There are now more options than ever before to reduce the risk of acquiring or transmitting HIV. Using medicines to treat HIV, using medicines to prevent HIV, using condoms, having only low-risk sex, only having partners with the same HIV status, and not having sex can all effectively reduce risk. Some options are more effective than others. Combining prevention strategies may be even more effective. But in order for any option to work, it must be used correctly and consistently. The following tables provide the best estimates of effectiveness for various strategies to prevent HIV acquisition or transmission. Each estimate was identified from the published scientific literature and represents the effectiveness of each strategy when used optimally. Available measures of optimal use vary by strategy. The principles for prioritizing measures and findings that were most relevant can be found here. A description of each prevention strategy, corresponding effectiveness estimate, and a summary of the evidence is provided below.
† Data are not available from these studies to calculate a combined confidence interval for the effectiveness estimate of 100%; however, confidence intervals for transmission rate estimates from each study are presented below. A recent review of many studies, including these, reported a combined HIV transmission risk estimate, across populations, while the HIV-positive person was virally suppressed of 0.00 (95% CI: 0.00 – 0.07) per 100 couple-years (Vernazza, 2019). Evidence Supporting Effectiveness Estimates:
References:
† The guidelines for PrEP use in the U.S. recommends daily oral PrEP (https://www.cdc.gov/hiv/pdf/risk/prep/cdc-hiv-prep-guidelines-2021.pdf [PDF – 2 MB]) and daily dosing is the only Food and Drug Administration (FDA)-approved schedule for taking PrEP to prevent HIV. Therefore, this summary evidence table refers to the science behind optimal or consistent use of daily PrEP and does not currently include on-demand PrEP. Although not included above, evidence also demonstrates that on-demand PrEP provides effective protection during sex for MSM as described below in the IPERGAY Trial and IPERGAY OLE. a Optimal use of oral daily PrEP is defined as taking PrEP daily. In studies, optimal or daily PrEP use has been determined by levels of TFV-DP detected in dried blood spots equivalent to 7 pills/week. Consistent use is defined as taking PrEP at least 4 pills/week, and has been measured in studies by levels of TFV-DP detected in dried blood spots or other objective adherence measures, consistent with at least 4 pills/week. b Recent use of oral PrEP is determined by detecting any amount of TFV in plasma. Evidence Supporting Effectiveness Estimatesc:
c The effectiveness estimate for PrEP is estimating the percentage reduction in HIV risk due to PrEP. It is not estimating the risk of HIV acquisition among those on PrEP, but is estimating the relative reduction in that risk due to PrEP. An effectiveness estimate of “about 99%” results in an extremely small estimated risk of HIV acquisition for those taking oral PrEP daily or consistently. References:
Evidence Supporting Effectiveness Estimates:
Strengths and Limitations of Effectiveness Estimates:
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