Effectiveness and implementation of electronic decision support for adult vaccination in primary care: a mixed-methods quasi-experimental evaluation

Background Adult vaccination remains suboptimal despite frequent primary care contact. We evaluated changes in vaccination uptake associated with implementation of the Intelligent Vaccine Educational Prescription System (IVEPS) and examined implementation factors.Methods We conducted an explanatory sequential mixed-methods study in Shenzhen, China. IVEPS was introduced in 40 community health centers (CHCs) during June–November 2025. After common-support restriction, 298 CHCs (31 treated, 267 never treated) were analyzed using ATT-IPW Sun–Abraham staggered difference-in-differences models. Interviews with 21 stakeholders from 10 CHCs were analyzed using the Consolidated Framework for Implementation Research.Results IVEPS was associated with increased PPSV23 vaccination (ATT = 0.00249, 95% CI 0.00104–0.00394; p < 0.001), equivalent to 249 additional vaccinations per 100,000 eligible residents. Associations were not significant for influenza (ATT = 0.00105; p = 0.185) or herpes zoster (ATT = 0.00046; p = 0.097). Residual pre-intervention trends for PPSV23 and herpes zoster warranted cautious interpretation. Interviews suggested that digital prompts supported recommendations, while limited consultation time, incomplete workflow linkage, and affordability concerns constrained conversion.Conclusions IVEPS facilitated integration of adult vaccination recommendations into routine primary care, but increased recommendation did not consistently translate into higher vaccination uptake. Combining digital decision support with downstream implementation support may be important for improving vaccination conversion.