INTRODUCTION: Rubella virus has pronounced teratogenic properties that can cause generalized and persistent intrauterine infection of the fetus. As a result, the control of the loss of teratogenicity inherent in «wild-type¼ virus strains is a necessary stage of a preclinical study of the vaccine strain for a live attenuated rubella vaccine.The purpose of the study is to comprehensively study the teratogenic properties of the vaccine strain of rubella virus «Orlov-V¼ in the experiment on rhesus macaques. MATERIAL AND METHODS: Seronegative to rubella virus female rhesus macaques in early pregnancy at the age of 4-7 years (n = 13) were used in the experiment. Animals of the experimental group (n = 9) received single immunization intramuscularly with a preparation from the «Orlov-V¼ strain. The control group of the monkeys (n = 3) were immunized with a commercial vaccine containing Wistar RA27/3 strain. The female of the control group (n = 1) was injected with a solvent used in the rubella vaccine. Study of possible teratogenic properties of vaccine strains of rubella virus was carried out using a complex of clinical, immunological, pathomorphological and virological methods. Clinical observations were made within 3 months after the monkeys' birth. Determination of antibody titers in the blood serum of immunized monkeys was performed in HI test on the 28th-30th day after infection. The ELISA method was applied to determine IgM antibodies in the blood serum of newborns within the first month of life. Detection of rubella virus RNA was performed by PCR with electrophoretic detection of amplicons. RESULTS: No markers of congenital rubella infection were found in infants born from monkeys vaccinated during the pregnancy. It is shown that PCR can be an informative method to confirm the absence of teratogenic properties of vaccine strains of rubella virus. DISCUSSION: The obtained data demonstrated that vaccine strains of the «Orlov-V¼ rubella virus and Wistar RA27/3 have lost their teratogenic properties. The possibility of using an alternative strategy for preclinical assessment of specific safety of antiviral vaccines including a complex of clinical, immunological, pathologic and virological methods instead of the classical pathologic method is discussed. CONCLUSION: The results obtained in this study showed the absence of teratogenic properties and high immunogenic activity of the vaccine strain of rubella virus «Orlov-V¼.