Exploring supplemental immunization strategies to reach zero-dose children in low- and middle-income countries: a scoping review

This peer-reviewed article presents a scoping review of supplemental immunization strategies used to reach zero-dose and under-vaccinated children in low- and lower-middle-income countries. The review maps evidence published between 2010 and 2021 on strategies for measles-rubella, polio, and routine immunization, excluding studies focused only on non-selective national vaccination campaigns. The authors classified interventions using the “reach” component of the Identify-Reach-Monitor-Measure-Advocate framework, covering service delivery, demand generation, human resources, and supply chain approaches.

Key findings

• The review screened 9,450 records and included 185 articles, with India, Nigeria, and Pakistan the most frequently represented countries.
• Most studies focused on service delivery interventions, including RED/REC, microplanning, outreach sessions, community immunization points, child health days, and periodic intensification of routine immunization.
• Demand generation was also common, especially social mobilization, reminders and recall systems, and information, education, and communication activities.
• More than 40% of included studies described multi-component strategies, suggesting that combined and locally tailored approaches may be particularly important for reaching missed children.
• Evidence on costs, efficiency, long-term sustainability, and intervention-specific impact remains limited, highlighting a need for more implementation and economic research.

Thumbnail image credit: Gavi