The BCG vaccine is a live attenuated vaccine derived from Mycobacterium bovis. In a child with DiGeorge syndrome (thymic aplasia), administering BCG carries a specific risk. What is this risk?
- A Anaphylaxis due to IgE-mediated hypersensitivity to mycobacterial antigens
- B Disseminated BCG infection (BCGosis) due to absent T-cell-mediated immunity ✓
- C BCG-induced granuloma formation causing local abscess only
- D No additional risk compared to immunocompetent children
Explanation
DiGeorge syndrome involves absent or severely reduced T cells due to thymic aplasia. Live vaccines (BCG, OPV, MMR, varicella) are contraindicated in T-cell immunodeficiencies because the attenuated vaccine organism cannot be cleared without T-cell immunity, leading to disseminated infection — 'BCGosis' with regional lymphadenopathy, osteitis, and systemic dissemination. This is also a risk in HIV-positive infants, SCID, and children on immunosuppressants. Killed/subunit/toxoid vaccines are safe in T-cell immunodeficiency but may not elicit adequate responses. All live vaccines are contraindicated in primary T-cell immunodeficiencies.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.