Nirsevimab, the First Monoclonal Antibody Approved for All Infants

Column Author: Maria Martinez, RN, BSN, MSN, MBA, CPN | Immunization Coordinator

Column Editor: Angela Myers, MD, MPH | Pediatric Infectious Diseases; Division Director, Infectious Diseases; Medical Director, Center for Wellbeing; Professor of Pediatrics, University of Missouri-Kansas City School of Medicine; Clinical Assistant Professor of Pediatrics, University of Kansas School of Medicine

This is it – the opportunity to protect infants from respiratory syncytial virus (RSV), the leading cause of hospitalization among U.S. infants.¹ Each year in the United States, RSV leads to 2.1 million outpatient (non-hospitalization) visits, 58,000-80,000 hospitalizations and 100-300 deaths in children under the age of 5.² After U.S. Food and Drug Administration (FDA) approval of nirsevimab in July 2023, many immunization professionals eagerly listened to the Advisory Council on Immunization Practices (ACIP) meeting on Aug. 3, 2023. You could hear the excitement in the room as the Vaccines for Children (VFC) resolution was approved and the votes for first season and second season (for high-risk groups) immunization passed for the first monoclonal antibody approved for all infants. The projected rollout for nirsevimab is early October.

In evaluating the approval of nirsemivab, the FDA and Centers for Disease Control and Prevention’s ACIP reviewed study data from multiple study sites. Clinical studies demonstrated sustained efficacy against RSV lower respiratory tract infection (LRTI) lasting five months.³

For infants aged <8 months in the clinical study group, efficacy through five months in preventing visits for RSV-associated LRTI was 79.0% (95% CI + 68.5%- 86.1%: 31 of 2,579 in nirsevimab arm and 80 of 1,293 in placebo arm). Efficacy in preventing hospitalization for RSV-associated LRTI was 80.6% (95% CI = 62.3%–90.1%; 12 of 2,579 in nirsevimab arm and 33 of 1,293 in placebo arm). Finally, efficacy in preventing intensive care unit admission for RSV-associated LRTI was 90.0% (95% CI = 16.4%–98.8%; one of 2,579 in nirsevimab arm and six of 1,293 in placebo arm). There were no deaths attributable to RSV in either trial.⁴

Another study was completed in infants at increased risk for severe RSV disease with 615 preterm infants and 310 infants with chronic lung disease. The patients were randomized to receive either nirsevimab or palivizumab. In lieu of true efficacy data, pharmacokinetic data were used to evaluate nirsevimab. Serum concentration levels of nirsevimab in children aged ≤24 months with chronic lung disease or congenital heart disease entering their second RSV season were comparable to levels for those who received nirsevimab in their first RSV season.⁴

Indications for administration of nirsevimab are as follows:

• Administration for infants aged <8 months born during or entering their first RSV season (typically October through March but may vary by region).
  • Administration dose:
    • Infants weighing <5 kg will receive one dose of 50 mg (0.5 ml) purple prefilled syringe⁷
    • Infants weighing ≥5 kg will receive one dose of 100 mg (1 ml) light blue prefilled syringe⁷
  • Those born immediately prior to or during RSV season should receive nirsevimab within one week of birth either at the birth hospital or in the outpatient setting.
• Administration for infants aged 8-19 months at increased risk for severe RSV disease and entering their second RSV season:
  • Administration dose:
    • Administer one dose, 200 mg, administered as two 100 mg injections given at the same time at different injection sites
  • Children at increased risk for severe disease who are recommended to receive nirsevimab when entering their second RSV season include:
    • Children with chronic lung disease of prematurity who required medical support (chronic corticosteroid therapy, diuretic therapy or supplemental oxygen) any time prior to six months from the onset of the second RSV season
    • Children who are severely immunocompromised
    • Children with cystic fibrosis who have either:
      • Manifestations of severe lung disease (previous hospitalization for pulmonary exacerbation in the first year of life or abnormalities on chest imaging that persist when stable)

OR

• Weight-for-length <10th percentile

• American Indian or Alaska Native children as data for these populations suggest the incidence of RSV-associated hospitalization for children aged 12-23 months was four to 10 times higher than that of similar-aged children.⁴

By 2 years of age, most children have already been exposed to RSV and have some immunity.⁵

To protect our families, we will need to be able to educate them on what this product is and why it’s recommended. When educating all staff and families, we should share that antibodies are part of our immune system that help protect us against infections. Monoclonal antibodies provide passive immunity by mimicking the antibodies that our bodies normally produce when exposed to an infection.⁶

In preparation for this new product, the American Academy of Pediatrics suggests considerations for practices and organizations, some of which include: determining the right amount of stock to order, assessing interest from families in the product, determining the cost of buying the immunization and potential storage constraints.⁷

At last, the wait is over. While it will come with some operational challenges, we now have a product that can help provide a form of protection to our youngest patients and put many families’ worries at ease.

References:

1. Smith Rogers L. The latest in RSV protection for kids: an antibody treatment called Beyfortus. Johns Hopkins Bloomberg School of Public Health. July 27, 2023. Accessed August 30, 2023. https://publichealth.jhu.edu/2023/beyfortus-provides-rsv-protection-for-kids
2. RSV surveillance and research. Centers for Disease Control and Prevention. Last reviewed July 17, 2023. Accessed August 30, 2023. https://www.cdc.gov/rsv/research/index.html
3. S. CDC Advisory Committee unanimously recommends routine use of Beyfortus™ (nirsevimab-alip) to protect infants against RSV disease. News release. Sanofi. Accessed August 30, 2023. https://www.sanofi.com/en/media-room/press-releases/2023/2023-08-03-19-21-36-2718475
4. Jones JM, Fleming-Dutra KE, Prill MM, et al. Use of nirsevimab for the prevention of respiratory syncytial virus disease among infants and young children: recommendations of the Advisory Committee on Immunization Practices — United States, 2023. MMWR Morb Mortal Wkly Rep. 2023;72:920–925. https://www.cdc.gov/mmwr/volumes/72/wr/mm7234a4.htm
5. Katella K. New monoclonal antibody and vaccine can protect kids from RSV. News release. Yale Medicine. August 28, 2023. Accessed August 30, 2023. https://www.yalemedicine.org/news/new-rsv-monoclonal-antibody-vaccine-for-kids
6. CDC recommends a powerful new tool to protect infants from the leading cause of hospitalization. News release. Centers for Disease Control and Prevention. August 3, 2023. Accessed August 30, 2023. https://www.cdc.gov/media/releases/2023/p-0803-new-tool-prevent-infant-hospitalization-.html
7. American Academy of Pediatrics. Nirsevimab (Beyfortus) product & ordering information. aap.org. Last updated September 12, 2023. Accessed August 31, 2023. https://www.aap.org/en/patient-care/respiratory-syncytial-virus-rsv-prevention/nirsevimab-beyfortus-product--ordering-information/