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?
- A)50
- B)10
- C)100
- D)20GABARITO
- E)5
Explicação
Number needed to vaccinate is calculated the same way as number needed to treat: 1 divided by the absolute risk reduction. The absolute risk reduction is 10% minus 5% = 5%, or 0.05. Thus, 1/0.05 = 20 people must be vaccinated to prevent one case. Ver explicação completa e trilha adaptativa →