Date Published: January 26, 2017
Publisher: Public Library of Science
Author(s): Philipp Schmid, Dorothee Rauber, Cornelia Betsch, Gianni Lidolt, Marie-Luisa Denker, Benjamin J. Cowling.
Influenza vaccine hesitancy is a significant threat to global efforts to reduce the burden of seasonal and pandemic influenza. Potential barriers of influenza vaccination need to be identified to inform interventions to raise awareness, influenza vaccine acceptance and uptake.
This review aims to (1) identify relevant studies and extract individual barriers of seasonal and pandemic influenza vaccination for risk groups and the general public; and (2) map knowledge gaps in understanding influenza vaccine hesitancy to derive directions for further research and inform interventions in this area.
Thirteen databases covering the areas of Medicine, Bioscience, Psychology, Sociology and Public Health were searched for peer-reviewed articles published between the years 2005 and 2016. Following the PRISMA approach, 470 articles were selected and analyzed for significant barriers to influenza vaccine uptake or intention. The barriers for different risk groups and flu types were clustered according to a conceptual framework based on the Theory of Planned Behavior and discussed using the 4C model of reasons for non-vaccination.
Most studies were conducted in the American and European region. Health care personnel (HCP) and the general public were the most studied populations, while parental decisions for children at high risk were under-represented. This study also identifies understudied concepts. A lack of confidence, inconvenience, calculation and complacency were identified to different extents as barriers to influenza vaccine uptake in risk groups.
Many different psychological, contextual, sociodemographic and physical barriers that are specific to certain risk groups were identified. While most sociodemographic and physical variables may be significantly related to influenza vaccine hesitancy, they cannot be used to explain its emergence or intensity. Psychological determinants were meaningfully related to uptake and should therefore be measured in a valid and comparable way. A compendium of measurements for future use is suggested as supporting information.
Influenza is a significant health threat in our world today. For instance, seasonal influenza alone leads to an estimated 3 to 5 million cases of severe illness, and about 250,000 to 500,000 deaths globally each year . Most deaths associated with influenza occur among the most vulnerable members of the world population, i.e. very young children, the elderly and chronically ill patients. Despite influenza’s severity and the availability of safe vaccines, low influenza vaccine uptake rates within specific risk groups remain a challenge throughout the globe and contribute to the burden of disease . The scope of the issue became particularly clear during the 2009–2010 H1N1 pandemic . Vaccine uptake in the general public was very low, with countries reporting less than 50% of the expected coverage in target populations all over the globe (; Europe:  China: ; Australia: ; USA: ). Even more worrying is the fact that vaccine uptake in high risk groups, such as pregnant women  and the elderly , were similarly low.
On the micro-level, sociodemographic variables such as gender and age were the most reported, but also most inconsistent predictors of influenza vaccination. Besides this, lacking cues to action, low perceived utility of vaccination, a negative attitude towards influenza vaccines, and fewer previous influenza vaccinations were most frequently and consistently identified as significant barriers to influenza vaccination. In the following discussion we will first discuss differences between pandemic and influenza vaccine hesitancy and then summarize the evidence for each risk group stratified for pandemic and seasonal influenza vaccination. In doing this, we will first summarize the most important micro-level determinants and then synthesize the results based on the macro-level model of vaccine hesitancy. The macro-level synthesis intends to inform the design of future interventions to increase influenza vaccine uptake and thus supports our second research goal . Fig 4 gives a detailed overview of which barriers we allocated to which of the four hesitancy reasons, i.e. lack of confidence (e.g. negative attitude towards vaccines, decreased trust in authorities), complacency (e.g. decreased perceived risk of the disease, decreased worry about the disease), calculation (e.g. decreased belief: benefit of vaccines outweighs risks), and inconvenience (increased financial costs of vaccine, decreased frequency of interaction with healthcare service). Fig 4 also provides an overview of the findings collapsed across risk groups and influenza types. Fig 5 visualizes the number of significant results supporting each reason for hesitancy for each risk group and for pandemic (grey bars) and influenza vaccination (black bars).