Biostatistics & Study Design USMLE Step 1 Practice Question
A randomized controlled trial enrolls 500 healthy adults (mean age 35) during winter. Symptomatic, PCR-confirmed influenza develops in 10% of placebo recipients and 5% of vaccine recipients. Vital signs and chest X-ray remain normal in both groups. No participants report prior influenza vaccination. Approximately how many adults must be vaccinated to prevent one case of influenza during the season?
Answer choices
- A50
- B10
- C100
- D20Correct answer
- E5
- F2
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