Vaccination Coverage Assessment

Vaccination Coverage - Shielding the Masses

• Definition: Proportion of a defined population (e.g., infants, pregnant women) that has received a specific vaccine or all doses in a schedule.
• Goal: Achieve high & equitable coverage (typically >90% for Universal Immunization Programme vaccines) to interrupt disease transmission.
• Importance:
  • Direct protection for vaccinated individuals.
  • Indirect protection for the community via Herd Immunity.
    • Occurs when a critical portion of a community is immunized against a contagious disease, protecting unimmunized individuals.
    • Herd Immunity Threshold: $p_c = 1 - 1/R_0$ (where $R_0$ = Basic Reproduction Number).
    • Example: Measles requires >90-95% coverage for effective herd immunity.

⭐ The minimum level of immunization coverage needed to achieve herd immunity varies by disease; for measles, it is one of the highest at >90-95% due to its high infectivity ($R_0$ of 12-18).

Assessment Methods - Counting the Shots

Primary method for field assessment:

• WHO 30x7 Cluster Sampling: Standard for rapid coverage estimation.
  • Objective: Estimate coverage for individual vaccines (BCG, OPV, DPT, Measles, Hepatitis B) & full immunization status.
  • Sample: 30 clusters (villages/wards) × 7 children per cluster = 210 children.
  • Target Age: Typically 12-23 months (assesses timely completion of primary series).
  • Cluster Selection: Probability Proportional to Size (PPS) from a complete sampling frame.
  • Household Selection:
    • Randomly select first household in a cluster.
    • Proceed to nearest households until 7 eligible children are found.
  • Data Sources: Vaccination cards (primary), mother's reliable recall (secondary).

⭐ The 30x7 cluster sampling method, widely used by WHO, typically provides coverage estimates with a precision of ±10% at a 95% confidence level for the entire sampled area.

Indicators & Interpretation - Reading the Report Card

| | Dropout Rate (DOR) | % children starting but not completing multi-dose series (e.g., DPT1 to DPT3). | $((Initial\ Dose\ - \ Final\ Dose) / Initial\ Dose) * 100## Indicators & Interpretation - Reading the Report Card

. Target: <10%. | | Invalid Doses | Doses given too early, too late, wrong interval/route. Reduces true protection. | Not counted in coverage. | | Missed Opportunities (MOV) | Eligible child visits health facility but doesn't receive needed vaccines. System issue. | Identify & reduce. |> ⭐ NFHS-5 (2019-21) reported 76.4% full immunization coverage (12-23 months) in India, highlighting the gap from the >90% UIP target.

Challenges & Solutions - Bridging the Gaps

• Challenges (Barriers):
  • Operational: Vaccine logistics, cold chain, manpower shortage, AEFI monitoring.
  • Community: Low awareness, misinformation, vaccine hesitancy, migration, cultural beliefs.
  • Geographical: Hard-to-reach areas, difficult terrain.
• Solutions (Bridging Gaps):
  • Strengthen Service Delivery: Outreach, mobile teams, Reaching Every District (RED).
  • Boost Demand: IEC/BCC, community participation, address hesitancy.
  • Improve M&E: Supportive supervision, data analysis, eVIN, U-WIN.

⭐ Mission Indradhanush (MI) & Intensified Mission Indradhanush (IMI) target unvaccinated/partially vaccinated children (<2 yrs) & pregnant women in high-priority areas.

High‑Yield Points - ⚡ Biggest Takeaways

• WHO's 30x7 Cluster Sampling is standard for rapid coverage assessment.
• Lot Quality Assurance Sampling (LQAS) classifies areas by vaccination performance.
• Coverage Evaluation Surveys (CES) give periodic national/state estimates.
• Accurate denominator (target children) & numerator (vaccinated) are crucial.
• Vaccination cards are primary proof; recall/history is secondary.
• Target >80% routine coverage; >90-95% for measles to achieve herd immunity.
• Reducing Missed Opportunities for Vaccination (MOV) is vital.