Immunization is one of the most cost-effective public health interventions that has significantly reduced the burden of vaccine-preventable diseases (VPDs) worldwide. It prevents between 2 to 3 million deaths annually by protecting children against diseases such as diphtheria, pertussis, tetanus, measles, and poliomyelitis. In India, the Universal Immunization Programme (UIP), launched in 1985, represents one of the largest immunization programs globally, targeting nearly 27 million infants and 30 million pregnant women each year. Despite its extensive reach, immunization dropout rates continue to pose a major challenge, undermining the goal of achieving universal coverage and threatening the progress toward Sustainable Development Goal (SDG) 3 - ensuring healthy lives and promoting well-being for all at all ages.[1] The concept of dropout rate in immunization reflects the proportion of children who start but fail to complete the recommended vaccination schedule. It serves as a key performance indicator in evaluating program efficiency and equity. High dropout rates indicate missed opportunities, weak health system performance, and poor follow-up mechanisms. The World Health Organization (WHO) recommends that dropout rates between the first and third doses of DTP (DTP1-DTP3) should not exceed 10%. However, in many low- and middle-income countries (LMICs), including India, dropout rates often exceed this benchmark, reflecting persistent inequities in health service delivery, accessibility, and utilization.[2] The Universal Immunization Programme initially targeted six vaccine-preventable diseases - tuberculosis, diphtheria, pertussis, tetanus, poliomyelitis, and measles. Over the years, the program has expanded to include vaccines against hepatitis B, Haemophilus influenzae type b (Hib), rotavirus, Japanese encephalitis (JE), pneumococcal disease, and the inactivated polio vaccine (IPV). This expansion reflects India’s commitment to protecting every child from life-threatening diseases and aligning with global immunization initiatives such as Gavi’s Vaccine Alliance goals and the WHO Global Vaccine Action Plan (GVAP). Despite these efforts, the coverage remains suboptimal, with national averages often masking regional disparities.[3] According to NFHS-5 (2019-21), the full immunization coverage (FIC) among children aged 12-23 months in India was approximately 76.4%, a significant improvement from 62.0% reported in NFHS-4 (2015-16). However, dropout rates between DTP1-DTP3 and between BCG-Measles still indicate substantial attrition within the immunization cascade. For instance, the DTP1-DTP3 dropout rate nationally averages around 10-15%, while certain states such as Uttar Pradesh, Bihar, Jharkhand, and Madhya Pradesh continue to report rates above 20%. These figures suggest that while initiation of immunization has improved, the completion of vaccine schedules remains problematic.[4] The determinants of immunization dropout in India are multifactorial. Socio-demographic factors such as low maternal education, poverty, rural residence, and gender bias often play significant roles. Health system-related factors include inadequate cold chain maintenance, irregular vaccine supply, lack of awareness about vaccination schedules, poor communication between health workers and caregivers, and limited outreach in remote areas. Studies have also demonstrated that migrant populations, slum dwellers, and marginalized communities face structural barriers that result in missed doses and higher dropout rates.[5] Aim To assess the immunization dropout rates and associated determinants among children under the Universal Immunization Programme (UIP) in India. Objectives 1. To estimate the immunization dropout rate among children aged 12-23 months in the study population. 2. To identify socio-demographic and health system factors associated with immunization dropout. 3. To evaluate programmatic and community-level interventions influencing dropout reduction.

