Two HIV prevention methods are 100% and 99% effective, according to "best estimates" based upon peer-reviewed studies. They are outlined in the CDC table, Effectiveness of Prevention Strategies to Reduce the Risk of Acquiring or Transmitting HIV. Release date: July 18, 2019.
As for the methods with head-turning efficacy:
- For HIV-positive individuals who take antiretroviral therapy and achieve and maintain viral suppression: 100%
- For HIV-negative individuals who take PrEP daily: 99%
The CDC table presents efficacy estimates along with dozens of peer studies. In addition to the two prevention methods summarized above, the table presents efficacy data on male condom use and circumcision of adult males.