## Catch-Up Immunisation Strategy in a 9-Month-Old ### Key Principle: Accelerated Schedule with Minimum Intervals **Key Point:** In catch-up immunisation, all missed vaccines should be administered in a single visit or over consecutive visits, respecting **minimum intervals between doses** of the same antigen, but NOT restarting the entire schedule. ### Why Restart Is NOT Needed 1. **Doses already given count** — Once a child has received DPT 1 and DPT 2, those doses are immunologically valid. The schedule does not reset because of a missed booster. 2. **Minimum interval rule** — The interval between DPT 2 and DPT 3 should ideally be 6 months, but if missed, the child can receive DPT 3 after a **minimum of 4 weeks** from DPT 2 (per IAP guidelines). Since DPT 2 was given at ~10 weeks, DPT 3 can be given now at 9 months. 3. **No need to restart** — Restarting would mean giving DPT 1 again, which is wasteful and delays protection. The child already has priming from DPT 1 & 2. ### Catch-Up Immunisation Protocol at 9 Months **High-Yield:** Use the **"Accelerated Schedule"** approach: - Give all missed vaccines in a single visit - Respect minimum intervals between doses of the **same vaccine** - Different vaccines can be given simultaneously (different injection sites) - Do not wait 4 weeks between different antigens ### Minimum Intervals for Catch-Up (IAP Guidelines) | Vaccine | Minimum Interval from Previous Dose | |---------|-------------------------------------| | **DPT (booster 3)** | 4 weeks from DPT 2 | | **IPV (dose 3)** | 4 weeks from IPV 2 | | **Hepatitis B (dose 3)** | 4 weeks from Hep B 2 | | **Hib (dose 3)** | 4 weeks from Hib 2 | | **PCV (dose 3)** | 4 weeks from PCV 2 | | **OPV (dose 3)** | 4 weeks from OPV 2 | | **Rotavirus (dose 3)** | 4 weeks from Rotavirus 2 | **Clinical Pearl:** All these vaccines can be given **simultaneously** at the 9-month visit because they are different antigens. Only doses of the *same* vaccine must respect the 4-week minimum interval. ### Practical Approach ```mermaid flowchart TD A[9-month-old with missed vaccines]:::outcome A --> B{Any contraindications?}:::decision B -->|Yes| C[Defer contraindicated vaccines]:::action B -->|No| D[Give all missed vaccines simultaneously]:::action D --> E[DPT 3, IPV 3, Hib 3, PCV 3, OPV 3, Rotavirus 3, Hep B 3]:::action E --> F[Different injection sites]:::action F --> G[Schedule next visit at 12-15 months for boosters]:::action ``` **Mnemonic:** **CATCH-UP = Concurrent Administration, Timely Completion, Hurry Up Protection** - **C**oncurrent: Give multiple vaccines at once - **A**ccelerateIntervals: Use minimum 4-week intervals for same antigen - **T**iming: No need to restart - **C**omplete: All missed doses in one or two visits - **U**p: Catch up quickly to age-appropriate schedule - **P**rotection: Maximize immunity without delay [cite:IAP Immunisation Schedule 2023, Park 26e Ch 3]
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.