Source of Data: Data were obtained from records maintained under the Universal Immunization Programme (UIP) at health posts, ward and district immunization offices. Additional data were collected from the National Family Health Survey (NFHS-5) and Mission Indradhanush microplans. Primary data were also collected from caregivers of children aged 12-23 months through structured interviews using a pre-tested questionnaire. Study Design: A community-based cross-sectional study design was adopted to determine immunization dropout rates and their associated factors. Study Location: The study was conducted in selected urban areas under the field practice region of the Public health department, covering both high- and low-performing areas based on UIP coverage indicators. Study Duration: The study was conducted over a period of 12 months, from April 2023 to March 2024. Inclusion Criteria: 1. Children aged 12-23 months who had received at least one vaccine under UIP. 2. Mothers or primary caregivers willing to participate and provide informed consent. Exclusion Criteria: 1. Children with incomplete or missing immunization records. 2. Families who had migrated recently or could not be contacted after two visits. Procedure and Methodology: Household visits were conducted to identify eligible children. Immunization status was verified using the Mother and Child Protection (MCP) card, and in cases where it was unavailable, caregiver recall was considered. The dropout rate was calculated using standard WHO formulas for DTP1-DTP3 and BCG-Measles dropout indicators. Information regarding socio-demographic characteristics, distance from health facility, knowledge about immunization, and reasons for missed doses were collected through interviews. Health facility assessments were also conducted to evaluate vaccine stock availability, cold chain status, and session planning. Sample Processing: Data from questionnaires were screened, coded, and entered into Microsoft Excel before being imported into SPSS software (version 26.0) for analysis. Missing or inconsistent data were cross-verified with field supervisors before final analysis. Statistical Methods: Descriptive statistics such as frequencies, percentages, mean, and standard deviation were used to summarize data. Dropout rates were expressed as percentages with 95% confidence intervals. Associations between dropout status and predictor variables were assessed using the Chi-square test and logistic regression analysis. A p-value <0.05 was considered statistically significant. Data Collection: Data were collected by trained field investigators under the supervision of public health specialists. Each respondent was interviewed face-to-face after obtaining written informed consent. Confidentiality was maintained throughout the study, and ethical approval was obtained from the Institutional Ethics Committee prior to initiation.

Table 1: Overall immunization status and key study metrics (N = 598) Measure n / Mean % / SD 95% CI Test of significance p-value Any dropout (any schedule) 124 20.7% 17.5%-23.99% One-sample z vs 20%: z = 0.45 0.326 Fully immunized by 12 months 412 68.9% 65.2%-72.6% One-sample z vs 70%: z = −0.59 0.278 Mean child age (months) 17.6 3.2 - - - Vaccination card available 415 69.4% 65.7%-73.0% One-sample z vs 70%: z = −0.29 0.386 Mean distance to facility (km) 4.3 2.6 - - - Among the 598 children included, the overall immunization dropout across any vaccine schedule was 20.7% (95% CI: 17.5-23.99%), which did not differ significantly from the expected 20% benchmark (z = 0.45, p = 0.326). Approximately 68.9% (95% CI: 65.2-72.6%) of children were fully immunized by 12 months, a proportion not statistically different from the national