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Conjugate vaccine T-dependent response — MRCPCH TAS MCQ

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ModerateImmunologyConjugate vaccine T-dependent responseMRCPCH TAS

An infant receives a Hib conjugate vaccine. The polysaccharide antigen is linked to a protein carrier to improve protection in early life. What immune principle explains this?

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Correct answer: A — Recruitment of T-cell help and immunological memory

Conjugate vaccines convert a poorly immunogenic polysaccharide response into a T-dependent response with class switching and memory. Pure polysaccharide vaccines are less effective in young infants because T-independent responses are immature. The pearl is that conjugation is central to Hib and pneumococcal vaccine effectiveness in infancy.

Reference: UKHSA Green Book; Nelson Textbook of Pediatrics; RCPCH Theory examination syllabi