Sept. 15, 2021 -- Opioid-related drug overdose deaths in the United States exploded to an estimated record high of 69,031 people in 2020, topping the 49,860 deaths logged in 2019, according to a new report from the CDC. Most of the deaths involved synthetic opioids such as fentanyl.
President Joe Biden has pledged more than $10 billion to expand access to prevention, treatment and recovery services. The money is important as people receiving treatment for opioid use disorder have a high risk for relapse, and that means a high risk for opioid overdose.
Now, researchers are studying a possible bridge to successful recovery: A vaccine that could blunt the drugs' ability to cause harm.
The first such vaccines are now entering clinical trials, raising hopes of adding another tool to the anti-addiction armamentarium. But even if the vaccines prove safe and effective, their success could generate some new problems to solve.
An advantage of vaccines is that their effects can last for several months, says trial investigator Sandra Comer, professor of neurobiology and psychiatry at Columbia University Irving Medical Center. Dropout rates for existing medical therapies for opioid use disorder are as high as 50% at 6 months, and a vaccine could protect people from overdose and give them time to re-enter treatment.
"It serves as a bit of a safety net," she says.
The first vaccine to enter a trial targets oxycodone. Volunteers are being recruited who have a diagnosis of opioid use disorder but are not being medically treated and are still using opioids. A third of them will receive a placebo vaccine, a third will receive a low-dose injection of vaccine, and the other third will receive a high-dose vaccine.
A Shot Against Oxycodone
Researchers are primarily tracking the safety of the shot, but they're also looking at whether vaccination prevents the euphoria that opioids usually produce. They expect to enroll 24 people initially but expand to 45 if results look promising.
In response to the shot, the body produces antibodies, proteins that tag oxycodone and keep it from reaching the brain. If the drug can't reach brain cells, it can't produce euphoria. And more important for lifesaving effects, it can't block the brain's signals to the body to breathe. The vaccine has already performed well in animal studies.
Previous trials of vaccines for cocaine and nicotine failed. Those vaccines made it to the last clinical trial stage, but didn't prove effective overall. So this time, investigators plan to track antibody levels in participants, examining blood samples for signs of a good immune response to the vaccine.
But even though earlier cocaine and nicotine vaccines didn't work for everybody, there were some people they seemed to help. This is why investigators involved in opioid vaccine trials want to track immune responses, says Marco Pravetoni, associate professor of pharmacology and medicine at the University of Minnesota Medical School, whose team will be assessing the blood samples. Ultimately, he says, a doctor might even be able to use this information to tailor vaccine selection to a specific person.
Pravetoni also says that oxycodone is one of three vaccine targets — the other two are heroin and fentanyl — that researchers hope to combine into a single shot. Recipients might need to have one shot a month for the first 3 to 4 months and then receive annual boosters.
Stopping the Pain
The vaccines also raise some issues that need attention, says Cody Wenthur, assistant professor of pharmacy at the University of Wisconsin, who is not involved in the vaccine trials.
"If you're vaccinated against oxycodone, you might not have access to adequate pain control if you get into a car accident, for example," he says.
Clinicians could use other opioids for pain management, but limiting the opioids that the vaccine targets is a "double-edged sword," says Wenthur, because vaccinated people could just switch their opioid of choice to one that a vaccine does not inhibit.
Although these issues need to be addressed, vaccines, if successful, will have an important role. Wenthur notes a survey of pharmacists and pharmacy students that he and his group conducted showing that respondents "overwhelmingly" viewed a potential vaccine as helpful.
If the vaccines do become available, their application could extend beyond people who have opioid use disorder, says Pravetoni. He mentions the 2002 incident when terrorists took over a theater in Moscow and Russian special forces are thought to have used an aerosolized form of fentanyl to incapacitate everyone in the room. More than 100 of the hostages died, and the episode raised the specter of opioids being used in chemical attacks. Pravetoni says vaccination could offer protection for first responders, law enforcement or other people whose professions place them at risk for inhalation, either accidentally or through such attacks.
These or other real-world applications for people at risk for exposure are several years away. Pravetoni says it took 10 years to get to this phase and estimates that in about 5 years, a vaccine that targets multiple opioid drugs might enter the first clinical trial.