Respiratory Syncytial Virus (RSV) is associated with most of the acute viral respiratory tract infections causing hospitalization with a peak during the first months of life. Many clinical trials of RSV vaccine candidates are being carried out. The aim of this study was to obtain epidemiologic information to give suggestions on target populations and prevention strategies before the introduction of new vaccines or monoclonal antibodies. We retrospectively evaluated, over a 5-year period (September 2014–August 2019), a population of hospitalized Italian children aged 0–6 years with a laboratory confirmed diagnosis of RSV infection. Risk factors, seasonality of RSV infection, distribution according to age, cases of coinfections and reinfections and cases needing Intensive Care Unit were evaluated. Hospitalizations due to RSV were 624 in the period under study. The peak was found between November and April, with 80.4% of cases recorded between December and February. 62.5% of cases were found in children under three months of age and 41% in children under 30 days old. The need for intensive care was associated with younger ages, with 70.9% of cases in children below three months of age. Unless the incoming vaccines demonstrate a strong herd protection effect, preventive strategies should be aimed at newborns or at maternal immunization.

Background: Respiratory Syncytial Virus (RSV) is the primary cause of respiratory infections and hospitalizations in young children globally, leading to substantial disease burden and mortality. The aim of the present study was to review and provide updates on how the SARS-CoV-2 pandemic have significantly influenced RSV epidemiology on hospitalized children due to RSV infection. A potential impact of the available preventive strategies on the same population were provided.Methods: All children aged 0–6 years hospitalized at Meyer Children’s Hospital IRCCS for RSV infection from September 2014 to March 2023 were retrospectively recorded. Seasonal trends before and after SARS-CoV-2 pandemic, age distribution, ICU admission and co-infections, comorbidities and prematurity were retrieved. Predictions on the number of hospitalizations avoided by the deployment of different preventive strategies were provided.Results: A total of 1,262 children with RSV infection were included in the study. The 70% of them had less than 1 year-of-age at the moment of hospitalization and almost 50% less than 3 months. In the post-pandemic seasons, a 317% increase in the number of hospitalizations was recorded with a significant increase in older children compared to the pre-pandemic seasons. ICU support was required for 22% of children, the majority of whom were under 3 months of age. Almost 16% of hospitalized children were born preterm and only 27% of hospitalized children had prior comorbidities. The rate of comorbidities among RSV hospitalized children increased with age. Nirsevimab prophylaxis could have prevented more than 46% of hospitalizations in this cohort. A preventive strategy addressing also children aged 7 months to 6 years of age with co-existing comorbidities would increase that rate above 57%.Discussion: The identification of RSV hospitalization-related features is informing the decision-maker for the deployment of the wisest preventive approach on a population scale.

Human respiratory syncytial virus (hRSV) is a significant cause of respiratory tract infections, particularly in young children and older adults. In this review, we aimed to comprehensively summarize what is known about the immune response to hRSV infection. We described the innate and adaptive immune components involved, including the recognition of RSV, the inflammatory response, the role of natural killer (NK) cells, antigen presentation, T cell response, and antibody production. Understanding the complex immune response to hRSV infection is crucial for developing effective interventions against this significant respiratory pathogen. Further investigations into the immune memory generated by hRSV infection and the development of strategies to enhance immune responses may hold promise for the prevention and management of hRSV-associated diseases.

Background: Respiratory Syncytial Virus (RSV) is the leading cause of hospitalizations in infants. The approval of nirsevimab, a long-acting monoclonal antibody, has extended the potential for RSV prophylaxis to all infants. This study assesses the cost–benefit of various Nirsevimab prophylaxis strategies for infants during their first RSV season in preventing RSV-associated hospitalization in the Tuscany region, Italy.Methods: The analysis was conducted from the perspective of the healthcare payor. Real-world data from the Tuscany birth cohort (N = 21,017) experiencing their first RSV season in the 2023/2024 season were used to calculate the net benefit and benefit cost ratio (BCR) of three possible nirsevimab prophylaxis strategies compared with prophylaxis practices at the time of the study, which includes the use of palivizumab in eligible infants. RSV-associated hospitalizations and severe hospitalizations were considered as health outcomes. Sensitivity analyses were performed to identify influential variables.Results: Under prophylaxis practices at the time of the study, there were a total of 663 hospitalizations associated with RSV, including 102 severe cases, representing €5,247,645 in costs. An extended prophylaxis strategy with nirsevimab, including all infants born both before and during the RSV season, resulted in the highest number of hospitalizations avoided (378), with a BCR close to break-even (0.96). A seasonal-only strategy targeting infants born during the season prevented the fewest hospitalizations (252), showing a positive BCR of 1.15. Finally, a seasonal strategy with targeted catch-up, including also preterm infants born before the season, yielded the highest cost–benefit ratio (1.56), preventing 270 hospitalizations.Conclusion: Universal prophylaxis strategies with nirsevimab, targeting all infants during their first RSV epidemic season, substantially reduce hospitalization burdens without increasing economic pressure on the healthcare system. Although alternative strategies are more cost-effective, they prevent fewer hospitalizations, emphasizing the public health value of broader prophylaxis approaches.