The odds of a child inheriting a cancer-causing gene defect from a parent are roughly 50%, and 5–10% of all cancers are inherited. Fortunately, when early preventative measures are taken, cancer can be nipped in the bud. However, preemptive cancer treatment is still an emerging field, and there exist very few minimally-invasive options that have entered clinical use. Our research aims to develop a preventative mRNA vaccine against the CT83 antigen, a highly tumour-specific Cancer Testis Antigen. CT83 is very commonly hypomethylated, and hence overexpressed in gastric cancer, lung adenocarcinoma, and breast cancer. To produce the vaccine, we used CT83 mRNA from gastric cancer cells. We purified this mRNA and encapsulated it in a lipid nanoparticle, before transfecting HEK 293T epithelial cells with our vaccine. We then extracted the cellular mRNA, and carried out a qPCR to check for changes in expression of CT83. Our vaccine induced a 284-fold increase in CT83 expression in the HEK 293T cells, which suggests that our vaccine works to induce CT83 transcription. Future studies could aim to explore whether the increase in CT83 expression induced by our vaccine would lead to an immune response through testing for expression of CT83 epitopes, in-vitro testing and detection and mapping of T-lymphocyte activity. When proven functional, this vaccine could be used as preemptive personalised medical treatment for people who are genetically more predisposed to develop CT83-related cancers, and could also be the dawn of a new era in immunotherapy where it could serve to enhance patients’ intrinsic immune responses against existing cancer. This could potentially save one million lives annually worldwide.