My point of confusion is still my initial question. It was actually the description of the mechanism, as given, that had me questioning it's effects on the overall toxicity/danger of ingesting the drug.
"Our vaccine is able to generate anti-fentanyl antibodies that bind to the consumed fentanyl and prevent it from entering the brain, allowing it to be eliminated out of the body via the kidneys. Thus, the individual will not feel the euphoric effects and can ‘get back on the wagon’ to sobriety,” said the study’s lead author Colin Haile"
They clarify that this causes a user to not feel the positive effects of the drug, but I would assume that if the drug was also able to prevent overall mortality, they would be excited enough to mention it.
To answer your question: yes, it does stop mortality. The general cause of death from opioid overdose is respiratory suppression when the brainstem is too “sedated” to continue sending signals to the rest of the body to breathe, so by stopping the fentanyl from entering the brain, this vaccine also blocks mortality.
Hard to do this justice without writing a full essay, but this vaccine need not be seen as an antabuse-like “restriction” on drug users. E.g. for the stereotypical* case of a user who unknowingly gets heroin cut with fentanyl, this would protect them from the fentanyl without blocking the euphoric effects of the heroin. Its most promising utility is in preventing users of other drugs from unintentional exposure to fentanyl via contaminated supply.
*(Yes, I know most street dope is Fentanyl-based these days.)
E: And to elaborate on why they might be putting emphasis on the fact it blocks the effects of fentanyl in their explanation, it might help prevent “unintended” addiction to fentanyl when users are unknowingly consuming it in conjunction with other drugs.
That's strange that they describe the selling point as being that you can't get high anymore. If it's really attacking and neutralizing the chemical per se, and if it's truly neutralized in every way, that would mean it would stop overdoses. That seems like a much bigger selling point.
If the vaccine only suppresses opioid euphoria, users would continue dosing assuming they needed a higher dose to feel the effects leading to overdose and have possible respiratory failure.
"Our vaccine is able to generate anti-fentanyl antibodies that bind to the consumed fentanyl and prevent it from entering the brain, allowing it to be eliminated out of the body via the kidneys. Thus, the individual will not feel the euphoric effects and can ‘get back on the wagon’ to sobriety,” said the study’s lead author Colin Haile"
They clarify that this causes a user to not feel the positive effects of the drug, but I would assume that if the drug was also able to prevent overall mortality, they would be excited enough to mention it.