A 12-year-old boy in a dengue-endemic city is being considered for CYD-TDV (Dengvaxia) vaccination. Before administering the vaccine, which finding must be established, and why?
- A Platelet count above 150,000/mm3, because thrombocytopenia predicts adverse reactions
- B Negative NS1 antigen, because the vaccine interferes with antigen detection
- C Evidence of prior dengue infection, because seronegative recipients have an increased risk of severe dengue after vaccination ✓
- D Family history of allergy, because the vaccine is contraindicated in first degree relatives of allergic individuals
Correct answer: C. Evidence of prior dengue infection, because seronegative recipients have an increased risk of severe dengue after vaccination
Explanation
WHO recommends CYD-TDV only for persons with confirmed past dengue infection, demonstrated by serological screening, because in seronegative recipients the vaccine behaves like an asymptomatic primary infection, and a subsequent natural infection then acts as a secondary infection with higher risk of severe dengue. Platelet status, NS1 result and family history have no bearing on eligibility, which removes the remaining distractors.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.