mRNA Cancer Vaccines: A Critical Appraisal of Applications, Persistent Challenges and Realistic Future Perspectives

Abstract

Messenger RNA (mRNA) vaccines entered oncology on the strength of a technology validated at population scale for infectious disease prophylaxis, and the therapeutic cancer vaccine field has been reshaped accordingly. The platform permits rapid design-to-dose intervals, encoding of many epitopes within a single product, cell-free manufacture and a dosing schedule compatible with combination immunotherapy. Enthusiasm has nevertheless outpaced the maturity of the clinical evidence. This critical narrative review evaluates the strength, internal consistency and methodological quality of the literature on mRNA cancer vaccines, and distinguishes conclusions that are reasonably secure from those that remain provisional. Literature published between January 2005 and 13 June 2026 was identified through structured searching of biomedical and multidisciplinary scholarly indexes, supplemented by backward and forward citation tracing. Evidence was appraised for design adequacy, endpoint validity, sample size, control structure and consistency across independent groups, then organised thematically rather than study by study. Four conclusions are well supported. RNA constructs can reliably prime de novo, poly-epitopic CD4-positive and CD8-positive T cell responses against both shared and mutation-derived antigens in humans; vaccine-induced clones can persist for years; formulation and administration route govern the anatomical site of antigen presentation and the character of innate activation; and toxicity in the reported oncology cohorts has been predominantly low grade. Four conclusions remain insecure. Randomised evidence of clinical benefit rests on a single phase 2b melanoma trial whose primary comparison did not reach conventional significance; immunogenicity has been treated as an efficacy surrogate without formal validation; comparative data on antigen-selection strategies, delivery chemistries and dosing schedules are almost entirely absent; and the durability, cardiac and excipient-related safety questions raised by mass prophylactic use have not been examined in repeatedly dosed patients with cancer. Analysis of the reported discrepancies indicates that heterogeneity in neoantigen prediction pipelines, assay thresholds for defining an immune response, and tumour microenvironmental context explain much of the apparent inconsistency between trials. Priorities include randomised platform trials with harmonised immunological endpoints, head-to-head comparison of antigen and delivery strategies, and prospective surrogate-endpoint validation.