Quick Answer

PrEP (pre-exposure prophylaxis) is taken daily or on-demand to prevent HIV acquisition, with >99% effectiveness when taken as prescribed. PEP (post-exposure prophylaxis) is a 28-day course of antiretrovirals started within 72 hours of a potential HIV exposure, also extremely effective when initiated promptly.

  • PrEP: daily Truvada or Descovy (or injectable cabotegravir every 2 months).
  • PrEP effectiveness: >99% for daily oral; >98% for On-Demand (2-1-1 schedule for men who have sex with men).
  • PEP: 28-day course, started within 72 hours, ideally within 24. Effectiveness >90% with full adherence.
  • PEP is for EMERGENCIES — condom breakage with known-positive partner, sexual assault, needle sharing.

Context Most Pages Skip

PrEP and PEP reversed the HIV prevention landscape. Before PrEP, the only prevention was condoms and partner selection. Now, people at risk can take a single pill that eliminates HIV from the equation entirely.

Getting on PrEP

Discuss with any provider. PrEP requires baseline HIV testing, kidney function monitoring, and quarterly follow-up. Many insurance plans and state programs cover it fully. Online services also prescribe.

⚕️ This page is educational and does not replace advice from a licensed clinician. If you may have been exposed to an STI, get tested — most infections are manageable, and many are fully curable.

Sources & Further Reading

Figures reflect CDC surveillance and WHO estimates; they are population statistics, not personal risk predictions.