Background:

Nationwide measles immunization campaigns are resource-intensive yet can fail to reach the same children who are not reached by routine immunization services. Alternative approaches to better reach missed communities and improve efficiency focus on identifying and reaching unvaccinated, “zero-dose” children. Understanding the scope and impact of these strategies can inform approaches to fill immunity gaps and reduce measles disease burden.

Objectives:

We conducted a scoping review to map the existing literature on supplemental strategies used to reach zero-dose or under-vaccinated children in low- and lower-middle-income countries (LLMICs).

Eligibility criteria:

Our review focused on the “reach” component of the Identify-Reach-Monitor-Measure-Advocate (IRMMA) framework. We included literature describing vaccination interventions for measles-rubella, polio, and the Essential Program on Immunization (EPI) in LLMICs published from 2010 to 2021 in multiple languages. We excluded papers that solely focused on non-selective national vaccination campaigns.

Sources of evidence:

We searched peer-reviewed databases (PubMed, WorldWideScience, and Scopus) and gray literature in World Health Organization (WHO) regional databases, the WHO Institutional Repository for Information Sharing, and John Snow, Inc. resource libraries.

Charting methods:

Screening and extraction were conducted in Covidence. We iteratively coded, classified, and analyzed extracted data. Interventions were classified into the IRMMA framework categories: demand generation, human resources, supply chain, and service delivery.

Results:

Of 9450 articles screened, 185 met criteria for inclusion in the final analytic set. Strategies consisted of enhancements to the routine immunization program, with service delivery being the most frequent, followed by demand generation. Many studies described the integration of multiple strategies, offering opportunities to maximize reach and impact.

Conclusion:

The vaccination strategies other than campaigns described in this review have been implemented in multiple countries; some demonstrate greater potential to reach zero-dose and under-vaccinated children. In the face of an evolving funding environment, prioritizing interventions that are most likely to reach unvaccinated children is key.

Plain language summary

Immunization strategies to reach unvaccinated children

Large measles vaccination campaigns use a lot of resources but still often miss the same children who don’t get routine vaccines. To fix this, some health programs try new ways to find and vaccinate children who have not received any vaccines—called “zero-dose” children. This study reviewed existing research to understand which strategies work best to reach these children in low- and middle-income countries.

The review looked at programs focused on reaching children with vaccines for measles-rubella, polio, and other routine immunizations. It included studies published between 2010 and 2021 and excluded ones that only looked at national mass campaigns.

Researchers reviewed 9,450 articles and found 185 that matched their criteria. The most common strategies involved improving how and where vaccines are given (service delivery), followed by efforts to increase demand for vaccines. Many programs used a mix of approaches to be more effective.

In summary, there are many strategies beyond large campaigns that have been used in different countries to reach unvaccinated children. Some of these approaches may be more effective and should be prioritized, especially as funding becomes more limited.