In 2021, the drug epidemic in America hit a grim milestone, with more than 100,000 overdose deaths—more than in any prior year. Two-thirds of those deaths were a result of synthetic opioids, like fentanyl—a drug that’s up to 50 times stronger than heroin.
Fentanyl has been a driving force of the opioid epidemic, and that crisis is expected to only get worse. But a new vaccine in development at the University of Houston aims to help those who are addicted by blocking fentanyl from entering their brain or spinal cord, preventing the drug’s euphoric effects, and, ultimately, averting an overdose or relapse.
“Typically we make vaccines against bugs—viruses and bacteria. This is unique, making a vaccine that produces antibodies that bind to a drug,” says Colin Haile, a research associate professor of psychology at the University of Houston and a founding member of the UH Drug Discovery Institute. Haile also directs and coordinates the experiments for the fentanyl vaccine research, which has been in the works for about seven years and is funded by the Department of Defense.
The vaccine works by producing antibodies that bind to fentanyl when the drug is ingested, preventing it from affecting the central nervous system. A recent paper published in the journal Pharmaceutics showed that the vaccine was effective in lab rats, and didn’t cause any adverse side effects.
To Haile, the target population for a fentanyl vaccine would be those who want to get sober. “They’re usually on maintenance therapy such as buprenorphine, but a very, very high percentage of these individuals with opioid use disorder relapse,” he says.
Part of the recovery for someone with an opioid addiction may include taking buprenorphine or methadone, so-called maintenance treatments that can be used for months and minimize withdrawals or cravings. But even after treatment, people often relapse; in fact, opioid addiction sees a relapse rate as high 80%. “When [patients] do relapse, if they’re vaccinated, they will not feel the euphoric effects of the drug, and hopefully get back on the wagon to sobriety,” Haile says.
Maintenance therapy as well as overdose prevention options also rely on treatments to block or partially block opioid receptors; buprenorphine, which is taken as a tablet, binds to opioid receptors and does not fully activate them, and can be taken as a treatment for dependence. Naloxone, which can be administered as a nasal spray or injection, does the same, reversing or blocking the effects of opioids, but is given to someone who shows signs of an overdose. Those therapies don’t trigger the immune system like this new vaccine would.
Dominic Sisti, an associate professor in the Department of Medical Ethics & Health Policy at the University of Pennsylvania, who was not involved with the fentanyl vaccine research, called this work “incredible and innovative.” Still, he notes that the function of “blocking the high” can be achieved with other interventions, and isn’t a silver bullet to solving the crisis of drug addiction.
Sisti notes that social and environmental pressures also play a role in addiction, which focusing solely on a drug’s impact on the brain, or treating addiction like a disease, fails to address. “Addiction is not just about the high,” he says. “There’s so much about addiction that we chalk up now to brain-based, disease model of addiction, and it’s much more complicated than that.”
Substance abuse has been put in a category known as “diseases of despair,” which Sisti says is a critical way to look at this issue: “Why are people despairing so much?” A vaccine that blocks the effects of fentanyl is a “tertiary prevention mechanism,” he says. “This is like putting up fences on bridges to prevent suicide. . . . It’s preventative of an overdose, but it’s not preventative of addiction.”
In that way, he’s hesitant to call it a vaccine, and notes it’s more of a fentanyl blocker. “As another tool in the tool box, that’s a good thing,” he says. “But we just don’t want to lose sight of the larger picture here, and maybe think about ways to get folks help before they get to the place where they need a quasi vaccine for addiction.”
Sisti does believe this development could help save lives, particularly of people with severe addiction. But as with any drug treatment, it has to be applied in the right context. A 2012 paper Sisti coauthored on the ethical questions of a cocaine vaccine noted that “drug vaccines”—of which there has already been research into many, including cocaine, heroin, methamphetamines, and morphine—come with ethical questions around potentially forcing these treatments into parole programs or for those who were incarcerated for drug use. The paper argued that use of a vaccine that prevents the effects of one drug could also trigger “a replacement drug market,” wherein someone who is addicted to that substance simply turns to another drug.
The fentanyl vaccine does not bind to other opioids, Haile says, meaning individuals that receive a vaccine would still feel the effects of morphine, methadone, oxycodone, and so on. While that means they may also turn to those drugs, it also means that if they need such pain treatment, the vaccine wouldn’t block those other opioids.
Haile from the University of Houston adds that whether or not this vaccine is the right path for someone looking to overcome their addiction is a question for their treatment team and physician, and may not be for everyone. If someone were to get the vaccine, they would get an initial dose and then two boosters. It’s not clear yet how long the effects would last; in rats, boosters were given at three and six weeks, with “complete blockade effects” lasting 20 weeks. (Haile says the effects could potentially last longer, but the testing was stopped at 20 weeks because of funding constraints.)
Haile and his team have started manufacturing a clinical-grade vaccine that will be used in toxicology studies and then, hopefully, human clinical trials. He expects to get approval from the Food and Drug Administration—in part because the vaccine’s components are used in two other vaccines that have been on the market for years—and then embark on clinical trials. “We’re getting close,” he says, “and it’s an exciting time.”
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