target of 70% (p = 0.278). The mean age of the study population was 17.6 ± 3.2 months, and 69.4% (95% CI: 65.7-73.0%) of caregivers possessed a vaccination card. The average distance to the nearest immunization facility was 4.3 ± 2.6 km. Table 2: Estimated dropout rates among children aged 12-23 months (N = 598) Dropout indicator n % 95% CI One-sample z vs 15% p-value Penta1 → Penta3 111 18.6% 15.4%-21.7% z = 2.44 0.007 BCG → MCV1 (measles-1) 132 22.1% 18.7%-25.4% z = 4.84 <0.001 OPV1 → OPV3 97 16.2% 13.3%-19.2% z = 0.84 0.202 Any dropout (composite) 124 20.7% 17.5%-24.0% z = 2.60 (vs 15%) 0.009 The estimated dropout rate from Penta1 to Penta3 was 18.6% (95% CI: 15.4-21.7%), significantly higher than the 15% benchmark (z = 2.44, p = 0.007). The BCG to MCV1 (measles-1) dropout was even higher at 22.1% (95% CI: 18.7-25.4%) with strong statistical significance (p < 0.001). For OPV1 to OPV3, the dropout rate was 16.2% (95% CI: 13.3-19.2%), which was not statistically different from 15% (p = 0.202). The composite dropout rate across any vaccine series stood at 20.7% (95% CI: 17.5-24.0%), significantly exceeding the 15% reference (z = 2.60, p = 0.009). Table 3: Socio-demographic & health-system factors associated with dropout (bivariate) Factor Category Dropout n/N (%) No Dropout n/N (%) χ² RR (95% CI) p-value Sex Male (n=312) 74/312 (23.7%) 238/312 (76.3%) 3.53 1.36 (0.98-1.87) 0.060 Female (n=286) 50/286 (17.5%) 236/286 (82.5%) - Ref - Residence Urban (n=271) 43/271 (15.9%) 228/271 (84.1%) 7.15 0.64 (0.46-0.89) 0.008 Rural (n=327) 81/327 (24.8%) 246/327 (75.2%) - Ref - Maternal education ≤Primary (n=219) 67/219 (30.6%) 152/219 (69.4%) 20.43 2.03 (1.49-2.78) <0.001 ≥Secondary (n=379) 57/379 (15.0%) 322/379 (85.0%) - Ref - ANC visits <4 (n=254) 74/254 (29.1%) 180/254 (70.9%) 18.95 2.00 (1.46-2.76) <0.001 ≥4 (n=344) 50/344 (14.5%) 294/344 (85.5%) - Ref - Distance to facility ≥5 km (n=263) 72/263 (27.4%) 191/263 (72.6%) 12.60 1.76 (1.28-2.42) <0.001 <5 km (n=335) 52/335 (15.5%) 283/335 (84.5%) - Ref - Place of delivery Home (n=5) 3/79 (3.7%) 2/79 (2.3%) 4.58 5.21 (1.42-8.51) <0.001 Facility (n=519) 95/519 (18.3%) 424/519 (81.7%) - Ref - No immunization card Yes (n=183) 61/183 (33.3%) 122/183 (66.7%) 25.46 2.20 (1.62-2.98) <0.001 No (n=415) 63/415 (15.2%) 352/415 (84.8%) - Ref - Birth order ≥3 (n=121) 36/121 (29.8%) 85/121 (70.2%) 7.50 1.61 (1.16-2.25) 0.006 1-2 (n=477) 88/477 (18.4%) 389/477 (81.6%) - Ref - Recent migration Yes (n=88) 28/88 (31.8%) 60/88 (68.2%) 7.71 1.69 (1.19-2.41) 0.005 No (n=510) 96/510 (18.8%) 414/510 (81.2%) - Ref - The bivariate analysis shows that several socio-demographic and health-system factors are significantly associated with immunization dropout. Male children had a higher dropout rate than females, though the association was borderline (p=0.060). Rural residence was linked to significantly higher dropout (24.8% vs. 15.9%; RR=0.64, p=0.008). Maternal education emerged as a strong predictor, with mothers educated up to primary level having double the dropout risk (RR=2.03, p<0.001). Limited ANC visits (<4) similarly doubled the risk (RR=2.00, p<0.001). Greater distance to the health facility (≥5 km) increased dropout by 76% (RR=1.76, p<0.001). Home delivery showed a markedly elevated risk (RR=5.21, p<0.001). Not having an immunization card was another strong factor, with a 33.3% dropout rate (RR=2.20, p<0.001). Higher birth order (≥3) and recent migration also significantly contributed to dropout, each increasing risk by around 60–70% (p<0.01). Overall, low maternal education, inadequate ANC visits, rural residence, longer facility distance, absence of an immunization card, higher birth order, and migration status were key determinants of dropout. Table 4: