Nirsevimab Cuts RSV Risk in Healthy Newborns: Daily Dose

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On July 25, 2025, we reported on a study published in the journal Pediatrics that examined the effectiveness of nirsevimab against polymerase chain reaction (PCR)-confirmed respiratory syncytial virus (RSV)-related lower respiratory tract disease (LRTD) among healthy term infants and RSV-associated health care utilization.

The study

Investigators conducted a real-world analysis at Kaiser Permanente Northern California (KPNC) of 31 900 healthy term infants born between April 2023 and April 2024. Of the total cohort, 15 647 infants (49.1%) received nirsevimab. Infants whose mothers received maternal RSV vaccination or who had underlying high-risk conditions were excluded from the analysis.

The findings

Among infants who received nirsevimab, there were 35 episodes of RSV LRTD (6.10 per 1 000 person-years) compared with 462 episodes (58.51 per 1 000 person-years) in the nonimmunized group. The adjusted effectiveness of nirsevimab against RSV LRTD was 87.2% (95% CI, 81.7–91.1; P < .001).

Effectiveness against hospitalized RSV LRTD was even higher at 98.0% (95% CI, 85.1–99.7; P < .001). Additionally, nirsevimab was associated with a 71.0% (95% CI, 65.3–75.8; P < .001) reduction in PCR-confirmed RSV infection of any severity.

Authors' comments

"These findings support the Advisory Committee on Immunization Practice’s recommendation for eligible infants aged < 8 months entering their first RSV season to receive nirsevimab to reduce the risk of RSV infection."

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