Los Angeles has one of the country's most serious intersecting crises of opioid addiction and HIV risk, and two proven tools to fight both remain stubbornly underused among people who inject drugs. A new federally funded study is testing whether getting peers to spread the word through their own social networks can change that.

The $771,043 grant from the Department of Health and Human Services will fund a clinical trial enrolling 372 people who inject drugs across Los Angeles. Half will receive a peer-led intervention called LINKED, which uses social network connections to encourage participants and their contacts to start pre-exposure prophylaxis (PrEP), the once-daily pill that prevents HIV infection, and medication for opioid use disorder (MOUD), such as buprenorphine or methadone. The other half will receive standard HIV and overdose risk education.

Researchers will track whether participants actually start and stick with those treatments at six and twelve months. Everyone in the study, regardless of which group they're in, will receive overdose prevention education and access to naloxone.

Los Angeles is designated a federal priority jurisdiction under the Ending the HIV Epidemic initiative, reflecting persistent transmission rates tied in part to injection drug use. Despite the availability of effective medications, uptake of both PrEP and opioid treatment among people who inject drugs remains low, a problem researchers attribute partly to stigma, distrust of healthcare systems, and lack of trusted messengers.

The LINKED approach bets that people are more likely to start treatment when someone in their own social circle encourages it. Participants are recruited through peer chain referral, meaning existing enrollees refer friends and contacts, building outward through real social networks rather than relying on clinic referrals alone. The study is being conducted in partnership with a peer-led organization in Los Angeles that already serves this population.

If the trial succeeds, researchers say the model could be replicated in other cities facing similar HIV and overdose burdens. Similar peer-focused strategies are being tested elsewhere, including New York hospitals pairing HIV prevention drugs with addiction treatment.

The trial runs through follow-up assessments at the one-year mark, with results expected to inform whether and how the approach gets scaled up in other high-priority jurisdictions.