As PrEP knowledge increases in San Francisco, 12,500 people now thought to be on PrEP

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Knowledge about and use of HIV pre-exposure prophylaxis (PrEP) has greatly increased over the past few years in San Francisco, and surveillance estimates suggest that some 12,500 people are now on PrEP, most of them gay and bisexual men, according to a presentation at the HIV Research for Prevention conference (HIVR4P) last week in Chicago. 

PrEP use has increased dramatically over the past few years as clinical trials and demonstration projects continue to confirm its safety and efficacy. Studies of gay and bisexual men have shown that Truvada (tenofovir/emtricitabine) reduces the risk of HIV infection by more than 90% if used consistently, with no new infections seen among people who take it at least four times a week.

It has been difficult to estimate how many people have used Truvada for PrEP, as this information is not centrally collected. A recently reported survey of retail pharmacies by Gilead Sciences found that more than 79,000 people in the US have taken PrEP over the past four years, but this does not include people who received PrEP through various studies or through public or private programmes that do not report their numbers.



An umbrella term for people whose gender identity and/or gender expression differs from the sex they were assigned at birth.

cisgender (cis)

A person whose gender identity and expression matches the biological sex they were assigned when they were born. A cisgender person is not transgender.

community setting

In the language of healthcare, something that happens in a “community setting” or in “the community” occurs outside of a hospital.

demonstration project

A project that tests and measures the effect of a treatment or prevention approach in a ‘real world’ setting. Usually done after clinical trials have shown that the intervention is efficacious, but while there are outstanding questions about how it can be best implemented.


How well something works (in a research study). See also ‘effectiveness’.

San Francisco is known to be at the forefront of widespread PrEP adoption. The city's large and well-informed gay community has promoted its use, and supportive politicians and public health officials have provided resources for expanding PrEP access as part of the city's 'Getting to Zero' initiative.

Susan Scheer of the San Francisco Department of Public Health (DPH) presented findings from an analysis of knowledge about PrEP and trends and disparities in PrEP use among people at risk for HIV in the city.

The researchers collected data from people seen at City Clinic (a large DPH sexually transmitted disease clinic), DPH-funded primary care clinics and Kaiser Permanente San Francisco. In addition, they looked at community-based self-reported data from the National HIV Behavioural Surveillance (NHBS) system, City Clinic patient interviews, clients at community-based HIV testing sites and a survey by the Stop AIDS Project, now part of the San Francisco AIDS Foundation's Strut health and wellness centre for gay, bisexual and trans men.

While only 19% of City Clinic clients knew about PrEP in 2011 – the year after results from the pivotal iPrEx trial were published – this increased to more than 80% by 2014. Data from 2016 show that although around 90% of clients at City Clinic and Strut were knowledgeable about PrEP, this fell to 71% of those visiting community HIV testing sites.

Turning to self-reported use, in 2014 10% of NHBS respondents, 14% of City Clinic clients and 16% of Stop AIDS survey respondents said they had used PrEP. By 2016, 29% of City Clinic clients and 44% of Strut clients said they had used PrEP, but this fell to just 11% at community testing sites.

Several studies have found that gay men of colour and women are less likely to use PrEP compared to white gay men, and this was reflected in the data about PrEP knowledge and reported use.

Among City Clinic and Strut clients, PrEP awareness was high across all racial/ethnic groups: around 85% of African Americans, 87% of Latinos, 89% of Asians and 92% of white people. But at community testing sites the disparity was greater: 50% of black people versus 88% of white people, with Latinos and Asians falling in between.

Overall, people under age 18 and over 50 were less likely to know about PrEP. Only about a third of cisgender (non-transgender) women at City Clinic and the testing sites knew about PrEP, although awareness was high among transgender women and men (87% and 84%, respectively).

PrEP use followed a similar pattern. Black clients were somewhat less likely to report PrEP use than white clients: 25% vs 31% at City Clinic, 40% vs 48% at Strut and 6% vs 10% at community testing sites. Latinos were about as likely to use PrEP as white people. Again, people under 18 and over 50 were less likely to report PrEP use. Only about 3% of cisgender women did so, compared with roughly a third of cisgender men and trans women and men.

Although African Americans accounted for 17% of new HIV infections in San Francisco in 2015, the proportion of black PrEP users ranged from less than 5% to just over 10% at the various sites. PrEP use among Latinos and Asians roughly matched their share of new HIV infections, while use among white people exceeded their 42% share of new infections.

Kaiser and Strut were disproportionately more likely to see white PrEP users and less likely to see people of colour. DPH primary care clinics came closest to having their PrEP users match the racial/ethnic distribution of new infections in the city, and were the only sites to serve a substantial number of female PrEP users.

Dr Scheer explained that the DPH does not do name-based PrEP surveillance, PrEP prescriptions are not reportable by providers or pharmacies, and there are no standard indications or diagnostic codes for PrEP. Instead, health officials must rely on sentinel site surveillance, provider logs, and surveys of local gay men, clinic clients and people receiving HIV tests. As such, estimates of the total number of PrEP users are at best approximations.

“Measuring PrEP knowledge and use is difficult,” Dr Scheer said. “There is no formal surveillance system for PrEP like there is for HIV. A CDC study presented at the HIVR4P conference found that only 13% of health departments across the U.S. are even attempting to monitor PrEP use.”

Current estimates suggest that approximately 12,500 San Franciscans are now on PrEP.

“The 12,500 is an estimate – it does not come from adding up individual sites that have reported PrEP use to us,” Dr Scheer explained. “Pulling together existing data from community-based sources and clinics prescribing PrEP and comparing this to the estimates of PrEP-eligible persons – for example, 25% of men who have sex with men (MSM) reporting PrEP use in 2016 and an estimated 50,000 HIV-negative MSM in San Francisco – we estimate that about 12,000 to 13,000 people are now using PrEP.”

“Obtaining actual numbers from sites is difficult – people go on and off PrEP, so determining current users is hard, sites often can only guess at the numbers on PrEP, and some sites can't pull the information from their medical records and therefore don't even provide an estimate to us,” she added.  

A recent informal survey of large PrEP providers found that Strut had reached 1000 prescriptions and Kaiser had hit 1800 by June 2016, most of them to gay and bisexual men. In addition, over 500 people had started PrEP at City Clinic (not including clients who rolled over to regular prescriptions following enrolment in the PrEP Demo Project) and about 220 people were on PrEP at the primary care clinics.

The DPH aims to have 15,000 people on PrEP by 2017 and around 2500 new PrEP starts next year. But Dr Scheer emphasised that not all populations at high risk of HIV are being reached by current PrEP programmes, particularly young people, African Americans and women.

“PrEP knowledge and use in San Francisco has been rapidly rising,” Dr Scheer told Aidsmap. “It is important to monitor PrEP use so that gaps in knowledge and use can be identified and resources can be used to target those not currently being reached. We want to be a city where everyone who would benefit from PrEP knows about it and has equal and easy access to it.”


Scheer S et al. PrEP Knowledge and Use in San Francisco. HIV Research for Prevention Conference (HIVR4P 2016), Chicago, abstract OA24.03, 2016.