these results suggest that a cognitive approach may not always be effective, particularly when the intended population (e.g., unvaccinated people in the US) perceive themselves as being knowledgeable, and hence are less likely to seek or be receptive to further information.

The researchers examine the policy implications of the study, pointing out: "If we are to improve or at least sustain current immunisation rates, we must start actively listening to the public by including these [sociopsychological] aspects into national immunisation....Sociopsychological factors could provide a valuable opportunity to develop and evaluate targeted interventions to improve vaccination coverage. For instance, the influence of physicians' opinions on vaccination, over and above people's trust in immunisation stakeholders (including physicians themselves), indicates that improving communications at the practice level should be prioritised. One possible intervention is to reach undervaccinated groups (eg, younger eligible individuals) via consultations and vaccination reminders, a strategy that has been successful in older populations..."

Furthermore, "[e]fforts could also focus on addressing the gap between perceived and real risks of influenza. This could be achieved by moving away from generic messages about the threat of influenza (eg, 'influenza is serious') towards tailored messages that take into consideration the needs and characteristics of different at-risk populations....Similarly, effective communications as part of the consultation aimed at assuaging concerns around vaccines could take into account decision-making preferences and individual past experiences, particularly in the UK. For instance, communication efforts are likely to be better spent on those who prefer to make decisions about their heath independently than those who are more prone to delegate health decisions to their physician....[I]ncreased investment in the provision of training, adequate communication materials and decision aids to enhance patient–doctor communication is urgently needed and much deserved."

The researchers continue: "Messages delivered in primary care settings could also be complemented with evidence-based mass communications. For example, a national campaign could combine messages about the risks of influenza (eg, likelihood of catching it and feelings of vulnerability and regret for not vaccinating) with messages about the limited protectiveness of avoidance strategies (eg, taking vitamins or evading crowds), and provide - rather than avoid - easy-to-under-stand and accurate information about vaccine safety (eg, communicating more effectively the difference between vaccine-induced symptoms and actual influenza symptoms) and effectiveness, particularly in the USA. When possible, mass communications should also be tailored to specific at-risk populations."

In conclusion, the results "highlight the importance of routinely monitoring vaccination sentiment and using these data to inform immunisation policy."