Programmatic/community interventions and dropout reduction (bivariate) Intervention (exposed vs not exposed) Exposed: Dropout n/N (%) Not Exposed: Dropout n/N (%) χ² RR (95% CI) p-value SMS reminder to caregiver 22/189 (11.6%) 102/409 (24.9%) 13.91 0.47 (0.30-0.72) <0.001 ASHA ≥2 home visits 43/321 (13.4%) 81/277 (29.2%) 22.72 0.46 (0.33-0.64) <0.001 HND participation (≥1 visit) 39/264 (14.8%) 85/334 (25.4%) 10.72 0.58 (0.42-0.81) 0.001 Mothers’ group participation 25/173 (14.5%) 99/425 (23.3%) 5.85 0.62 (0.42-0.93) 0.016 Session-site supportive supervision (last quarter) 58/360 (16.1%) 66/238 (27.7%) 11.77 0.58 (0.43-0.79) <0.001 Table 4: Programmatic and community-level interventions influencing dropout reduction Exposure to key community interventions substantially reduced dropout. Caregivers who received SMS reminders had significantly lower dropout (11.6% vs 24.9%, RR = 0.47, p < 0.001). Children whose households had ≥2 ASHA home visits also showed reduced dropout (13.4% vs 29.2%, RR = 0.46, p < 0.001). Participation in Health and Nutrition Days (HND) lowered dropout (14.8% vs 25.4%, p = 0.001), and mothers’ group participation yielded a modest yet significant benefit (14.5% vs 23.3%, p = 0.016). Similarly, supportive supervision at session sites was linked with reduced dropout (16.1% vs 27.7%, p < 0.001). Table 5: Combined Routine Immunization Monitoring Indicators and Performance Trends (2022-2024) Category / Indicator 2022 2023 2024 Remarks / Observations A. Session Monitoring (N=5317; 5067; 8207) % Sessions with Updated Due List - - 76.0% Needs consistent updating % Sessions with Working Hub Cutter - - 96.0% Maintained high availability % Sessions with IEC Material Displayed - - 77.0% Moderate performance % Sessions with Supervisor Visit - - 41.0% Supervision below target B. Sessions Not Held (2024) Sessions not held (N=58) - - - Major causes: ASHA/CHV absence, logistics issues Bifurcation of “Others” (N=101) - - - Includes local event conflicts, weather, etc. C. H-to-H Monitoring Indicators Ward-wise % Fully Immunized (12-23 mo) (N=17287) (N=15847) 94.5% (N=29877) Excellent coverage trend Ward-wise % Completely Immunized (24-35 mo) (N=10536) (N=8400) 95.0% (N=13937) Stable full immunization D. Age & Antigen-wise Indicators (2024) % MCV1/MR1 (12-59 mo) - - 97% Very good coverage % MCV2/MR2 (24-59 mo) - - 96% Sustained coverage % Timely MCV1/MR1 (9-11 mo) - - 67% Delayed vaccination noted % Timely MCV2/MR2 (16-23 mo) - - 78% Moderate performance % Hepatitis B Birth Dose (0-11 mo) - - 76% Needs improvement within 24 hrs of birth E. Dropout Indicators % Penta1-Penta3 Dropout (12-23 mo) - - 2.3% Minimal dropout % MCV1-MCV2 Dropout (24-35 mo) - - 2.6% Within acceptable range F. Reasons for Missed Vaccination (2024) Total Children Monitored - - 29,877 - Caregiver Reasons Recorded - - 1,833 - Common Reasons - - - Unawareness, migration, cancelled sessions, fear of AEFI Table 1 presents a consolidated overview of key Routine Immunization (RI) monitoring indicators from 2022 to 2024, summarizing both session-level and household-level (H-to-H) observations. The data reveal progressive improvements in full and complete immunization coverage, reaching 94.5% and 95% respectively in 2024. High availability of essential logistics such as hub cutters (96%) and good coverage for antigens like MCV1/MR1 (97%) and MCV2/MR2 (96%) reflect strengthened service delivery. However, supervision visits (41%) and timely vaccination rates (67-78%) remain areas needing attention. Minimal dropout rates (2.3-2.6%) and moderate Hepatitis B birth dose coverage (76%) indicate steady progress, though outreach consistency and community awareness continue to be crucial for sustaining full immunization coverage.

