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October 31, 2023

Limited availability of Nirsevimab in the United States

Interim CDC recommendations to protect infants from Respiratory Syncytial Virus (RSV) during the 2023–2024 respiratory virus season

Actions requested

  • Prepare to provide options to protect infants from respiratory syncytial virus (RSV) in the context of a limited supply of nirsevimab, a long-acting monoclonal antibody immunization product recommended for preventing RSV-associated lower respiratory tract disease in infants.
  • Follow CDC Interim recommendations for prioritizing available nirsevimab for the 2023–2024 RSV season.
    • Administer a 50mg dose for infants weighing <5 kilograms (<11 pounds). For infants born before October 2023, administer a 50mg dose of nirsevimab now. For infants born in October 2023, and throughout the RSV season, administer a 50mg dose of nirsevimab in the first week of life.
    • For infants weighing ≥5 kilograms (≥11 pounds), prioritize using a 100mg dose of nirsevimab for infants at highest risk of severe RSV disease:
      • Infants aged <6 months
      • American Indian and Alaska Native infants ages <8 months
      • Infants aged 6 to <8 months with conditions that place them at high risk for severe RSV disease
    • Suspend use of nirsevimab in palivizumab-eligible children aged 8–19 months per AAP recommendations.
    • Continue to offer nirsevimab to American Indian and Alaska Native children aged 8–19 months who are not palivizumab eligible.
    • Follow AAP recommendations for palivizumab-eligible infants aged <8 months when the appropriate dose of nirsevimab is not available.
    • To preserve supply avoid using two 50mg doses for children weighing >5 kilograms (≥ 11 pounds).
  • Encourage pregnant people to receive RSVpreF vaccine (Abrysvo, Pfizer) during 32 weeks' gestation through 36 weeks and 6 days' gestation to prevent RSV-associated lower respiratory tract disease in infants.
    • Only the Pfizer RSVpreF vaccine (Abrysvo) is approved and recommended for use in pregnant people. The GSK RSVpreF3 vaccine (Arexvy) should not be used in pregnant people.
      • Refer patients to Abrysvo Find a Vaccine to locate pharmacies and doctor's office that offer RSVpreF vaccine
    • Either RSVpreF vaccination or nirsevimab immunization for infants is recommended to prevent RSV-associated lower respiratory tract disease in infants, but administration of both products is not needed for most infants.
  • Continue to recommend and offer coadministration of vaccination against influenza and COVID-19 for all patients 6 months and older who are not up to date.
  • Remind patients that layered approaches including vaccination, masking, and improving ventilation remain critical to mitigating risk of COVID-19 and other respiratory viral infections, especially among high-risk individuals.
Prepare for stress on the healthcare system from increased hospitalizations related to respiratory infections.


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 (1, 2). RSV is the leading cause of hospitalization among U.S. infants (3). The highest incidence of RSV-associated hospitalization occurs in infants aged <3 months and then decreases with increasing age (4). 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.

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.