Using the Health Action Process Approach and Implementation Intentions to Increase Flu Vaccine Uptake in High Risk Thai Individuals: a Controlled Before-after Trial

Objective: Influenza vaccination rates remain suboptimal in many countries, including Thailand. This study compared the effect of a theory-based educational leaflet, based on the Health Action Process Approach (HAPA), and action planning intervention with a standard government information leaflet designed to increase influenza vaccination uptake among high-risk Thai adults.

Design: A controlled before and after trial was conducted. Participants in the intervention (n = 99) received a leaflet based on the HAPA and asking them to form an action plan identifying where, when, and how they would seek vaccination. Those in the comparison condition (n = 102) received a standard government information leaflet.

Main Outcomes Measures: There are 2 sets of outcome measures: (a) process measures of HAPA related variables taken at T1 and T2, and (b) vaccination rates during the subsequent 2 months.

Results: The HAPA intervention resulted in greater changes on measures of risk perception, outcome expectancies, self-efficacy, and intention than the comparison condition. Stronger intentions to obtain vaccination were explained by changes in outcome expectancies, perceived self-efficacy for arranging time and transportation, and planning. No significant difference in vaccination rates was observed between two groups. Influenza vaccination was directly predicted by self-efficacy and intention.

Conclusion: Results demonstrate that a HAPA-based leaflet may be a useful tool to enhance individual's vaccination intention, but larger trials are required to confirm these findings.