Аннотация:An editorial publication in the Science journal ("Preparing for" disease X, "Van Kerkhov et al. SCIENCE, •v. 374, Issue 6566,•p. 377 (2021)•DOI: 10.1126/science.abm7796) discusses how to be prepared for "Disease X." The revolutionary technology for the production of vaccines using mRNA opens endless possibilities for the fight against any infectious pathogens, in which the genetic information is recorded in RNA. Modern molecular biology, bioengineering, and bioinformatics can obtain the necessary information in days (hours) both about the structure of the pathogen mRNA (or mRNA fragment), sufficient to create the mRNA vaccine, and the method of its targeted delivery into the body.However, nucleic acids comprise four different nucleotides, while proteins constitute 20 various amino acids. Let a protein consist of 250 amino acids on average, and then the RNA encoding it contains 750 nucleotides. Let us assume that the specific recognition site by an antibody of both the RNA ribotope and the protein epitope consists of 10 structural elements (nucleotides, amino acids). Then, in the case of a protein, the sets of possible epitopes are 25, and the ribotopes are 75. The epitope consists of different 20 amino acids and the ribotope of 4 diverse nucleotides. At that instant, the variety of primary structures of all possible antigenic determinants in the case of such a protein will be 53130, and in the case of RNA, more than 86 million, according to a simple combinatorial formula. Thus, the selectivity of RNA recognition by the corresponding antibody is 1624 times less than that of the protein. In other words, the specificity of vaccines for proteins of pathogens (viruses) is more than one and a half thousand times higher than that of RNA vaccines.Generally accepted that RNAs are weak antigens in comparison with proteins. But not their complexes with proteins. In cells, RNAs form complexes with proteins. In this regard, the likelihood of undesirable formation of antibodies to RNA, undesirable due to the more remarkable similarity of the RNA composition of the pathogen and the host, compared to proteins, increases sharply.Potentially, this may pose a threat of interaction of antibodies to the pathogen RNA with the host's RNA. In turn, this can lead to autoimmune diseases. They develop slowly, but they are the most numerous. It is well known that antibodies to the host's RNA are found in the serum of patients with autoimmune diseases. The question arises, was the use of the mRNA vaccine justified? In a pandemic, without a doubt, YES! Summing up, we can conclude that vaccinations of people with coding mRNAs and preparations of biologically active nucleic acids require additional time for biomedical research.