Discussion
SOC
INFLUENZA
This trial contributed to the literature by evaluating the efficacy of a theory-based online intervention and developing new methods to increase SIV uptake among adults 65 years or older. In line with our hypothesis, the SOC-tailored intervention was more effective than the non–SOC-tailored intervention in increasing SIV uptake among participants. The SIV uptake rate in the intervention group was 10 percentage points higher than the overall SIV coverage among all Hong Kong residents 65 years or older in the same influenza season (50.5% vs 40.4%).Several reasons might explain the higher SIV uptake in the intervention group. First, as documented by the intervention system, the SOC-tailored intervention helped in facilitating the intervention group to progress to a higher SOC, which might lead to the observed behavioral changes. Second, online interventions for the intervention group were guided by behavioral change strategies recommended by the TTM, whereas those for the control group did not involve such strategies. Theory-based interventions were more effective than non–theory-based interventions in facilitating behavioral changes.