Anti-drug vaccines as a harm reduction strategy: potential, limitations, and translational challenges

Abstract Background Substance use disorders (SUDs) continue to impose a major global public health burden, with persistently high relapse rates and barriers to sustained recovery. While traditional harm reduction strategies—such as opioid substitution therapy, needle exchange programs, and contingency management—have improved health outcomes, additional biomedical tools are needed. Immunotherapies, including anti-drug vaccines and monoclonal antibodies (mAbs), offer a novel adjunctive approach within the broader harm reduction framework. Main body Anti-drug vaccines stimulate the production of drug-specific antibodies that bind to psychoactive substances in the bloodstream, forming complexes too large to cross the blood–brain barrier. This may reduce reinforcement and limit intoxication. mAbs, by contrast, offer passive immunity and are being investigated for rapid-onset applications, including overdose mitigation. Preclinical and early-phase clinical trials targeting nicotine, cocaine, opioids, and methamphetamine have shown encouraging pharmacological effects. However, multiple barriers have impeded translation into practice, including interindividual variability in immune responses, short-lived antibody titers requiring boosters, behavioral compensation (e.g., dose escalation), and lack of sustained clinical efficacy in large trials. In addition, real-world implementation is limited by the absence of cost-effectiveness evaluations, regulatory ambiguity, and manufacturing complexity. Ethical issues, particularly regarding informed consent in justice-involved or marginalized populations, also warrant attention. Conclusion When integrated with behavioral, pharmacological, and psychosocial interventions, anti-drug immunotherapies may enhance the effectiveness of existing harm reduction strategies. Their potential lies not in replacing current approaches but in reinforcing them. Achieving this will require further clinical research, critical evaluation of past failures, and careful navigation of ethical, regulatory, and logistical challenges.