The relative effects of determinants on Chinese adults' decision for influenza vaccination choice: What is the effect of priming?

Objectives: To assess the relative effects of altering different factors (attributes) related to adults' decision for influenza vaccination choice, and whether priming modifies these relative effects.

Methods: Chinese adults were randomly allocated to either a control condition (non-risk related video), or one of the three health risk-priming conditions (disease (influenza) risk video, intervention (vaccine) risk video, or non-specific (air pollution) risk video), each comprising ∼200 participants, prior to a discrete choice experiment survey. Mixed logit modelling estimated the relative effects of pre-determined attributes influencing vaccination choice.

Results: Across all four conditions, for determining vaccination choice, Vaccine Efficacy had a greater effect than social cues (community vaccination coverage rate (CVCR) and doctors' advice) but social cues can compensate for the effect of "uncertain" vaccine safety; influenza case-fatality ratio (CFR) became dominantly important among all included attributes when it reached 20%; vaccination preference increased when a CVCR changed incrementally from 5% to 60% but declined thereafter when the CVCR reached 80%. Compared with Control participants, a CVCR increased by 80% had a smaller effect for participants primed by intervention risk on vaccination choice, while the effect of influenza risk relative to vaccine risk increased following disease risk priming.

Conclusion: While increasing confidence on vaccine efficacy is more important for influenza with less severe consequences, highlighting disease consequences becomes increasingly important when its CFR increases, for promoting vaccination uptake. For a new vaccine with uncertain safety, involving doctors and early vaccine takers to validate vaccine safety should be important. Brief exposure to influenza/vaccine risk didn't increase the effect of specific risk on vaccination choice but may change the relative weight of disease versus intervention risk when individuals make trade-off for vaccination decision. Free riding on herd immunity may increase when community vaccination coverage is high particularly following intervention risk priming.