CDC: Limited Supply of RSV Immunization Nirsevimab


The federal agency sent out a health advisory to change the prescribing recommendations for the newer preventative respiratory syncytial virus (RSV) monoclonal antibody.

This week the Centers for Disease Control and Prevention (CDC) sent out a health advisory letting the public and clinicians know there is a limited supply of nirsevimab-alip (Beyfortus, Sanofi AstraZeneca), a long-acting monoclonal antibody immunization product recommended for preventing RSV-associated lower respiratory tract disease in infants.1

According to the CDC, for this year’s RSV season, the federal agency is now recommending prioritizing available nirsevimab 100mg doses for infants at the highest risk for severe RSV disease which include:

  • young infants (age <6 months) and;
  • infants with underlying conditions that place them at highest risk for severe RSV disease.1

Recommendations for using 50mg doses remain unchanged at this time, and they recommend avoid using 2 50mg doses for infants weighing ≥5 kilograms (≥11 pounds) to preserve supply of 50mg doses for infants weighing <5 kilograms (<11 pounds). Providers should be aware that some insurers may not cover the cost of two 50mg doses for an individual infant.1

In addition, CDC also said in the advisory that clinicians suspend using nirsevimab in palivizumab-eligible children aged 8–19 months for the 2023–2024 RSV season. These children should receive palivizumab per American Academy of Pediatrics (AAP) recommendations.1

CDC wrote in the health advisory that nirsevimab should continue to be offered to American Indian and Alaska Native children aged 8–19 months who are not palivizumab-eligible and who live in remote regions, where transporting children with severe RSV for escalation of medical care is more challenging or in communities with known high rates of RSV among older infants and toddlers. And prenatal care providers should discuss potential nirsevimab supply concerns when counseling pregnant people about RSVpreF vaccine (Abrysvo, Pfizer) as maternal vaccination is effective and will reduce the number of infants requiring nirsevimab during the RSV season.1

Nirsevimab Approval

The FDA approved nirsevimab in July and it is indicated for the prevention of RSV lower respiratory tract disease (LRTD) in newborns and infants born during or entering their first RSV season, and for children up to 24 months of age who remain vulnerable to severe RSV disease through their second RSV season.

“RSV can cause serious disease in infants and some children and results in a large number of emergency department and physician office visits each year,” John Farley, MD, MPH, director of the Office of Infectious Diseases in the FDA’s Center for Drug Evaluation and Research, said in a statement at that time. “Today’s approval addresses the great need for products to help reduce the impact of RSV disease on children, families and the health care system.”

Nirsevimab is a single-dose monoclonal antibody provided directly to newborns and infants, and offers rapid protection to help prevent LRTD caused by RSV, without requiring activation of the immune system. The administration can be timed to the start of the RSV season.

The FDA's Antimicrobial Drugs Advisory Committee (AMDAC) voted to recommend the approval of nirsevimab in June.

What the Data Showed
The phase 3 MELODY trial (Trial 04) was a randomized, double-blind, placebo-controlled trial conducted across 21 countries designed to determine the safety and efficacy of nirsevimab against medically attended LRTD caused by RSV in healthy term and late preterm infants (35 weeks gestational age or greater) entering their first RSV season, including efficacy against severe disease such as hospitalization, through 150 days after dosing. The primary endpoint was met, reducing the incidence of medically attended RSV LRTD by 74.9% (95% CI 50.6, 87.3; P<0.001) compared to placebo. The efficacy of nirsevimab against the secondary endpoint of hospitalization was 60.2% (95% CI: -14.6, 86.2).


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. CDC. October 23, 2023. Accessed October 25, 2023.

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