You could still OD, but it would not be a fentanyl OD, because the fentanyl in the drug would not be able to interact with the brain. If you took this vaccine,

You could still OD, but it would not be a fentanyl OD, because the fentanyl in the drug would not be able to interact with the brain. If you took this vaccine, it seems like you would be just as likely to OD from heroin as you would from fentanyl+heroin.