The following article is a part of conference coverage from the IDWeek 2021, being held virtually from September 29 to October 3, 2021. The team at Infectious Disease Advisor will be reporting on the latest news and research conducted by leading experts in the field. Check back for more from the IDWeek 2021.

A pooled analysis from large, diverse, multi-national studies found that HIV pre-exposure prophylaxis (PrEP) with daily emtricitabine/tenofovir disoproxil fumarate (F/TDF) significantly decreases the risk for HIV infection in individuals who adhere to treatment. These findings were presented at IDWeek, held virtually from September 29 to October 3, 2021.

This study included pooled data from 19 PrEP trials comprising a total of 6613 participants. All participants were followed for a period of 48 to 96 weeks, and adherence to PrEP was determined via measurement of tenofovir-diphosphate (TFV-DP) concentrations in dried blood samples. The researchers used Poisson regression to calculate the rate of incident HIV infection.

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Among patients included in the study, 82% were men, 12% were women, 5% were transgender individuals, and the median age was 30 (interquartile range [IQR], 24-38) years.

After stratification by incident HIV infection, the researchers found that patients who developed incident HIV infection (n=69) had consistently decreased concentrations of TFV-DP. In addition, patients who developed incident HIV infection adhered to PrEP for a median of 0.82 years and had an overall incident rate of 1.16 (95% CI, 0.92-1.47) per 100 person-years.

The researchers noted a significant association between PreP adherence and incident HIV infection. Among patients who received less than 2 (21%), 2 to 3 (14%), 4 to 6 (36%), and 7 or more (29%) F/TDF tablets weekly, incident HIV infection rates were 5.20 (95% CI, 4.03-6.71), 0.38 (95% CI, 0.12-1.18), 0.28 (95% CI, 0.12-0.61), and 0.06 (95% CI, 0.01-0.39), respectively, per 100 person-years.

After stratification by patient gender, the greatest increase in the rate of incident HIV infection per 100 person-years occurred among those who identified as men (1.25; 95% CI, 0.98-1.60), followed by those who identified as women (0.71; 95% CI, 0.27-1.90), and then those who identified as transgender (0.63; 95% CI, 0.16-2.53).

In regard to individuals at increased risk for incident HIV infection, “these findings support ongoing efforts to increase PrEP [adherence],” the researchers concluded.

Disclosure: Some author(s) declared affiliations with industry. Please see the original reference for a full list of disclosures.


Liu A, Grant R, Landovitz RJ, et al. Adherence to F/TDF for PrEP in dried blood spots and HIV infection rates: a pooled analysis of global PrEP studies. Presented at: IDWeek; September 29 to October 3, 2021.Poster 866.

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