Progress in reaching zero-dose children: analysis of population-modifiable risk factors and inequity trends in low- and lower-middle-income countries.

Abstract

Background: Zero-dose (ZD) children remain concentrated in low- and lower-middle-income countries (LLMICs) and are a major focus of the Immunization Agenda 2030 (IA2030), which aims to halve their number by 2030. Despite this commitment, progress has stalled in many high-burden settings. This study aimed to examine progress in reaching ZD children, trends in wealth-related inequity, and key population-modifiable risk factors across LLMICs over the past decade.

Methods: We analysed two rounds of the most recent Demographic and health survey (DHS) datasets from ten LLMICs to assess progress in reducing the number of ZD children. Countries were included based on the availability of post-2020 survey rounds. ZD children were defined as children aged 12-23 months who had not received any dose of BCG, DTP-containing, polio, or measles-containing vaccines. The concentration index was used to assess wealth-related inequities. Multilevel logistic regression models were used to identify modifiable risk factors associated with ZD status. The population attributable fraction (PAF) was calculated using odds ratios and prevalence estimates to quantify the contribution of modifiable risk factors.

Results: ZD prevalence increased significantly in five of ten countries - Mozambique (4.8% to 14.2%), Côte d'Ivoire (4.9% to 8.7%), Nepal (0.8% to 4.5%), Tanzania (2.3% to 4.4%), and Madagascar (13.3% to 18.1%) - while no statistically significant change was observed in the remaining five. Wealth-related inequities were significant in most countries, with ZD children disproportionately concentrated in the poorest households. Home delivery had the highest PAF for ZD (17.1%; 95% CI: 14.1-19.6), followed by fewer than four ANC contacts (8.6%; 95% CI: 7.2-10.0) and non-use of contraceptives (6.9%; 95% CI: 5.3-8.5). The combined contribution of reproductive and maternal health services was (PAF = 29.4%; 95% CI: 24.5-33.7). Socioeconomic factors included lack of maternal education (4.4%; 95% CI: 2.6-6.1) and not listening to the radio (2.7%; 95% CI: 0.4-4.6).

Conclusion: Progress in reaching ZD children in low- and lower-middle-income countries has declined. A renewed commitment and continued effort are needed to reach ZD children in these regions by improving access to health services and addressing the socioeconomic challenges of families.