BACKGROUND: The safety and efficacy of influenza vaccination for the chronically ill are clearly supported by the evidence, yet vaccination rates in this vulnerable popu- lation remain low. This leads to many avoidable hospitalizations and deaths in Germany every year. The goal of this systematic review is to identify measures in primary care medicine that can be used to increase influenza vaccination rates among the chronically ill. METHODS: This review was carried out as recommended in the PRISMA statement. A systematic literature search was performed. Only randomized, controlled trials were included in the analysis. Details can be found in the study protocol (PROSPERO, CRD42018114163). RESULTS: 15 trials were included in the analysis. Training sessions for medical practice teams focusing on a particular disease raised the vaccination rates by as much as 22%. A financial incentive had the greatest effect (relative risk [RR]: 2.79; 95% confidence interval: [1.18; 6.62]). Reminders via text message yielded a maximum 3.8% absolute increase in vaccination rates. Complex interventions were not found to be of any greater benefit than simple ones. CONCLUSION: A variety of approaches can be effective. Focusing training sessions for medical practice teams on certain diseases may be of greater benefit than vacci- nation-centered training sessions. Reminder systems for doctors should be more reliably implemented. Simple strategies are perhaps the most suitable ones in the heterogeneous population of chronically ill persons. The limitations of this system- atic review include the heterogeneity of the studies that we examined and the small number of studies in each category.
