The opioid use disorder is a significant public health concern in the United States. There have been a large number of opioid overdose deaths and as a result, a public health emergency was declared in October 2017. This growing number of overdose deaths can in part be attributed to the increased frequency of fentanyl contamination in the United States heroin supply. Previously, our research group has published several examples of immunotherapy as an innovative treatment strategy for substance use disorders. This strategy provides immunoantagonistic protection from the drug without interacting with the drug’s target receptor(s). Moreover, antidrug vaccines produce a long-lasting blockade against the target drug without any of the side effects. Our research group has already developed heroin vaccine and fentanyl vaccine. In our efforts to further combat the opioid crisis as well as tackle the rampant emergence of fentanyl in the United States heroin supply, we questioned whether a heroin-fentanyl dual vaccine could be feasible. We examined the effects of “admixture vaccine of fentanyl and heroin hapten immunoconjugates” and “chemically contiguous heroin-fentanyl hapten conjugated vaccine” as dual vaccines against heroin contaminated with fentanyl. Herein, we detail the preparation of these vaccines and their biological evaluation.