Paper I
2023 March (Supplementary) (2010 Scheme) · 40 marks · 120 min

Question

Adjuvant.

Q92 marksShort Notes

Answer

Adjuvants are substances added to a vaccine that, while not themselves immunogenic, enhance and prolong the specific immune response to the co-administered antigen — allowing a smaller antigen dose, fewer doses, and/or a stronger, longer-lasting immune response than the antigen would elicit alone.

Mechanisms: depot effect (slow-release reservoir at the injection site, prolonging antigen exposure), enhanced antigen uptake/presentation by antigen-presenting cells, and direct immune stimulation via pattern-recognition receptors (e.g., Toll-like receptors), mimicking a natural “danger signal.”

Examples: aluminium salts (alum) — the most widely used adjuvant in human vaccines (DPT, hepatitis B); Freund’s adjuvant — experimental/research use only; oil-in-water emulsions (MF59, AS03) — used in some influenza vaccines; Toll-like receptor agonists (monophosphoryl lipid A, CpG oligonucleotides).

Clinical relevance: adjuvants are particularly important for killed/inactivated and subunit vaccines (inherently less immunogenic since they do not replicate in the host), allowing these safer vaccine types to still generate adequate protective immunity.

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