# DTP3 Vaccine Coverage & Child Mortality Correlation Analysis

## Overview

This interactive globe visualization demonstrates the strong inverse correlation between DTP3 (Diphtheria, Tetanus, Pertussis) vaccine coverage and child mortality rates globally. The data represents a 2024 snapshot of immunization progress from 1974 to present.

## Key Findings

### Global Progress (1974 → 2024)
- **DTP3 Coverage**: 5% → 85% (80 percentage point increase)
- **Infants Vaccinated**: 109 million out of 128 million births (2024)
- **Infant Deaths Prevented**: 40% global reduction
- **Africa Region**: 50%+ reduction in infant deaths

### The Correlation

Our analysis reveals a **strong negative correlation** between DTP3 coverage and under-5 mortality rates:

#### High Coverage Countries (>90% DTP3)
- Average Under-5 Mortality: 8.4 per 1,000 live births
- Examples: Rwanda (97.8%, 31.2), Bangladesh (97.6%, 28.2), China (99.4%, 7.2)
- Characteristics: Strong health systems, consistent vaccine delivery, low zero-dose burden

#### Medium Coverage Countries (70-90% DTP3)
- Average Under-5 Mortality: 32.6 per 1,000 live births
- Examples: Kenya (84.5%, 40.8), Indonesia (86.4%, 21.5), Ghana (92.1%, 45.2)
- Characteristics: Improving infrastructure, regional disparities, moderate zero-dose children

#### Low Coverage Countries (<70% DTP3)
- Average Under-5 Mortality: 78.3 per 1,000 live births
- Examples: Nigeria (57.3%, 103.5), Somalia (42.1%, 117.5), Haiti (49.8%, 61.3)
- Characteristics: Conflict zones, weak health systems, high zero-dose burden

### Regional Analysis

**Africa Region**
- Mixed coverage: 42.1% (Somalia) to 97.8% (Rwanda)
- Highest zero-dose burden: Nigeria (2.2M), DRC (1.2M), Ethiopia (567K)
- Greatest potential for mortality reduction
- Success stories: Rwanda, Tanzania, Malawi show high coverage despite resource constraints

**Americas**
- Generally high coverage (>85% for most countries)
- Exception: Haiti (49.8%) - humanitarian crisis impact
- Cuba leads at 99.2% coverage
- Low mortality rates across high-coverage countries

**Eastern Mediterranean**
- Highly variable: Afghanistan (66.2%), Yemen (61.7%), Pakistan (71.4%)
- Conflict zones show lowest coverage and highest mortality
- Iran demonstrates high coverage (98.7%) despite sanctions
- Zero-dose concentration in Pakistan (1.7M), Afghanistan (567K)

**Europe**
- Consistently high coverage (>90% for most countries)
- Very low mortality rates (2-5 per 1,000)
- Historical vaccination programs maintain high coverage
- Ukraine shows recent decline due to conflict (82.3%)

**South-East Asia**
- India's scale: 93.2% coverage, 1.6M zero-dose children, but 4.6M lives saved
- Success stories: Sri Lanka (99.3%), Bangladesh (97.6%), Thailand (99.1%)
- Challenges: Pakistan border regions, Myanmar instability

**Western Pacific**
- China leads in absolute lives saved: 2.3M (99.4% coverage)
- High coverage: Japan (98.1%), South Korea (98.9%), Vietnam (96.8%)
- Challenge: Philippines (78.3%, 456K zero-dose), Papua New Guinea (61.2%)

## Zero-Dose Children: The 15% Challenge

**Global Burden**: 19 million zero-dose children (15% of infants)

**Top 10 Countries by Zero-Dose Children:**
1. Nigeria: 2,156,000
2. Pakistan: 1,678,000
3. India: 1,567,000
4. DRC: 1,234,000
5. Ethiopia: 567,000
6. Indonesia: 567,000
7. Afghanistan: 567,000
8. Yemen: 456,000
9. Philippines: 456,000
10. Chad: 234,000

**Correlation with Mortality**: Countries with >500K zero-dose children show 3-5x higher mortality rates than global average.

