Truvada for PrEP provides 92%-99% reduction in HIV risk for HIV-negative individuals who take the pills every day as directed. If a daily dose is missed, the level of HIV protection may decrease. It only works if you take it. People who use PrEP correctly and consistently have higher levels of protection against HIV.
According to data analysis from the iPrEx study that found PrEP to be effective:

  • For people who take 7 PrEP pills per week, their estimated level of protection is 99%.
  • For people who take 4 PrEP pills per week, their estimated level of protection is 96%.
  • For people who take 2 PrEP pills per week, their estimated level of protection is 76%.

There are not enough data available to provide specific timing guidance on non-daily use, so the FDA recommends PrEP be used daily to achieve the highest level of protection.
A few things to note:

  • When starting PrEP, it takes at least seven days to reach high levels of protection against HIV.
  • When stopping PrEP, individuals should continue using PrEP for four weeks after the last significant exposure.
  • PrEP does not protect against other sexually transmitted infections (STI) or pregnancy. It is not a cure for HIV.
"If you don’t take PrEP consistently it can’t protect you from HIV, but if you do take it regularly it can offer strong protection."





"several studies suggest that PrEP can be effective for both men and women at risk for HIV infection"