Men, older people, city residents and those with commercial insurance remain on pre-exposure prophylaxis (PrEP) longer than women, young people, rural residents and those covered by Medicaid, according to research presented at the Conference on Retroviruses and Opportunistic Infections (CROI) this month in Seattle.

A related study found that among young Black men who have sex with men in Atlanta—a population at high risk for HIV—stopping and restarting PrEP was common.

Truvada (tenofovir disiproxil fumarate/emtricitabine) taken once daily or “on demand” dramatically reduces the risk of acquiring HIV. Many studies have looked at factors that influence PrEP adherence, meaning consistently taking the prescribed dose on schedule. Now, researchers are turning to PrEP persistence, or how long people continue to use it.

Ya-Lin Huang, PhD, of the Centers for Disease Control and Prevention, and colleagues looked at factors that affect PrEP persistence among people covered by commercial health insurance or Medicaid.

They used data from the IBM MarketScan commercial insurance database, which includes claims data for 40 to 50 million people with employer-sponsored health insurance, and the IBM MarketScan Medicaid database, which includes data for 8 to 13 million enrollees in up to 10 unidentified states each year.

The analysis included people ages 18 to 64 who started using Truvada for PrEP between 2012—the year it was approved for HIV prevention—and 2016. The study was limited to those continuously enrolled in a health plan for six months before and six months after their first PrEP prescription.

PrEP persistence was defined as the time from the first filled prescription until there was a gap of more than 30 days since the last prescription ran out. The analysis did not track those who restarted PrEP after more than a 30-day lapse.

The commercial insurance group included 7,250 people, almost all of whom were men (98 percent) and urban residents (97 percent). About 60 percent were ages 25 to 44. All geographic areas were represented. The Medicaid group was smaller, with 349 people; 78 percent were men, 43 percent were white, 23 percent were Black and 34 percent were “other” (including Latino); two thirds fell into the 25 to 44 age group. The commercial database didn’t include data about race/ethnicity, and neither data set included information about sexual orientation or gender identity.

People with commercial insurance stayed on PrEP longer than those covered by Medicaid, Huang reported. The median duration of PrEP use was 14.5 months for the commercial group versus 7.6 months for the Medicaid group. A year after starting PrEP, more than half (56 percent) of those covered by commercial insurance were still using it, compared with about a third (34 percent) of Medicaid recipients. PrEP persistence continued to decline, and fewer people were still on it at 18 months.

Men were more likely to persist on PrEP than women: 14.5 months versus 6.9 months, respectively, in the commercial group and 8.4 versus 5.8 months in the Medicaid group. After a year, 56 percent of men and 40 percent of women with commercial insurance and 37 percent versus 23 percent on Medicaid were still taking PrEP. Of note, some HIV-negative women with HIV-positive partners use PrEP while trying to conceive, which may limit the amount of time they feel they need to use it.

PrEP persistence was found to increase with age. The median duration was 20.5 months for those ages 45 to 54 versus 8.6 months for those ages 18 to 24 in the commercial group and 10.0 and 4.0 months, respectively, in the Medicaid group. After a year, 64 percent of commercially insured people and 41 percent of Medicaid recipients were still on PrEP in the older group, compared with 37 percent and 20 percent, respectively, in the youngest group.

In the Medicaid cohort, white people stayed on PrEP for a median of 8.5 months, and “others” did so for 8.1 months, falling to 4.1 months for Black people. Here, 38 percent of white people and 23 percent of Black people remained on PrEP at one year.

Huang cautioned that the reasons people discontinued PrEP in this study are not known. Ideally, PrEP persistence should be measured during periods of risk, she said; if a person is entering a period of low or no risk, stopping PrEP isn’t a concern. Another limitation is that people without either commercial insurance or Medicaid were not included—a population that may have more difficulty maintaining a steady PrEP supply.

Commenting on the study, HIV prevention expert Sharon Hillier, PhD, of the University of Pittsburgh, said the findings show a mismatch between the people who could benefit most from PrEP and those who stay on it. This underscores the need for better strategies to help people make PrEP a regular part of their lives, she said.

Persistence Among Young Black Gay Men

In a related study, David Serota, MD, of Emory University in Atlanta, and colleagues looked at PrEP persistence in one of the groups at highest risk for HIV: young Black gay and bisexual men in the South. In their cohort, HIV incidence remains around 6 percent per year among those with access to PrEP services, Serota said.

The EleMENt study looked at substance use and HIV risk behavior among 298 young (ages 18 to 29) Black men who have sex with men in Atlanta. All participants were offered PrEP at each study visit, which took place every four months for two years. Lab tests, transportation and free or low-cost Truvada were provided by the study. Here, PrEP discontinuation was defined as a lapse of more than two weeks.

Of the 125 young men who started PrEP, 46 (37 percent) were classified as “fully persistent.” Sixty-three percent discontinued PrEP at least once—after a median of 7.3 months—but over two thirds of these subsequently restarted. About one in five stopped PrEP two or more times.

“Most who stopped restarted PrEP at some point but not without significant gaps in PrEP coverage,” the researchers said.

Men younger than 22 were about four times more likely to stop PrEP. Marijuana use (but not other drugs or alcohol) and recent sexually transmitted infections were also linked to PrEP discontinuation as was having fewer than three anal sex partners in the past six months—perhaps reflecting men who no longer saw themselves as being at high risk for HIV.

Serota’s team suggested that regimens that do not require adherence to daily pills—such as “on demand” or “event driven” PrEP taken before and after sex—may be a potential option for young gay and bi men who discontinue PrEP because of low levels of risk behavior.

Click here to read Huang’s study abstract.

Click here to read Serota’s study abstract.

Click here to learn more about PrEP.