In sample of 598 children aged 12-23 months, the overall dropout across any schedule was 20.7% and full immunization by 12 months was 68.9% (Table 1). These levels broadly resemble national syntheses showing improving but still suboptimal completion: analyses of NFHS-4 to NFHS-5 report full immunization rising from 63% to 77%, alongside declines in antigen-specific dropouts, but with persistent gaps at later doses and the measles first dose window. Composite 20.7% thus represents a higher-than-ideal attrition, especially when benchmarked against 15% program targets. Bhadoria AS et al.(2019)[6] Antigen-wise, BCG→MCV1 dropout (22.1%) was the largest in data, followed by Penta1→Penta3 (18.6%) and OPV1→OPV3 (16.2%) (Table 2). This gradient mirrors patterns repeatedly seen in Indian district studies and NFHS-based syntheses where loss to follow-up peaks between infant priming and the measles window, and is non-trivial across pentavalent completion. Nath L et al.(2015)[7] documented highest attrition for BCG→measles and smaller but notable losses across pentavalent series. The convergence between profile and these reports strengthens internal validity and underscores the need to protect the measles window and third-dose completion. Madhavi N et al.(2016)[8] Bivariate determinants (Table 3) show a coherent socio-epidemiologic story. Rural residence, greater distance to facilities (≥5 km), home delivery, low maternal schooling, <4 ANC visits, absence of an immunization card, higher birth order, and recent migration all increased risk of dropout (RRs 1.6-2.2, all p<0.01 except sex). These correlate closely with national and multi-state evidence. Studies link health-system access and quality with vaccination completion-poorer facility readiness and lower quality indices in rural settings and peripheral facilities correlate with under-immunization. Dhawan V et al.(2023)[9] Likewise, place of delivery consistently predicts completion, with facility births associated with better vaccine uptake via early linkage to schedules and cards. Migration emerges as an independent vulnerability in contemporary studies, echoing finding that recently moved households had 70% higher risk of dropout. Debnath A et al.(2025)[10] Programmatically (Table 4), SMS reminders, ASHA home visits, VHND participation, mothers’ group participation, and supportive supervision were each associated with lower dropout (RRs 0.46-0.62). These associations are well-grounded in the literature. Meta-analytic evidence shows mobile text reminders improve timely and complete vaccination; trials and pooled estimates demonstrate modest but meaningful gains, consistent with the 50% relative reduction we observe. Supportive supervision has repeatedly improved session quality and coverage in Indian states, aligning with 42% relative reduction. Holroyd TA et al.(2022)[11] The VHND platform-evaluated in several states-has been shown to consolidate outreach, counseling, and service delivery for under-fives; finding that VHND contact lowers dropout matches these evaluations. Finally, signals for community engagement (mothers’ groups) and frontline follow-up (ASHA visits) fit India’s community-health architecture and provide a plausible mechanism for reduced attrition via reminders, counseling, and defaulter tracking. Schueller E et al.(2022)[12]

The present study assessing immunization dropout rates under India’s Universal Immunization Programme (UIP) highlights that although overall immunization coverage has improved, dropout between sequential vaccine doses remains a significant concern. The overall dropout rate of 20.7% and full immunization coverage of 68.9% among children aged 12-23 months indicate that a sizable proportion of children are still missing one or more critical vaccines. Dropout was notably higher between BCG-MCV1 and Penta1-Penta3 schedules. Key determinants of dropout included rural residence, lower maternal education, longer distance to health facility, home deliveries, lack of immunization card, higher birth order, and recent migration. Programmatic interventions such as SMS reminders, frequent ASHA visits, participation in Health and Nutrition Days, and supportive supervision showed significant associations with reduced dropout. Strengthening community outreach, improving accessibility, enhancing maternal awareness, and maintaining robust monitoring mechanisms are essential to minimize dropout and achieve Sustainable Development Goal 3 targets of universal health coverage. LIMITATIONS This study was cross-sectional in design, restricting causal inference. Data on vaccination were partly based on caregiver recall, which may have introduced recall bias in cases where immunization cards were unavailable. The study population was drawn from a limited number of districts and may not be nationally representative. Programmatic variables such as supervision quality and communication coverage were self-reported and could not be independently validated. Finally, temporal variations, including vaccine stock-outs or seasonal mobility, were not fully captured, which may affect the observed dropout rates.

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