Micro-RNAs (miR) are non-coding RNA filaments that control mRNA transcription. Micro-RNAs have been studied in cancer pathogenesis, metastasization, cancer therapy, the structuring of the central nervous system, diabetes, and heart disease. Mir-134-138 regulate the development of dendritic spines needed for synapses. Their silencing can lead to autistic spectrum disorders and mental retardation and damage to brains in evolution such as childhood and adolescence, producing learning problems and mood problems, and in adults for alterations of receptors for neurotransmission. It has been shown that N1-methyl pseudouridine binds to miR and induces silencing processes, increasing cell methylome at the origin of cancer. The production of mRNA vaccines replaces Uridine with N1-methyl-pseudouridine to escape innate immunity and implement rapid translation. N1-methyl-pseudouridine binding with mi-RNA alters the epigenetic transcription of oncosuppressor that, with the increase in cell methylation, could result in the induction of tumors and relapses, natural immunity inhibition, and neuro-behavioral disorders transmissible to progeny. Vectorial vaccines hybridize the host DNA with adenoviruses and induce tumors at the experimental level. Clinical reports and long-term epidemiological investigations are necessary to verify the impact of mRNA vaccines on health.