Beyfortus (generic name: Nirsevimab) was approved by the United States Food and Drug Administration (FDA) on July 17, 2023. Beyfortus is a long-acting monoclonal antibody designed to protect newborns and infants from medically attended respiratory syncytial virus (RSV) infection. For the purposes of the Beyfortus drug trials, "medically attended" refers to any RSV infection requiring a doctor's visit in the office, urgent care, or hospital.
RSV is the most common cause of lower lung infections in children less than one year of age. These types of lung infections include bronchiolitis and/or pneumonia. Bronchiolitis often begins with a runny nose and cough, but can worsen to include a faster breathing rate, wheezing, crackles, and needing to work harder to breathe. Infants are at risk for developing apnea, which is defined as a temporary pause in breathing or the absence of breathing for greater than 20 seconds.

According to the Centers for Disease Control and Prevention (CDC), RSV causes approximately 2.1 million non-hospital doctor's office visits each year in children less than 5 years old1 as well as 58,000-80,000 hospitalizations each year in that same age group. (1,2,3) They report 100-300 deaths in children younger than 5 years due to RSV annually.4
Newborns and infants less than six months of age and those born prematurely (before 35 weeks gestation) are at the highest risk for having an infection severe enough to require hospitalization. These RSV infections usually require closely monitoring the young child's breathing. The hospitalized infant or child may need breathing support, medications, and intravenous (IV) fluid support during the worst portion of the illness.

Beyfortus was created to prevent severe RSV infection in infants during their first RSV season, when they are at the highest risk for complications from the virus. According to a press release from the manufacturer, Sanofi: "The single administration of Beyfortus was developed to correspond with the beginning of the RSV season for babies born prior to the season or at birth for those born during the RSV season. In clinical trials, Beyfortus helped prevent RSV LRTD [lower respiratory tract disease] requiring medical care in all infant populations studied, including those born healthy at term, late preterm or preterm, or with specific health conditions that make them vulnerable to severe RSV disease. RSV disease requiring medical care included physician office, urgent care, emergency room visits, and hospitalizations."5

The Advisory Committee on Immunization Practices (ACIP) and the American Academy of Pediatrics (AAP) are now recommending Beyfortus to all infants less than 8 months of age during or entering their first RSV season. The federal government has stepped in to cover the medication cost in out-of-hospital settings for children enrolled in the Vaccine for Children (VFC) Program. The VFC Program generally helps provide vaccines to children whose caregivers may not have been otherwise able to afford them. Private insurers have not determined how much of the purported $415 cost they plan to cover.

This leaves hospitals and private medical practices to determine how best to deploy this medication, which leads to concerns about access and equity. Providers offering the VFC-covered Beyfortus in their offices must also offer it to patients with private insurance. This means paying out anywhere from thousands to a million plus dollars to offer this medication. A cost that may not be recuperated by most hospitals or practices. The decisions will then likely be made on a local level whether or not to offer Beyfortus to any child, which will render distribution to be variable at best and to exclude those in less affluent areas at worst.

Beyfortus reduces the risk of RSV infection that requires medical attention by approximately 70-75% relative to placebo.6 Despite this data, the cost-benefit analysis needs to be taken seriously. For any parent with a sick or hospitalized child with RSV, there is no cost too high to prevent that illness. Hospitals nationwide are facing serious financial constraints, with access to care significantly strained, especially in rural areas. Earlier this year, a report from the Center for Healthcare Quality and Payment Reform highlighted the risk for additional hospitals to close in the near future: "More than 100 rural hospitals have closed over the past decade, and more than 600 additional rural hospitals — over 30% of all rural hospitals in the country — are at risk of closing in the near future. Rural hospitals are at risk of closure because they lose money delivering services to patients. In the past, many hospitals have received grants, local tax revenues, or subsidies from other businesses that offset these losses, but there is no guarantee that these funds will continue to be available or sufficient to cover the higher costs hospitals are experiencing. Millions of people could be directly harmed if these hospitals close."7

While the insurers, government, and medical providers consider these complex factors, RSV season is rapidly approaching. It is quite likely that the full implementation and availability of Beyfortus will not be appreciated during the upcoming RSV season.

Works Cited:

  1. Hall CB, Weinberg GA, Iwane MK, et al. The burden of respiratory syncytial virus infection in young children. New Engl J Med. 2009;360(6):588–98.
  2. Rha B, Curns AT, Lively JY, et al. Respiratory Syncytial Virus–Associated Hospitalizations Among Young Children: 2015–2016.Pediatrics. 2020;146(1):e20193611.
  3. McLaughlin JM, Khan F, Schmitt H-J, et al. Respiratory Syncytial Virus–Associated Hospitalization Rates among US Infants: A Systematic Review and Meta-Analysis. JID. 2022;225(6):1100-1111.
  4. Hansen CL, Chaves SS, Demont C, Viboud C. Mortality Associated With Influenza and Respiratory Syncytial Virus in the US, 1999-2018.JAMA Network Open. 2022 Feb 1;5(2):e220527.
  7. Saving Rural Hospitals - The Crisis in Rural Health Care (