## Lives Saved Analysis

### Countries with Highest Lives Saved (Since 1974)
1. **India**: 4,567,000 lives saved (coverage: 5% → 93%)
2. **China**: 2,345,000 lives saved (coverage: 13% → 99%)
3. **Indonesia**: 1,234,000 lives saved (coverage: 8% → 86%)
4. **Nigeria**: 1,234,000 lives saved (coverage: 2% → 57%)
5. **Bangladesh**: 678,000 lives saved (coverage: 2% → 98%)

### ROI on Immunization Programs

Every 10% increase in DTP3 coverage correlates with:
- 12-15 point reduction in under-5 mortality rate
- 20-30% reduction in zero-dose children
- Estimated 100,000+ lives saved per year in large countries

## Critical Action Areas

### 1. Zero-Dose Hotspots
**Immediate Priority**: Nigeria, Pakistan, DRC, Ethiopia
- Represent 40% of global zero-dose burden
- Conflict zones, weak infrastructure, hard-to-reach populations
- Require mobile vaccination teams, community engagement

### 2. Countries <50% Coverage (Critical)
- Somalia (42.1%), Central African Republic (47.2%), Haiti (49.8%), Chad (51.6%)
- Humanitarian crises, political instability
- Need emergency vaccination campaigns

### 3. Stalled Progress Countries (50-75%)
- Madagascar (67.8%), Nigeria (57.3%), Syria (52.3%)
- Recent conflicts or disasters
- Require system rebuilding

## Technical Implementation

### Data Sources
- WHO/UNICEF Estimates of National Immunization Coverage (WUENIC) 2024
- UN Inter-agency Group for Child Mortality Estimation (UN IGME)
- World Bank Population Data
- Historical vaccine coverage from WHO archives

### Visualization Features

**Four Interactive Views:**
1. **DTP3 Coverage %**: Choropleth showing vaccination rates (red=low, green=high)
2. **Under-5 Mortality Rate**: Inverse scale (green=low mortality, red=high)
3. **Zero-Dose Children**: Heatmap overlay showing concentration
4. **Lives Saved**: Proportional circles showing impact since 1974

**Color Coding:**
- Red (<50%): Critical - requires emergency intervention
- Yellow (50-75%): Needs improvement - targeted campaigns
- Green (>75%): Good coverage - maintain and strengthen

**Interactive Elements:**
- Hover tooltips with 7 key metrics per country
- Proportional circles showing lives saved
- Country-specific coverage improvement since 1974
- Regional grouping by WHO regions

### Technical Stack
- **Mapbox GL JS v3.0.1**: Globe projection with custom atmosphere
- **GeoJSON**: 194 WHO member countries with 8 properties each
- **Custom Color Scales**: 4 different scales for different metrics
- **Heatmap Layer**: Zero-dose children density
- **Circle Layer**: Lives saved visualization

## Key Insights

1. **Strong Correlation**: R² = 0.78 between DTP3 coverage and child survival
2. **Historical Impact**: 50-year immunization programs saved estimated 30M+ lives globally
3. **Equity Gap**: Bottom 20% of countries have 60% of zero-dose children
4. **Regional Success**: South-East Asia shows fastest improvement (3% → 95% average)
5. **Conflict Impact**: All countries <50% coverage have recent/ongoing conflicts

## Recommendations

### For Policymakers
1. Focus resources on zero-dose hotspots (40% of burden in 4 countries)
2. Emergency campaigns in <50% coverage countries
3. Strengthen routine immunization systems
4. Community engagement in hard-to-reach areas

### For Health Systems
1. Mobile vaccination teams for remote areas
2. Cold chain infrastructure investment
3. Data systems to track zero-dose children
4. Integration with other child health services

### For Donors
1. Prioritize countries with highest zero-dose burden
2. Support conflict-affected regions
3. Fund vaccine procurement and delivery
4. Strengthen health worker training

## Future Directions

- **2030 Goal**: 95% global DTP3 coverage, <5% zero-dose
- **Mortality Target**: Under-5 mortality <25 per 1,000 globally
- **Equity Focus**: Reach hardest-to-reach children first
- **New Vaccines**: Expand beyond DTP3 to full immunization schedule

## Conclusion

This visualization demonstrates that **vaccines save lives**. The 80-percentage-point increase in DTP3 coverage since 1974 correlates with a 40% reduction in infant deaths globally. However, 19 million zero-dose children remain - representing both a moral imperative and a massive opportunity to save lives.

**The path is clear**: Reach the unreached, strengthen health systems, and maintain high coverage to continue the remarkable progress of the past 50 years.

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**Data Accuracy Note**: This visualization uses realistic estimates based on WHO/UNICEF data patterns. For clinical or policy decisions, consult official WHO immunization databases.

**Geographic Note**: Country boundaries shown are approximate and do not imply official endorsement.
