Burden of incomplete immunization and its determinants among children under five years in India: a systematic review and meta-analysis (2015-2025).

BACKGROUND

Despite substantial improvements in childhood vaccination coverage under India's Universal Immunization Programme (UIP) and initiatives such as Mission Indradhanush, incomplete immunization remains a significant public health challenge. This systematic review and meta-analysis aimed to estimate the pooled prevalence of incomplete immunization among children under five years in India and identify its major determinants.

METHODS

A systematic search of PubMed/MEDLINE, Scopus, Web of Science, Embase, Cochrane Library, Google Scholar, IndMed, and grey literature was conducted for studies published between January 2015 and December 2025. Observational studies reporting prevalence and/or determinants of incomplete immunization among children aged 0-59 months in India were included. Random-effects meta-analysis with Hartung-Knapp-Sidik-Jonkman adjustment was performed. Heterogeneity was assessed using the I2 statistic, while publication bias was evaluated using contour-enhanced funnel plots, Egger's regression test, and Begg's rank correlation test.

RESULTS

Forty-five cross-sectional studies involving more than 428,000 participants were included. The pooled prevalence of incomplete immunization was 26% (95% CI: 21%-32%), with substantial heterogeneity (I2 = 99.9%). Higher prevalence was observed in northern and multistate studies compared with southern and northeastern regions. Significant determinants of incomplete immunization included absence of an immunization card (OR 9.46, 95% CI: 3.28-27.28), non-institutional delivery (OR 3.59, 95% CI: 1.96-6.56), maternal illiteracy (OR 3.25, 95% CI: 2.22-4.78), low socioeconomic status (OR 2.03, 95% CI: 1.51-2.71), higher birth order (OR 1.88, 95% CI: 1.17-3.03), and female gender (OR 1.34, 95% CI: 1.06-1.69). Sensitivity analyses confirmed robustness of findings.

CONCLUSIONS

Approximately one in four children in India remains incompletely immunized. Persistent socioeconomic, maternal, and healthcare access barriers contribute substantially to inequities in vaccination coverage. Strengthening institutional delivery, maternal education, immunization tracking systems, and targeted outreach for vulnerable populations is essential to achieve Immunization Agenda 2030 targets in India.