Introduction. The need to maintain a high level of vaccination coverage against measles, rubella and mumps in conditions of an increased risk of outbreaks of infections due to violations of vaccination tactics associated with the pandemic of coronavirus infection and due to the unfavorable epidemic situation in neighboring countries determines the advisability of using a combined vaccine for the simultaneous prevention of these three socially significant infections. The aim of the study: to analyze the quality of commercial series of a new domestic combined cultured live vaccine against measles, rubella and mumps (MRM) throughout the entire time of its manufacturing according to all specification indicators in regulatory documentation (RD). Materials and methods. The object of the study was the combined cultured live vaccine against measles, rubella and mumps. The analysis of the quality of the drug was carried out according to 86 consolidated production protocols of manufactured series, as well as according to the results of control of these series in the Testing Center for Quality Expertise of the Federal State Budgetary Institution NCESMP of the Ministry of Health of the Russian Federation. Results. It is shown that the quality of the combined drug for the prevention of measles, rubella and mumps corresponds to the RD in all studied indicators. The drug does not contain an antibiotic. Bovine serum albumin, which is a technological impurity, is detected in quantities more than 5 times lower than the established norm. A comparison of the specific activity of the viral components of new combined domestic vaccine and the components of the bivalent vaccine against measles and mumps produced by the company in 20192021 showed that the spread of the activity values of the viral components in the new drug and in the series of mumps-measles vaccine was minimal, which allowed us to make a conclusion about the stability of the production technology. Conclusion. The quality of the new domestic combined vaccine for the prevention of measles, rubella and mumps meets WHO requirements. The results of the conducted studies indicate the stability of production and the standard quality of the drug. The use of a combined vaccine against three significant infections will ensure the necessary level of vaccination coverage in the population. Information about the results of studies can help reduce the number of vaccination refusal.