Objective: To evaluate the impact of immunoprophylaxis with Palivizumab in preterm infants of less than 35 weeks in terms of hospitalization rate, intensive care unit requirement, and mortality.

Methods: A prospective cohort study was conducted in preterm infants who received at least one dose of Palivizumab during the first six months. The primary outcome was the hospitalization rate related to RSV infection.

Results: 222 newborns participated in the study; 91.8% completed the six-month follow-up. 88.7% received a second dose of palivizumab, 79.7% a third dose, 34.7% a fourth dose, and 25.2% a fifth one. The non-adjusted incidence rate of RSV infection was 2.4%, the overall RSV-positive hospitalization rate was 1.9%. The proportion of patients that required NICU and mechanical ventilation in relation to RSV infection was 1.4%. Discharge with home oxygen, pulmonary dysplasia, and being younger than six months were significantly associated with respiratory infection. Likewise, being exposed to cigarette smoke was the only factor associated with increases risk of hospitalization. The group that required hospitalization received fewer doses of Palivizumab (p=0.049). No discontinuation of treatment due to adverse events were reported. No death was judged to be related to Palivizumab.

Conclusion: The hospitalization rate and the need for NICU admission were lower than those reported in the literature. In this real-life setting, Palivizumab appears to be effective in preventing serious cases of RSV infection.