PrEP in a clinical setting: no infections reported in San Francisco cohort

Simon Collins, HIV i-Base

Experience of PrEP use outside a clinical trial in a high incidence population were presented from a retrospective analysis of people accessing care at the Kaiser Permanente Medical Centre in San Francisco, California.

This analysis described all patients at the centre who were evaluated for and started on PrEP from July 2012 (when PrEP was approved in the US) to February 2015. The results were reported by Jonathan Volk and colleagues and are available as an open access paper in the 1 September edition of Clinical Infectious Diseases. [1]

Use was low during the first year (less than 5 to 10 people starting PrEP each month), steadily increasing to approximately 40 people a month at the end of the second year and reaching 50 to 60 for the last six months. Approximately 80% of the 1045 referrals led to an evaluation with at least one clinic visit (n=908) and of these, 657 individuals started PrEP. This cohort was 99% gay men, with one heterosexual women and one transgender man.

During 388 person years of PrEP use, with a mean duration of use of 7.2 months, there were no new HIV diagnoses. This was despite 187 people being diagnosed with at least one STI and 78/178 being diagnosed with multiple STIs (range 2 to 10) indicating likely ongoing HIV exposure and risk.

After 12 months of PrEP use, half the people using PrEP were diagnosed with an STI (95% CI: 43% to 56%), including one-third with a rectal STI, one-third with chlamydia, 28% with gonorrhoea and 5.5% with syphilis.

Although there was no control group or historical data of previous STIs, based on the high rate of rectal STIs, the researchers estimated an expected incidence of HIV without PrEP of 8.9/100 patient years.

An accompanying editorial noted that an increase in STIs among gay men had been reported as predating PrEP and that against a background of zero HIV infections – the key goal – and a lack of control date, that the high rates of STIs might even be “considered a good problem to have”.


  1. Volk JE et al. No new infections with increasing use of HIV preexposure prophylaxis in a clinical practice setting. Clin Infect Dis (2015): 61(10):1601-1603. doi: 10.1093/cid/civ778. Free online. (1 September 2015).
  2. Koester KA and Grant RM. Keeping our eyes on the prize: no new HIV infections with increased use of HIV pre-exposure prophylaxis. Editorial commentary, Clin Infect Dis. 61:1604-1605. doi: 10.1093/cid/civ783. (01 September 2015).

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