Interventions to Vaccinate Zero-Dose Children: A Narrative Review and Synthesis

"[T]he evidence and key informants suggested that due to various socio-cultural, economic, and political factors that hamper efforts to vaccinate zero-dose children in different settings, diverse interventions are required to overcome those barriers."

Reaching zero-dose children is critical to both achieving equity and reducing the burden of communicable diseases globally. Barriers to reaching children who have not received any routine vaccination include economic, political, and socio-cultural factors. The challenge ahead lies in identifying zero-dose children and vaccinating them, which requires gaining a deeper understanding of potential interventions, both within and outside of the health sector, to reach zero-dose children. This narrative review is designed to contribute to that understanding.

The researchers reviewed the peer-reviewed and grey literature and identified 27 relevant resources. Exclusion criteria were repetition of information, non-English language, non-low-and-middle-income (non-LMIC) settings, and publications before 2010. In addition, they conducted 6 key informant interviews with the lead authors of highly relevant articles and the implementing organisations working on last-mile delivery efforts for vaccination.

Data were organised into 3 priority settings: (i) urban slums, (ii) remote or rural communities, and (iii) conflict settings. Zero-dose children in each of the 3 priority settings face differing barriers to vaccination, such as, in urban slums, a lack of caretaker knowledge, mothers' lack of autonomy, and distrust of the government or public health authorities. Therefore, context-specific interventions are required, such as leveraging slum health committees for urban slums or integrating with existing humanitarian response services for conflict settings.

Three predominant themes emerged for grouping the various interventions:

1. Community engagement: Key informants stressed that community involvement and participation are essential to reinforcing efforts to reach zero-dose children. Particularly, gaining trust and reliability is key to mobilising urban communities. For instance, a community's cultural norms must be understood to tailor appropriate messages for vaccination. In countries such as Afghanistan and Nigeria, religious and traditional leaders were involved in promoting vaccination in fragile areas and conducting door-to-door outreach vaccination programmes. These leaders received non-monetary incentives to recognise their work. Moreover, co-creating interventions with community assets such as informants, influential members, and survivors of vaccine-preventable disease, such as polio survivors, enhances ownership and strengthens trust in tailoring the crucial components of the vaccination services. Similar to urban slum communities, key informants stressed how vaccination interventions should engage with diverse remote and rural communities. This concept was exemplified in two Indian states, where drum beating was used as a culturally appropriate, low-cost, and scalable method to alert communities about vaccination days for children in remote populations. Engaging community leaders, particularly religious leaders, would also be key to reducing the number of zero-dose children in remote and rural settings.
2. Health systems' strengthening and integration: For example, integrating health services to enhance trust in vaccinations and health systems can especially help amplify the efforts to reach zero-dose children in remote or rural communities. My Village My Home (MVMH) is a community-level tool used in remote areas of India, Malawi, and Timor-Leste to record the births and vaccination dates of every infant in a community. This poster-sized material helps community-level workers visually assess the vaccination status of all infants born within a year and to easily identify those who remain unvaccinated. In conflict settings, some zero-dose children may not be registered with the health system and therefore would lack a vaccination card or even a birth record. Some tested interventions include Village Reach's Electronic Immunization Registries (EIR) programme and the International Red Cross's mReach tracing data platform, which enable health workers to register children and track their vaccination status. Disruptions in data sharing and misinformation are quick to take hold in conflict settings; hence, data and monitoring are critical not only for individuals but also for facilities.
3. Technological innovations: Contemporary technological solutions for real-time monitoring commonly include geospatial mapping that maps houses to priority populations and augment mass vaccination campaigns. Reveal, a geospatial modeling platform with aerial satellite maps, was used to identify built structures and locate zero-dose children in Zambia. This programme supports decision makers and intervention managers by guiding and tracking the delivery of in-field activities and identifying responsible teams for follow-up. Biometrics technology may be useful in tracking displaced zero-dose children.

This review has highlighted that the barriers to reaching zero-dose children are multifaceted and nuanced to each setting; therefore, no one intervention is enough. In particular, for technological interventions to be effective and sustainable, they should be supplemented with initiatives that aim to improve vaccine acceptance in communities and integrate these interventions into the existing primary healthcare structures. For instance, drones can cause harm and skepticism in addition to doing good, so coupling such interventions with community engagement efforts would be important.

In conclusion: "Future evaluations, including cost-effectiveness studies, of the suggested interventions are urgently needed to guide scale-up, as the evidence-base around these interventions is relatively small."