No New HIV Infections With Preexposure Prophylaxis

Tara Haelle

September 07, 2015

No individuals taking preexposure prophylaxis (PrEP) were diagnosed with HIV during 388 person-years of follow-up in a study published online September 1 in Clinical Infectious Diseases.

"This was despite high rates of STIs [sexually transmitted infections] — rectal STIs in particular — and self-reported decreases in condom use in 41% of a subset of PrEP users," write Jonathan E. Volk, MD, from Kaiser Permanente San Francisco Medical Center's Department of Adult and Family Medicine, California, and colleagues. The authors noted a dramatic increase in PrEP use, particularly starting in September 2013.

"Based on data from the placebo arm of a recent PrEP trial with a similarly high rate of rectal STIs, we would have expected an HIV incidence as high as 8.9 per 100 person-years in our study population in the absence of effective PrEP use," the authors write. "Our data suggest that fears about risk compensation resulting in increased HIV acquisition among PrEP users may be unfounded."

The researchers analyzed data from 801 individuals with at least one intake visit in the Kaiser Permanente San Francisco system who had been referred for PrEP evaluation between July 2012 — when the US Food and Drug Administration approved daily oral emtricitabine/tenofovir disoproxil fumarate (Truvada, Gilead) as PrEP — and February 2015.

Of these, 82% (657 individuals; average age, 37 years) began taking PrEP, continuing for an average of 7.2 months. Nearly all were men having sex with men; the exceptions were 3 heterosexual women and 1 transgender man who had sex with men.

Compared with the 18% who did not initiate PrEP, those who started it were no more likely to have an HIV-infected sex partner (30% PrEP vs 25% non-PrEP; P = .18). However, 84% of PrEP users reported multiple sex partners compared with 69% of those not taking PrEP (P < .001).

More than a third (35%) of those who did not start taking PrEP said they didn't because they had a low risk for HIV. Among other leading reasons for not taking it were concern about the cost (15%), lack of desire to complete the required follow-up (10%), and preference for postexposure prophylaxis (6.3%). Only a small percentage were concerned about adverse effects (2.8%) or increasing their sexual risk behavior (1.4%).

Just over a quarter (28.4%) of those who started PrEP were diagnosed with an STI during follow-up, and 11.9% had multiple STIs. By 12 months after starting PrEP, 50% of the users had any STI (95% confidence interval [CI], 43% - 56%), including 28% with gonorrhea (95% CI, 23% - 34%) and 5.5% with syphilis (95% CI, 3.3% - 9.1%). A third (33%) had a rectal STI (95% CI, 27% - 39%), and a third (33%) had chlamydia (95% CI, 27% - 39%). None were diagnosed with HIV during the entire follow-up (upper limit of one-sided 97.5% CI, 1.0%).

Among 143 persons surveyed about behavior changes after 6 months of taking PrEP, 74% said their number of sexual partners had not changed, 15% said it had decreased, and 11% said it had increased. Just over half (56%) did not change their condom use, 41% used condoms less often, and 3% used them more.

In an accompanying commentary, Kimberly A. Koester, MA, and Robert M. Grant, MD, MPH, from the University of California, San Francisco, commend the study authors "for creating a clinical environment conducive for gay and other men who have sex with men to feel comfortable enough to use their specialized PrEP program."

They also note the difficulty of interpreting the STI data.

"The increased [frequency] of STI testing offered during PrEP services affords more timely diagnosis and treatment of STIs, and high rates of diagnosis may reflect greater diagnostic yield rather than changes in sexual behavior," Koester and Grant write. "What appears to be high rates of STI diagnosis may reflect appropriate use of PrEP by people who have the most to benefit and people staying closer to their medical home for sexual health services," they write.

Yet they also state that the time has come "for a vigorous conversation about sexually transmitted infections, too long eclipsed by fear of HIV infection."

"Ideally," they write, "the public health response to the possibility of rising incidence of STIs in the context of decreased or no new HIV infections would be framed in relative terms and therefore considered to be a good problem to have."

The research was funded by Kaiser Permanente Northern California. One author has received research grants from Merck. The remaining authors have disclosed no relevant financial relationships.

Clin Infect Dis. Published online September 1, 2015. Abstract Editorial

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