A chemoprophylaxis regimen is administered to household contacts during a meningococcal outbreak. Baseline vital signs are stable; temperature 37.2°C, HR 88/min, BP 118/76 mmHg. Cerebrospinal fluid cultures from the index case confirm Neisseria meningitidis. The attack rate is 12% in untreated contacts and 3% in treated contacts who received rifampin prophylaxis. No adverse medication reactions are documented. Which of the following best represents the prevented fraction among the treated contacts?
- A)9%
- B)50%
- C)75%GABARITO
- D)25%
- E)400%
Explicação
Prevented fraction among the exposed equals the relative reduction in risk among treated individuals: (risk in unexposed minus risk in exposed) divided by risk in unexposed. Here, (0.12 - 0.03)/0.12 = 0.75, or 75%. This means prophylaxis prevented three quarte... Ver explicação completa e trilha adaptativa →