Stark disparities seen all along the US PrEP continuum


Among a large US sample, women, Black, Latinx, younger and poorer people were less likely to receive PrEP prescriptions and start taking it, but were more likely to stop when compared to White, older men from higher socioeconomic backgrounds.

With almost 14,000 participants, this is one of the largest studies of the PrEP continuum to date. It was conducted by Dr J. Carlo Hojilla from the University of California, San Francisco and colleagues and reported in JAMA Network Open.


The Ending the HIV Epidemic initiative aims to reduce HIV incidence in the US by 90% by 2030. To achieve this ambitious target, more people need access to highly effective prevention in the form of pre-exposure prophylaxis (PrEP). This is crucially important for groups who have disproportionate numbers of new HIV infections: Black and Latinx communities, men who have sex with men, and substance users. Gaining a better understanding of patterns along the PrEP care continuum is crucial to attend to disparities in PrEP prescribing, starting and stopping.

The study

Kaiser Permanente Northern California is a large health care system and insurance provider providing care to 36% of the insured Californian population. Data for the study were taken from Kaiser Permanente’s electronic health records for adult members linked to PrEP care between 2012 (when PrEP was approved for use in the US) and 2019. Additional eligibility criteria included being on a health plan for at least six months during the study period and active insurance when starting PrEP. Individuals were followed either until the end of the study, an HIV diagnosis, loss of insurance for three months or more, or death.



Studies aim to give information that will be applicable to a large group of people (e.g. adults with diagnosed HIV in the UK). Because it is impractical to conduct a study with such a large group, only a sub-group (a sample) takes part in a study. This isn’t a problem as long as the characteristics of the sample are similar to those of the wider group (e.g. in terms of age, gender, CD4 count and years since diagnosis).

linkage to care

Refers to an individual’s entry into specialist HIV care after being diagnosed with HIV. 

continuum of care

A model that outlines the steps of medical care that people living with HIV go through from initial diagnosis to achieving viral suppression, and shows the proportion of individuals living with HIV who are engaged at each stage. 

person years

In a study “100 person years of follow-up” could mean that information was collected on 100 people for one year, or on 50 people for two years each, or on ten people over ten years. In practice, each person’s duration of follow-up is likely to be different.

The sample consisted of 13,906 people who were linked to PrEP care, 95% of whom were men, 49% were White, 22% were Latinx and 7% were Black. The median age was 33, with 40% aged between 25 to 35. There were approximately equal numbers in five socioeconomic groups, ranked from highest to lowest according to neighbourhood deprivation (20% in each group). A quarter of the group were classified as having an alcohol use disorder and 8% a substance use disorder at the time of PrEP linkage. Around 16% of the sample had been diagnosed with a bacterial sexually transmitted infection in the year prior or within a month of PrEP linkage.

PrEP prescriptions

This was defined as an order for emtricitabine and tenofovir disoproxil fumarate (or later, tenofovir alafenamide) with an indication for PrEP. Of those linked to PrEP care, 88% were prescribed PrEP by the end of the study. Older people were more likely to be prescribed PrEP than those aged 18 to 25. For instance, those over 45 were 21% more likely to be prescribed PrEP.

Women were almost half as likely (44%) to be prescribed PrEP as men. Black and Latinx people were 26% and 12% less likely to be prescribed PrEP than White people, respectively. Those in the lowest socioeconomic group were 28% less likely to receive a PrEP prescription than those in the highest socioeconomic group. People with a substance use disorder were 12% less likely to be prescribed PrEP.

Starting PrEP

This was defined as a pharmacy fill of the prescription. Of those prescribed PrEP, 98% started taking it. In keeping with patterns seen for PrEP prescriptions, people aged 45 and over were slightly more likely to start PrEP (9%), while women were 29% less likely to start than men. Similarly, Black and Latinx people were 13% and 10% less likely than White people to start taking PrEP. The socioeconomic pattern was also stable, as the lowest group was 7% less likely than the highest group to start PrEP. People with a substance use disorder were 12% less likely start PrEP.

Stopping PrEP and re-starting

Stopping PrEP for more than four months was defined as discontinuation. Over half of those who started PrEP discontinued it at least once during the study period (52%). The highest rates of stopping PrEP were within the first two years of starting. At two years, the cumulative proportion of those stopping was 38%. However, of those who stopped using PrEP at least once, 60% started using it again (an additional pharmacy refill) before the end of the study period.

People aged 45 and over were 54% less likely to stop taking PrEP. Women were twice as likely to stop taking PrEP compared to men. Black and Latinx people were also 36% and 33% more likely to stop taking PrEP than White people. However, interestingly, Black and Latinx people were also more likely to re-start PrEP after stopping (12% and 32%, respectively). The lowest socioeconomic group was 40% more likely to stop taking PrEP than the highest. People with a substance use disorder were 23% more likely to stop PrEP.

HIV diagnoses

In total, 136 people were diagnosed with HIV during the study period. A third of them were diagnosed when checking for PrEP eligibility during the linkage phase. Excluding those diagnoses, the HIV incidence rate was 0.35% overall, with a 0.87% incidence rate among those not prescribed PrEP, 1% among those who were prescribed it but did not start and 1.28% among those who stopped and did not re-start. There were no new infections on those who remained on PrEP over 9,139 person-years of follow-up.


“Encouragingly, we found that rates of PrEP prescription and initiation were high. However, priority populations for PrEP delivery, including members of racial and ethnic minority groups, young adults, women, individuals with lower socioeconomic status, and individuals with substance use disorders, were less likely to receive a PrEP prescription and initiate PrEP and more likely to discontinue PrEP despite comparable health care access,” the authors conclude.

“These findings suggest that health care access alone is not sufficient to optimize PrEP delivery and achieve national HIV prevention goals, including population impact and equity. Comprehensive strategies tailored toward high-priority populations are needed to mitigate attrition along the PrEP continuum of care.”


Hojilla J. Carlo, et al. Characterization of HIV Preexposure Prophylaxis Use Behaviors and HIV Incidence Among US Adults in an Integrated Health Care System. JAMA Network Open, published online 26August 2021 (open access).