One shot, two seasons: How Beyfortus is reshaping RSV protection for infants

A single dose of Beyfortus, the monoclonal antibody injection used to prevent respiratory syncytial virus in infants and young children, can reduce lower respiratory tract infection hospitalizations by more than half through a second RSV season, according to large-scale longitudinal research. The findings follow a sharp drop in infant hospitalizations during Korea's first full season after the drug's introduction and are fueling calls for systemic support to make universal prevention accessible to all young children.

Health authorities in Spain's Galicia region — the first in the world to incorporate Beyfortus into a national immunization program — have been tracking infants who received the injection since September 2023. The large-scale longitudinal study, which runs through October 2026, analyzed infection and hospitalization data from the first RSV season (2023–2024) through the end of the second (2024–2025).

Infants who received Beyfortus had an 85.9% lower rate of RSV-related lower respiratory tract infection hospitalizations in the first season compared with a historical control group. Even in the second season — when no additional dose was given — the reduction held at 55.3%. The findings provide meaningful evidence that a single dose can deliver sustained protection through an infant's second RSV season, at least for healthy, full-term babies without underlying conditions.

RSV infects more than 90% of children under 2 and is a leading cause of acute respiratory illness in infants. When the virus progresses to lower respiratory tract infections such as bronchiolitis or pneumonia, hospitalization becomes necessary, placing a significant burden on families. Because it is impossible to predict which infants will develop severe illness, universal prevention for all young children is considered essential.

Beyfortus launched in Korea in February last year and demonstrated its effectiveness during the country's first six-month RSV season after its introduction. According to sentinel surveillance data from the Korea Disease Control and Prevention Agency (KDCA), RSV hospitalizations among infants fell about 60% from their peak compared with the previous year, confirming the drug's clinical utility in real-world settings.

Health professionals advise that the timing and eligibility criteria for the injection be clearly understood and applied. Healthy, full-term infants born between October and March — the peak RSV season — should receive a single dose within one week of birth, while those born between April and September should receive it just before the season begins. High-risk infants under 2 with underlying pulmonary or cardiac conditions, or those born prematurely, are advised to receive an additional dose just before their second RSV season.

Yoon Ki-wook, a professor in the division of pediatric infectious diseases at Seoul National University College of Medicine, said RSV is the most common cause of lower respiratory tract infections in infants and young children, and that prevention is paramount given the absence of a treatment. "As domestic and international data and Spain's long-term research demonstrate, prevention strategies targeting high-risk groups are well justified in terms of reducing medical costs and protecting the health of young children," he said. He added that he hopes Korea will "swiftly establish an institutional environment where infants and young children can be safely protected from infectious diseases without economic barriers, as has been demonstrated abroad."