CDC Advises on Limited Nirsevimab Supply and RSV Protection Options


The Centers for Disease Control and Prevention is advising providers to prioritize 100 mg doses of nirsevimab, a monoclonal antibody FDA-approved to prevent respiratory syncytial virus (RSV), for infants at the highest risk of severe RSV disease.

Doctor vaccinating baby in clinic: © Marina Demidiuk -

Doctor vaccinating baby in clinic: © Marina Demidiuk -

(Editor's note: A version of this article originally appeared on our sister website, Contemporary Pediatrics).

In an effort to address the challenges arising from a restricted availability of nirsevimab, an FDA-approved monoclonal antibody developed by Sanofi and AstraZeneca for safeguarding infants from respiratory syncytial virus (RSV)-related lower respiratory tract disease (LRTD), the Centers for Disease Control and Prevention (CDC) has issued a Health Alert Network Health Advisory, exploring alternative methods of shielding against RSV.

A surge in demand for nirsevimab, as described by Sanofi, has led to a shortfall of this vital resource for the upcoming 2023-2024 RSV season. Collaborating with the CDC, Sanofi is striving to ensure an equitable distribution of available doses through the Vaccines For Children Program (VFC). Consequently, the CDC recommends that priority be given to the available 100 mg nirsevimab doses, specifically for infants at the highest risk of experiencing severe RSV disease.

Nirsevimab's approval extends to newborns and infants under one year old, who are either born during their first RSV season or entering it, and to children up to 24 months old who remain susceptible to severe RSV during their second RSV season. The CDC underscores that infants under six months of age and those with underlying health conditions are especially vulnerable to severe RSV disease.

The CDC underscores that the usage of 50 mg doses remains unchanged. Moreover, the agency advises against administering two 50 mg doses to infants weighing 11 pounds or more (equivalent to 5 kilograms or more) to ensure that an adequate supply of 50 mg doses remains available for infants under 11 pounds.

For the 2023-2024 RSV season, the CDC recommends providers to suspend the use of nirsevimab in palivizumab-eligible children aged 8 to 19 months. However, nirsevimab should continue to be offered to American Indian and Alaska Native children in the same age group who are not eligible for palivizumab and reside in remote areas.

Sanofi has stated that it is actively collaborating with AstraZeneca, the manufacturer responsible for producing nirsevimab, to expedite additional supply and explore various measures to expand the production network of this prescription medicine.

To address concerns about nirsevimab supply, healthcare providers are encouraged to discuss the RSVpreF maternal vaccine (Abrysvo; Pfizer) when counseling pregnant individuals. The maternal vaccine has the potential to reduce the number of infants requiring nirsevimab during the RSV season. Approved by the FDA in August 2023, RSVpreF has demonstrated a 57% reduction in the risk of RSV-associated hospitalizations for infants during their first six months after birth. In September 2023, the CDC recommended administering one dose of this vaccine during weeks 32 through 36 of pregnancy for pregnant individuals.

1. 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. Centers for Disease Control and Prevention. Press release. October 23, 2023. Accessed October 26, 2023.,risk%20for%20severe%20RSV%20disease.

2. Sanofi Beyfortus statement. Sanofi. Press release. Accessed October 26, 2023.

3. Fitch. J. CDC recommends Pfizer’s maternal RSV vaccine to protect newborns. Contemporary Pediatrics. September 25, 2023. Accessed October 26, 2023. Link

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