Vaccines and Immunoprophylaxis · USMLE Step 1

A patient receives a vaccine containing purified polysaccharide antigens that stimulate B cells without T-cell help. Which vaccine fits this description?

  1. PCV13
  2. PPV23
  3. Hib conjugate
  4. Tdap
Show answer and explanation

Correct answer: PPV23

PPV23 contains unconjugated polysaccharides, producing a T-cell–independent response. It is less immunogenic in young children.

Difficulty: Medium Question 14 of 20

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