The first time Devin cooked an opioid, it wasn’t to ease a back injury or chronic headaches. In an interview with NPR, he said he saw other people injecting, and it seemed like they were having a good time. He figured, why not?

He didn’t know his Indiana town of 4,500 people was in the midst of an HIV epidemic, so it never occurred to him to worry about sharing needles.

Over the past decade, the opioid epidemic in the United States has doubled the number of people injecting heroin, making the health risks associated with injection drug use a public health crisis.

During the same time period, the incidence of HIV has gone down, but as people like Devin share needles to inject drugs — particularly opioids — Stanford researchers are concerned that increased HIV transmission could be on the horizon.

Cora Bernard, a PhD student in Management Science and Engineering, led a study on prevention programs that could head off a resurgence of HIV and perhaps lessen the effects of the opioid crisis.

“There’s a real public health crisis associated with injecting,” said Bernard. “We think it’s important to understand what investments give highest value because HIV prevention programs, and especially programs that reduce the prevalence of injection drug use, can have outsized, positive impact on individuals, families and public safety.”

In July of 2016, Bernard and her co-authors published a different study examining pre-exposure prophylaxis (PrEP), a pill that reduces a person’s risk of infection when they come into contact with the HIV virus. They found that PrEP was effective, but expensive.

The new study examines alternatives that also reduce the risk of HIV infection but are more cost-effective. They created a model to determine how many quality-adjusted life years — a metric that incorporates both life expectancy and quality of life — a person could gain from four HIV prevention programs, and what those years would cost.

“The dynamics of HIV prevention and treatment are complex,” said Margaret Brandeau, PhD, the senior author of the study and a professor of Management Science and Engineering. “Our model allows us to evaluate the costs and effects of the interventions, singly and in combination, to determine what programs would be effective and cost-effective in preventing the spread of HIV among persons who inject drugs.”

Of the prevention programs simulated in the model, the authors found that opioid agonist therapy (OAT) was the most cost-effective. OAT replaces drugs like heroin with a prescription that provides similar effects under safer conditions.

Needle-syringe exchange programs (NSP) — in which people swap their dirty needles for clean ones — were the next most cost-effective option. This was followed by test-and-treat programs, which identify people with a high risk of contracting HIV, test them for the virus and treat them before the disease has much chance to spread — both within their own bodies and to others who are exposed.

The study estimated that PrEP can also successfully reduce HIV, but not in a cost-effective way. The authors write that the other three techniques could all cost less than $50,000 for each quality life year gained by individuals. PrEP would likely cost more than $600,000.

The prevention programs were most effective when used in combination. The authors project that combining OAT and NSP could avert up to 40,000 HIV infections over 20 years for people who inject drugs, not to mention preventing downstream sexual transmission of HIV to others.

According to Bernard, one of the benefits of OAT is that in addition to reducing the risk of HIV, it can also help people stop injecting drugs. The authors project that expanding OAT access could decrease the size of the injection population as much as 37 percent over 20 years.

“We started out thinking about this as an HIV problem, but we realized that the majority of health benefit actually comes from reducing injection drug use and improving quality of life for drug users,” said Bernard. “This is why we found OAT to be the highest-value investment.”

Bernard and her co-authors believe that employing techniques like OAT could help reduce the effects of the opioid crisis.

“Our study aims to help policy makers and clinicians understand how a variety of interventions can help improve health outcomes and prevent HIV,” said Douglas Owens, MD, an author of the study, a professor of medicine and an internist at the VA Palo Alto Health Care System. “We hope our analyses help show how to use limited resources efficiently to prevent the devastating consequences of substance use.”