Abstract / Summary
Background: /Objectives: The global rollout of COVID-19 vaccines faced significant implementation challenges: limited adult immunization infrastructure, particularly in low- and middle-income countries; rapidly shifting viral epidemiology driven by emerging variants; and widespread vaccine misinformation that fueled hesitancy. Achieving the high coverage necessary to curb transmission required urgent attention to demand-side barriers, making the identification of effective interventions a critical public health priority. This systematic review synthesized global evidence on communication, behavioral, and health systems interventions to increase COVID-19 vaccine demand and uptake. The review assessed intervention effectiveness across diverse population groups and settings and identified lessons to inform the design of adult vaccination programs and future outbreak response.
Methods: Between March 2022 and July 2024, we performed a systematic search in PubMed, Scopus, and Global Index Medicus, for COVID-19 demand and uptake studies published after December 2020, with no language or geographic restrictions. Eligible papers were those that reported intervention studies with quantitative comparative outcomes on vaccination attitudes, appointment rates, uptake, or coverage following an intervention. Study quality was assessed using adapted Critical Appraisal Skills Program (CASP) criteria. Studies were categorized into nine intervention approaches, based on an adapted communication and service-delivery taxonomy. Interventions operated at individual, systems, and structural levels. A narrative synthesis was combined with vote counting of studies with positive findings to understand what intervention approaches were effective. and under what conditions.
Results: From over 23,000 records, 57 studies from 27 countries met inclusion and quality criteria. Most studies were conducted in high-income countries. Overall, 70% of studies reported positive findings on at least one vaccination outcome. Educational interventions were the most frequently studied approach and were most effective when delivered through multiple channels by trusted messengers and integrated with complementary strategies, rather than as standalone information provision. Reminder and nudge interventions showed mixed results, performing best when embedded within multicomponent approaches that addressed both logistical and attitudinal barriers. Access-enhancing and service delivery interventions demonstrated the most consistent evidence of effectiveness, with nine of ten studies reporting positive outcomes; successful approaches included on-site vaccination, mobile units, pharmacy and community health worker delivery, and integration into existing healthcare touchpoints. Vaccine mandates demonstrated the strongest and most consistent effects on coverage at scale, though their coercive mechanism raises ethical considerations around autonomy, equity, and public trust.