Measuring Zero-Dose Children: Reflections on Age Cohort Flexibilities for Targeted Immunization Surveys at the Local Level.

Zero-dose (ZD) children is a critical objective in global health, and it is at the heart of the Immunization Agenda 2030 (IA2030) strategy. Coverage for the first dose of diphtheria-tetanus-pertussis (DTP1)-containing vaccine is the global operational indicator used to estimate ZD children. When surveys are used, DTP1 coverage estimates usually rely on information reported from caregivers of children aged 12-23 months. It is important to have a global definition of ZD children, but learning and operational needs at a country level may require different ZD measurement approaches. This article summarizes a recent workshop discussion on ZD measurement for targeted surveys at local levels related to flexibilities in age cohorts of inclusion from the ZD learning Hub (ZDLH) initiative-a learning initiative involving 5 consortia of 14 different organizations across 4 countries-Bangladesh, Mali, Nigeria, and Uganda-and a global learning partner. Those considerations may include the need to generate insights on immunization timeliness and on catch-up activities, made particularly relevant in the post-pandemic context; the need to compare results across different age cohort years to better identify systematically missed communities and validate programmatic priorities, and also generate insights on changes under dynamic contexts such as the introduction of a new ZD intervention or for recovering from the impact of health system shocks. Some practical considerations such as the potential need for a larger sample size when including comparisons across multiple cohort years but a potential reduction in the need for household visits to find eligible children, an increase in recall bias when older age groups are included and a reduction in recall bias for the first year of life, and a potential reduction in sample size needs and time needed to detect impact when the first year of life is included. Finally, the inclusion of the first year of life cohort in the survey may be particularly relevant and improve the utility of evidence for decision-making and enable its use in rapid learning cycles, as insights will be generated for the population being currently targeted by the program. For some of those reasons, the ZDLH initiative decided to align on a recommendation to include the age cohort from 18 weeks to 23 months, with enough power to enable disaggregation of key results across the two different cohort years. We argue that flexibilities with the age cohort for inclusion in targeted surveys at the local level may be an important principle to be considered. More research is needed to better understand in which contexts improvements in timeliness of DTP1 in the first year of life will translate to improvements in ZD results in the age cohort of 12-23 months as defined by the global DTP1 indicator.

Combining cluster surveys to estimate vaccination coverage: Experiences from Nigeria's multiple indicator cluster survey / national immunization coverage survey (MICS/NICS), 2016-17.

In 2015 immunization stakeholders in Nigeria were proceeding with plans that would have fielded two nationally representative surveys to estimate vaccination coverage at the same time. Rather than duplicate efforts and generate either conflicting or redundant results, the stakeholders collaborated to conduct a combined Multiple Indicator Cluster Survey (MICS) / National Immunization Coverage Survey (NICS) with MICS focusing on core sampling clusters and NICS adding supplementary clusters in 20 states, to improve precision of outcomes there. This paper describes the organizational and technical aspects of that collaboration, including details on design of the sample supplement and analysis of the pooled dataset. While complicated, the collaboration was successful; it yielded a unified set of relevant coverage estimates and fostered some novel sub-national results dissemination work.

Immunization Coverage Surveys and Linked Biomarker Serosurveys in Three Regions in Ethiopia.

OBJECTIVE: Demographic and health surveys, immunization coverage surveys and administrative data often divergently estimate vaccination coverage, which hinders pinpointing districts where immunization services require strengthening. We assayed vaccination coverage in three regions in Ethiopia by coverage surveys and linked serosurveys. METHODS: Households with children aged 12-23 (N = 300) or 6-8 months (N = 100) in each of three districts (woredas) were randomly selected for immunization coverage surveys (inspection of vaccination cards and immunization clinic records and maternal recall) and linked serosurveys. IgG-ELISA serologic biomarkers included tetanus antitoxin ≥ 0.15 IU/ml in toddlers (receipt of tetanus toxoid) and Haemophilus influenzae type b (Hib) anti-capsular titers ≥ 1.0 mcg/ml in infants (timely receipt of Hib vaccine). FINDINGS: Coverage surveys enrolled 1,181 children across three woredas; 1,023 (87%) also enrolled in linked serosurveys. Administrative data over-estimated coverage compared to surveys, while maternal recall was unreliable. Serologic biomarkers documented a hierarchy among the districts. Biomarker measurement in infants provided insight on timeliness of vaccination not deducible from toddler results. CONCLUSION: Neither administrative projections, vaccination card or EPI register inspections, nor parental recall, substitute for objective serological biomarker measurement. Including infants in serosurveys informs on vaccination timeliness.

