Effectiveness of on-demand HIV pre-exposure prophylaxis versus daily prophylaxis

According to the results of a study published in HIV lancet.

Between May 2017 and May 2019, researchers conducted a prospective cohort study (ClinicalTrials.gov, NCT03113123) at 26 sites in France among HIV-negative adults at increased risk of HIV infection who were starting or continuing PrEP treatment. Researchers assessed the efficacy, compliance, and safety associated with on-demand PrEP use compared to daily use. Daily PrEP included a fixed-dose combination of tenofovir disoproxil and emtricitabine (245/200 mg). On-demand PrEP followed a 2-1-1 dosing regimen in which a loading dose is used 2 to 24 hours before sexual activity followed by a third and fourth dose 24 and 48 hours later, respectively. Tenofovir diphosphate and emtricitabine triphosphate concentrations were measured via dried blood spots, and patients reported adherence to PrEP. The primary endpoint was the incidence of HIV infection.

Of the 3056 patients included in the analysis, 1540 were in the daily PrEP group and 1509 were in the on-demand PrEP group. Of all patients, the median age was 36 (IQR, 29-43) years, 1344 (44.0%) were PrEP naïve, 1712 (56.0%) were already PrEP and 3016 (98.7% ) were men who have sex with men (MSM)

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Although 671 (43.6%) patients in the daily PrEP group switched to on-demand PrEP and 586 (38.8%) in the on-demand group switched to daily PrEP, the proportion of patients in both groups remained stable throughout the study period. The incidence of HIV infection was similar between patients in the two groups (incidence rate ratio [IRR], 1.00; 95% CI, 0.13-7.49; P =.99), with breakthrough infections noted in 3 patients in the daily PrEP group and 3 in the on-demand group. Of the total 6 patients diagnosed with HIV infection, all were MSM.

The researchers noted that the incidence of serious adverse events (AEs) was similar in the two groups of patients (IRR, 1.17; 95% CI, 0.89-1.53). Although the incidence of treatment-related AEs was low overall (IRR, 0.80; 95% CI, 0.89-1.53), a significantly increased rate was noted in patients in the groups On-demand vs daily PrEP (IR, 7.42 vs 5.93 per 100 person-years). Of note, 2 patients in each group discontinued PrEP due to gastrointestinal AEs.

Limitations of the study included the lack of randomized group assignment, the lack of a control group, and the number of patients lost to follow-up. These results may also have limited generalizability as the majority of patients were MSM residing in France.

According to the researchers, “further studies are needed to assess whether on-demand PrEP could be used in other populations at high risk of HIV infection, or with other combinations of antiretroviral drugs…”

Disclosure: Some authors have disclosed affiliations with biotechnology, pharmaceutical and/or device companies. Please see the original reference for a full list of disclosures.


Molina JM, Ghosn J, Assoumou L, et al. Daily and on-demand HIV pre-exposure prophylaxis with emtricitabine and tenofovir disoproxil (ANRS PREVENIR): a prospective observational cohort study. HIV lancet. Published online June 27, 2022. doi: 10.1016/S2352-3018(22)00133-3

Sara H. Byrd