A 9-month-old child presents to the immunisation clinic. The mother reports that the child received BCG at birth and DPT-1 at 6 weeks, but missed DPT-2 at 10 weeks and has not received any other vaccines. The child is clinically well with no contraindications. What is the most appropriate next step in management?

Explanation

## Management of Delayed Immunisation — Catch-Up Schedule ### Clinical Scenario A 9-month-old with incomplete primary series (only DPT-1 at 6 weeks; missed DPT-2 at 10 weeks). The child is otherwise healthy and has no contraindications. ### Key Point: **In the NIS, if a scheduled dose is missed, the next dose should be given as soon as possible without restarting the series. There is no need to restart if the interval between doses is longer than recommended — the child's immune response to previous doses is retained.** ### National Immunisation Schedule — DPT Primary Series | Dose | Scheduled Age | Minimum Interval from Previous Dose | | --- | --- | --- | | DPT-1 | 6 weeks | — | | DPT-2 | 10 weeks | 4 weeks | | DPT-3 | 14 weeks | 4 weeks | | Booster-1 | 18 months | ≥6 months after DPT-3 | | Booster-2 | 5 years | ≥1 year after Booster-1 | ### Catch-Up Principle 1. **Do NOT restart the series** — the child has already received DPT-1 (6 weeks ago); immunity has been primed 2. **Give the next dose (DPT-2) immediately** — at 9 months, there is adequate interval from DPT-1 (3 months) 3. **Continue with DPT-3** — 4 weeks after DPT-2 4. **Booster-1** — at 18 months (≥6 months after DPT-3) ### High-Yield: **The "catch-up" rule: If a dose is missed, give it as soon as possible and continue the schedule from that point. Restarting is NOT required unless >10 years have elapsed since the last dose (which is not the case here).** ### Clinical Pearl: Missed doses do not erase prior immunity. The immune system "remembers" the first dose (DPT-1); the second and third doses boost and consolidate that response. Restarting wastes time and resources. ### Mnemonic: **"CATCH-UP, Don't START-OVER"** — If a dose is late but the child has received at least one prior dose, catch up with the next scheduled dose; do not restart the entire series. ### Recommended Action Plan 1. Administer DPT-2 at this visit (9 months) 2. Schedule DPT-3 for 4 weeks later (approximately 10 months) 3. Schedule Booster-1 at 18 months 4. Administer other missed vaccines (OPV-2, OPV-3, hepatitis B-2, hepatitis B-3, rotavirus-2, rotavirus-3, measles) according to catch-up schedule [cite:NIS Guidelines 2023, Park 26e Ch 6]