Global HIV Programme - Pre-exposure prophylaxis (PrEP)

Pre-exposure prophylaxis, commonly known as “PrEP,” involves the administration of antiretroviral medication to HIV-negative individuals to significantly lower their likelihood of contracting HIV.

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According to recommendations from the WHO as of September 2015, people at high risk of HIV infection should consider tenofovir disoproxil fumarate (TDF)-based oral PrEP as a preventative measure within a comprehensive prevention strategy. This form of PrEP is very effective when taken as prescribed. In 2021, WHO added that the dapivirine ring could be another viable prevention option for women at elevated risk of HIV. In 2022, the introduction of long-acting injectable cabotegravir (CAB-LA) was recommended as an additional option for those facing substantial HIV risk. Moreover, ongoing research is exploring other PrEP products, such as multipurpose prevention products that combine antiretroviral drugs with contraceptives.

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Risks of HIV Drug Resistance in PrEP Users

Despite concerns about the possibility of drug resistance for those who acquire HIV while on tenofovir DF-emtricitabine, tenofovir alafenamide-emtricitabine, or injectable cabotegravir, large-scale HIV PrEP studies have shown low incidences of resistance development. For instance, in the iPrEx study, out of 48 participants who acquired HIV while on tenofovir DF-emtricitabine, only 2 exhibited resistance mutations, which were detectable only through deep sequencing methods. The Partners PrEP study revealed that 5 out of 63 (7.9%) individuals who seroconverted while taking active HIV PrEP developed resistance, with higher occurrences in the tenofovir DF-emtricitabine group compared to the tenofovir DF-only group. In the HPTN 083 trial involving cabotegravir, 4 out of 9 breakthrough infections displayed resistance to integrase strand transfer inhibitors while mutations (K65R, M184V, M184I) appeared in individuals with tenofovir DF-emtricitabine. These findings indicate that the occurrence of HIV PrEP-related resistance is minimal if HIV infection is ruled out before starting PrEP, and if regular HIV testing is conducted in ongoing PrEP users.

Assessing Suspected HIV Drug Resistance

If someone on HIV PrEP is diagnosed with HIV, an HIV RNA level test and an HIV genotype resistance assay should be immediately performed. In some cases, individuals may test below the reliable detection range for HIV genotyping due to partial suppression of viral replication by PrEP medications. In such situations, the role of HIV DNA genotyping (aka proviral genotype) remains unclear, though it can be conducted even with very low or undetectable HIV RNA levels. If HIV is acquired while on oral PrEP (tenofovir DF-emtricitabine or tenofovir alafenamide-emtricitabine) or following recent use of oral PrEP, the standard genotype should evaluate mutations in the reverse transcriptase and protease genes. However, if injectable cabotegravir was utilized and HIV is later contracted, an expanded genotype must also check for resistance-associated mutations in the integrase gene due to the drug's prolonged half-life, and this may necessitate a separate lab request.

Routine Monitoring to Prevent HIV Drug Resistance

Initial HIV testing is critical before starting PrEP to ensure that individuals with undiagnosed HIV do not receive an ineffective regimen, which could lead to rapid development of drug resistance. Continuous HIV testing is also crucial for PrEP users to minimize exposure duration to PrEP if they contract HIV. The CDC’s 2021 PrEP Clinical Practice Guidelines recommend dispensing no more than 90 days of medication at a time and re-testing HIV status every three months for oral PrEP users. For MSM using on-demand (2-1-1) PrEP with tenofovir DF-emtricitabine, a maximum of 30 pills should be provided before the next HIV test, allowing medication for seven exposure events. Those on injectable cabotegravir should undergo HIV testing at the initial injection and every two months subsequently, following the injection schedule. Testing for those on oral or injectable PrEP should include both an HIV-1/2 antigen-antibody assay and HIV-1 RNA testing. If symptoms of acute HIV develop, additional HIV testing, including an HIV RNA assay, should be done.

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What is PrEP and how effective is it?

PrEP (Pre-exposure Prophylaxis) is a preventive strategy in which HIV-negative individuals take antiretroviral medication to lower the risk of HIV infection. When taken consistently, PrEP has been shown to reduce the risk of HIV transmission by up to 99% in people who have a high risk of HIV.

Are there different forms of PrEP available?

Yes, PrEP is available in several forms, including daily oral pills, the dapivirine vaginal ring (specifically for women), and long-acting injectable versions like cabotegravir. Research is ongoing to develop additional options, such as multipurpose prevention technologies that integrate contraceptives.

What are the common side effects of PrEP?

Common side effects of oral PrEP medications like tenofovir DF-emtricitabine include nausea, headaches, and mild gastrointestinal issues. These side effects often diminish over time. Injectable cabotegravir may cause injection site reactions and sometimes mild flu-like symptoms.

Is PrEP suitable for everyone?

PrEP is recommended for individuals at high risk of HIV, such as those with HIV-positive partners, people who have multiple sexual partners, or those who engage in unprotected sex. Consulting a healthcare provider can help determine if PrEP is a suitable option based on individual risk factors.