Prevention & Control Strategies
Prevention occurs at three levels. Competition questions love asking: “At which level does this intervention act?” High scorers can instantly classify any measure — practice this!
Key Points
- Primary: Prevent disease before it occurs (vaccination, health education)
- Secondary: Early detection & treatment (screening, contact tracing)
- Tertiary: Reduce disability from established disease (rehab, case management)
- Herd immunity threshold ≈ 1 − (1/R₀)
- Isolation vs Quarantine: Isolation = sick person; Quarantine = exposed but well
- Ring vaccination: vaccinate contacts + contacts of contacts (used for Ebola)
- Chemoprophylaxis: antibiotics or antivirals for exposed individuals
Formulas & Concepts
Vaccine Efficacy:VE = (AR_unvaccinated − AR_vaccinated) / AR_unvaccinated × 100
Herd Immunity Threshold:HIT = 1 − (1/R₀)