## Immunisation in Severe Combined Immunodeficiency (SCID) ### Clinical Context SCID is a primary immunodeficiency with profound T-cell dysfunction (CD4 <500 cells/µL, often <100). This child is awaiting definitive treatment (stem cell transplant) and is at extreme risk of opportunistic infections. ### Key Point: Vaccination Strategy in SCID **Pre-transplant period:** - **Defer ALL vaccinations** (both live and inactivated) - The immune system cannot mount an adequate response - Inactivated vaccines may not generate protective antibodies - Live vaccines pose unacceptable risk of vaccine-strain disease **Post-transplant period (after immune reconstitution):** - Revaccinate with inactivated vaccines at 3–6 months post-transplant - Revaccinate with live vaccines at 12–24 months post-transplant (if CD4 >200 cells/µL and graft-versus-host disease resolved) ### High-Yield: IAP Approach to SCID Immunisation According to IAP guidelines, children with SCID should: 1. **Receive no vaccines** before stem cell transplant 2. **Avoid contact with recently vaccinated individuals** (especially rotavirus vaccine shedding from the sibling) 3. **Undergo revaccination** post-transplant after immune reconstitution ### Clinical Pearl The sibling's rotavirus vaccine is a concern because rotavirus vaccine virus can be shed in stool for up to 30 days post-vaccination. Immunocompromised household contacts should be counselled on strict hand hygiene, and the SCID child should be monitored for any signs of vaccine-strain rotavirus infection. ### Warning: Common Misconception ~~Giving inactivated vaccines now will provide some protection~~ — In SCID, the immune system cannot generate protective antibodies, and vaccinating now wastes time and resources. Revaccination post-transplant is the standard approach. ### Table: Vaccination Timeline in SCID | Phase | Timing | Action | Rationale | |---|---|---|---| | Pre-transplant | At diagnosis | Defer all vaccines | Immune system non-functional | | Peri-transplant | During conditioning | No vaccines | Immunosuppression | | Early post-transplant | 3–6 months post-engraftment | Inactivated vaccines | CD4 recovery; no GVHD | | Late post-transplant | 12–24 months post-engraftment | Live vaccines | CD4 >200; stable graft | ### Mnemonic: SCID Vaccination Rule **WAIT** = **W**ait for transplant, **A**void all vaccines pre-transplant, **I**nactivated vaccines post-transplant at 3–6 months, **T**hen live vaccines at 12–24 months.
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.