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October 25, 2023
These interim recommendations from CDC apply to healthcare settings with limited nirsevimab availability during the 2023–2024 RSV season. Interim recommendations are subject to change as new evidence becomes available.
RSV is a common cause of respiratory infection in U.S. infants, most of whom are infected with RSV during their first year of life. RSV is the leading cause of hospitalization among U.S. infants. The highest incidence of RSV-associated hospitalization occurs in infants aged <3 months and then decreases with increasing age. Because of the high incidence of severe RSV disease in the first months of life, RSV prevention products focus on passive immunization of young infants through maternal immunization or immunoprophylaxis with monoclonal antibodies.
In July 2023, the Food and Drug Administration (FDA) approved nirsevimab (BeyfortusTM, Sanofi and AstraZeneca), a long-acting monoclonal antibody, for passive immunization to prevent RSV-associated lower respiratory tract disease among infants and young children. On August 3, 2023, CDC’s Advisory Committee on Immunization Practices (ACIP) recommended nirsevimab for all infants aged <8 months who are born during or entering their first RSV season and for infants and children aged 8–19 months who are at increased risk for severe RSV disease and are entering their second RSV season. The recommended dosing of nirsevimab for infants weighing <5 kilograms (kg) (<11 pounds (lb)) is 50mg. For infants aged <8 months weighing ≥5 kg (≥11 lb), the recommended dose is 100mg. For infants aged 8–19 months at increased risk of severe RSV disease entering their second season, the recommended dose is 200mg. Nirsevimab is supplied in single-dose prefilled syringes of either 50mg or 100mg. Cost of a nirsevimab prefilled syringe is the same for a 50mg dose or a 100mg dose.
Current reports to the National Respiratory and Enteric Virus Surveillance System (NREVSS), a national laboratory-based surveillance network, indicate RSV transmission has increased to seasonal epidemic levels in the Southern regions of the United States and is expected to continue to increase in the rest of the country within the next 1–2 months.
For the 2023–2024 RSV season, the manufacturer reports a limited supply of nirsevimab, particularly the 100mg dose prefilled syringes used for infants weighing ≥5 kg. Based on manufacturing capacity and currently available stock, there are not sufficient 100mg dose prefilled syringes of nirsevimab to protect all eligible infants weighing ≥5 kg during the current RSV season. Additionally, supply of the 50mg dose prefilled syringes may be limited during the current RSV season. CDC continues to work with the manufacturer to understand how it may accelerate nirsevimab supply.
See full CDC HAN Health Alert for additional information and references