Strategies for Coordination of a Serosurvey in Parallel with an Immunization Coverage Survey.

A community-based immunization coverage survey is the standard way to estimate effective vaccination delivery to a target population in a region. Accompanying serosurveys can provide objective measures of protective immunity against vaccine-preventable diseases but pose considerable challenges with respect to specimen collection and preservation and community compliance. We performed serosurveys coupled to immunization coverage surveys in three administrative districts (woredas) in rural Ethiopia. Critical to the success of this effort were serosurvey equipment and supplies, team composition, and tight coordination with the coverage survey. Application of these techniques to future studies may foster more widespread use of serosurveys to derive more objective assessments of vaccine-derived seroprotection and monitor and compare the performance of immunization services in different districts of a country.

Drivers of routine immunization coverage improvement in Africa: findings from district-level case studies.

There is limited understanding of why routine immunization (RI) coverage improves in some settings in Africa and not in others. Using a grounded theory approach, we conducted in-depth case studies to understand pathways to coverage improvement by comparing immunization programme experience in 12 districts in three countries (Ethiopia, Cameroon and Ghana). Drawing on positive deviance or assets model techniques we compared the experience of districts where diphtheria-tetanus-pertussis (DTP3)/pentavalent3 (Penta3) coverage improved with districts where DTP3/Penta3 coverage remained unchanged (or steady) over the same period, focusing on basic readiness to deliver immunization services and drivers of coverage improvement. The results informed a model for immunization coverage improvement that emphasizes the dynamics of immunization systems at district level. In all districts, whether improving or steady, we found that a set of basic RI system resources were in place from 2006 to 2010 and did not observe major differences in infrastructure. We found that the differences in coverage trends were due to factors other than basic RI system capacity or service readiness. We identified six common drivers of RI coverage performance improvement-four direct drivers and two enabling drivers-that were present in well-performing districts and weaker or absent in steady coverage districts, and map the pathways from driver to improved supply, demand and coverage. Findings emphasize the critical role of implementation strategies and the need for locally skilled managers that are capable of tailoring strategies to specific settings and community needs. The case studies are unique in their focus on the positive drivers of change and the identification of pathways to coverage improvement, an approach that should be considered in future studies and routine assessments of district-level immunization system performance.

Integrated delivery of health services during outreach visits: a literature review of program experience through a routine immunization lens.

BACKGROUND: Outreach services are used systematically to deliver immunization and health services to individuals with insufficient access to health facilities in lower-income countries. Currently, the topic of integrated service delivery during immunization outreach lacks the attention paid to integration at fixed sites or during campaigns. This article explores integrated outreach and risks associated with service integration. METHODS: Published and gray literature in public health databases and on organization websites were reviewed, yielding 33 articles and gray literature documents for a literature review of experience integrating other services with routine immunization at outreach sessions. RESULTS: The current policy climate favors service integration as a strategy for increasing the equity and efficiency of important health interventions. However, integration may also present some risk to well-established and resourced interventions, such as immunization, which must be recognized as programs compete for limited resources. Experience reveals integration opportunities in planning and intersectoral coordination, training and supervision, community participation, pooled funding, and monitoring. CONCLUSIONS: The reviewed literature indicates that successful integration of health interventions with immunization at routine outreach sessions requires well-planned and implemented steps. It also highlights the need for additional studies or feedback on planning and implementing integrated outreach services in lower-income countries.