New advances in RSV: Is prevention attainable?

Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infection (LRTI), hospitalization, and mortality in infants and young children globally. The greatest burden of severe disease and mortality occurs in low-middle income countries (LMICs), with large and vulnerable childhood populations. The highest rates of RSV-hospitalization occur in healthy-term infants under 3 months of age. Preterm infants, children with chronic lung disease of prematurity, Down's syndrome, congenital heart disease, or immunodeficiency also have a higher risk of severe RSV-LRTI. Early-life RSV-LRTI has also been associated with chronic sequelae, including recurrent LRTI, recurrent wheezing, asthma, and lung function impairment. A RSV pre-fusion (F) maternal vaccine and long-acting monoclonal antibody (nirsevimab) have been licensed for the prevention of RSV-LRTI in infants and young children. Studies show high efficacy and effectiveness particularly for preventing severe RSV-LRTI. Maternal RSV vaccine given at 24-36 weeks of pregnancy was effective in preventing RSV medically attended LRTI and severe RSV-LRTI through 6 months after birth in a phase 3 study conducted in 18 countries over two RSV seasons. Vaccination was safe with no significant difference in adverse events between infants born to mothers who received RSV preF vaccine compared to placebo. A numerical imbalance in preterm births that occurred predominantly in South Africa, unrelated to vaccine timing or gestational age at vaccination and unassociated with mortality, coincided with COVID-19 delta and omicron waves. Nirsevimab, given as a single dose prior or during the RSV season, had high efficacy in preventing RSV-LRTI hospitalization in infants in preterm and in full-term infants, as well as in young children with underlying conditions through 150 days post administration in phase 2 and 3 trials. High effectiveness against hospitalization or severe disease in infants and in at-risk children up to 2 years of age has also been reported in several countries where implementation has occurred. RSV-LRTI is now a preventable disease in infants and young children. Rapid implementation of these highly effective interventions has occurred in many high-income countries, but access remains very limited in LMICs. Access to such RSV preventive interventions is urgently needed for all children to strengthen child health and promote global equity.