Understanding health and economic outcomes of HIV preexposure prophylaxis in people who inject drugs

People who inject drugs make up less than 1 percent of the U.S. adult population. But about 10 percent of new HIV infections in this country are attributable to injection drug use.

So it stands to reason that focusing on HIV interventions for drug users who get high through injection could have tremendous public health benefits, Stanford researchers contend in a study published in the Annals of Internal Medicine.

“We already know that the health benefits of interventions for high-risk individuals extend to the entire U.S. population,” said Cora Bernard, a PhD student in Management Science and Engineering at Stanford University and lead author of the paper, “Cost-Effectiveness of HIV Preexposure Prophylaxis for People Who Inject Drugs in the United States.”

“And with the recent surges in opiate drug use in the U.S. and HIV outbreaks in places like Scott County, Indiana, it’s increasingly important to invest in prevention programs that are both effective and cost-effective, ” Bernard said.

The authors used new clinical data to determine that pre-exposure HIV prophylaxis, combined with frequent screening and prompt treatment for those who do become infected, could reduce the HIV burden among those who inject drugs.

And that provides a public health benefit for all Americans.

”Value is an important consideration in health policy decisions that have substantial budget implications,” said Jeremy Goldhaber-Fiebert, an associate professor of medicine at Stanford and senior author of the paper.

However, prescription drugs costs in the United States are among the highest in the world, making this form of intervention quite expensive.

The U.S. Food and Drug Administration approved a daily combination of 300 mg of tenofovir disoproxil fumarate (TDF) and 200 mg of emtricitabine (FTC) for HIV-negative patients, at a cost of about $10,000 per patient a year.

Add to that the cost of the HIV screening and assessment for adverse effects every three months and monitoring for toxicities every six months.

“This kind of cost scales fast,” said Bernard. “Although you’d be preventing the downstream costs of some infections, providing PrEP to 25 percent of HIV-negative people who inject drugs for just one year would require an upfront investment of over $3 billion.”

“Our analysis highlights the importance of trying to provide this effective intervention less expensively,” noted Douglas K. Owens, MD, MS, of the VA Palo Alto Health Care System, and professor of medicine at Stanford. 

Successful Trials

Many trials have shown that daily oral pre-exposure prophylaxis (PrEP) — or taking HIV medications to reduce the chance of infection — can prevent heterosexual and same-sex transmission of HIV.

The Bangkok Tenofovir Study, the first randomized trial of PrEP for people who inject drugs, reported a 49 percent reduction in HIV infection in this high-risk population in Thailand.

The Centers for Disease Control and Prevention (CDC) revised its clinical practice guidelines in 2014 to recommend that PrEP be considered for any adult who injected drugs within the previous six months, shared needles, enrolled in drug dependence treatment, or was at increased risk for sexual transmission.

Although prior studies have explored the cost-effectiveness of PrEP for men who have sex with men, people who inject drugs differ in risk behaviors and HIV incidence. So the authors performed a model-based evaluation of the cost-effectiveness of expanding PrEP for people who inject drugs in the United States.

They incorporated new clinical trial results with epidemiologic and economic data to determine the optimal conditions under which pre-exposure interventions can be delivered to this high-risk population.

Their model captures sexual and injection transmissions between people who inject drugs, gay men, and all other U.S. adult heterosexuals between 2015 and 2035. The model includes opioid agonist therapy, such as methadone treatment, HIV screening and awareness, and antiretroviral treatment.

The authors found that PrEP along with frequent HIV screening and antiretroviral drugs for those who do become infected averted 26,700 infections and reduced HIV prevalence among people who inject drugs by 14 percent, compared to the current status quo. Achieving these benefits costs $253,000 per quality-adjusted life year (known as QALY, a common metric used to compare cost-effectiveness interventions.)

In comparison, needle-syringe exchange programs cost in the range of $4,500 to $34,000 per quality-adjusted life year.

Total expenditures for a PrEP program for this high-risk population could be as much as $44 billion over 20 years. This is equivalent to annually spending around 10 percent of the current federal budget for domestic HIV/AIDS on PrEP for people who inject drugs.

Is it worth it?

The authors concluded that frequent screening and pre-exposure prophylaxis, as well as prompt treatment for those who become infected, could reduce the HIV burden among people who inject drugs and provide substantial public health benefits.

They determined that enrolling 25 percent of HIV-negative people who inject drugs in a program that combined PrEP, screening and antiretroviral drugs would reduce the HIV burden in the United States.

But it is expensive.

“Cost effectiveness is only one of many considerations for policymakers, who must also evaluate the ethical dimensions of an HIV prevention program for a population with generally low access to health services,” the authors wrote.

However, given that there are other interventions for this population with demonstrated cost-effectiveness, they conclude that policymakers will want to consider the broad range of programs available for HIV prevention in this group.

The authors are now at work to directly compare PrEP with other prevention programs and identify cost-effective strategies for this high-risk population.

In an editorial that accompanies the paper, Rochelle P. Walensky, MD, MPH, a professor of medicine at Harvard Medical School, asks: “What good is preventing HIV if we do not first save that life at HIV risk?”

“As biomedical advances finally hold the promise of both effective HIV prevention and durable virologic suppression,” Walensky continues, “it may seem heretical to disfavor investments in PrEP for PWID. But now is the time to be maximally efficient (dare we say even frugal?) with HIV prevention resources to ensure their greatest impact, because the problems related to PWID (such as the immediate and high mortality associated with overdose) are far greater than the no-longer-deadly threat of HIV itself.”