Preterm infants born before the 35th week of gestation are at high risk of severe respiratory syncytial virus (RSV) infection. Passive immunoprophylaxis with palivizumab, a monoclonal antibody against RSV, is currently recognized as the most effective measure to prevent RSV infection. The objective of the study was to evaluate the efficacy of prophylactic use of palivizumab in premature infants at high risk of severe RSVI. Patients and methods. A single-center retrospective cohort study conducted on the basis of the Catamnesis Cabinet of the Republican Clinical Perinatal Center (Ufa) included 516 premature children with gestational age less than 35 weeks who reached the age of 1 year of life from April 2020 to April 2022. 250 children were included in the "immunization+" group, and 266 children were included in the "immunization-" group. In both groups, the proportion of children who went to the outpatient clinic for acute respiratory infection (ARI) and the proportion of children hospitalized for lower respiratory tract infection (LRTI) were determined. Results. Among the immunized, the proportion of children presenting to the outpatient clinic for ARI was lower than among the non-immunized, 63.6% and 82.0%, respectively (p < 0.001; OR 0.77; 95% CI 0.69-0.86). There was no statistically significant reduction in the rate of hospitalization of preterm infants due to LRTI overall. However, the proportion of children hospitalized for bronchitis was lower among the immunized than among the non-immunized, 24.0 and 31.6%, respectively (p = 0.045; HR 0.74; 95% CI 0.55-0.99). The greatest effect of palivizumab immunization was observed in children born at 32 weeks' gestation or less who received 3-5 injections of the drug. Conclusion. This study demonstrated the efficacy of immunoprophylaxis with palivizumab in premature infants of the first year of life from the high-risk group of severe RSVI. Key words: respiratory syncytial virus, acute respiratory infection, hospitalization, premature infants, high-risk group, immunoprophylaxis, palivizumab