There is now an additional option for the prevention of respiratory syncytial virus (RSV), the most common cause of hospitalization among infants and children in the United States. In July, the US Food and Drug Administration (FDA) approved nirsevimab, an RSV preventive monoclonal antibody, for use in neonates and infants born during or entering their first RSV season and in children up to 24 months of age who remain vulnerable to RSV during their second season.1 The Advisory Committee on Immunization Practices (ACIP) subsequently made 2 recommendations regarding use of nirsevimab, which I’ll detail in a moment.2
First, a word about RSV. The Centers for Disease Control and Prevention estimates that each year in children younger than 5 years, RSV is responsible for 1.5 million outpatient clinic visits, 520,000 emergency department visits, 58,000 to 80,000 hospitalizations, and 100 to 200 deaths.2 The risk for hospitalization from RSV is highest in the second and third months of life and decreases with increasing age.
There are some racial disparities in RSV severity, likely reflecting social drivers of health: ICU admission rates are 1.2 to 1.6 times higher among non-Hispanic Black infants younger than 6 months than among non-Hispanic White infants, and hospitalization rates are up to 5 times higher in American Indian and Alaska Native populations.2
What nirsevimab adds to the toolbox. Until recently, there was only 1 RSV preventive agent available: palivizumab, also a monoclonal antibody. The American Academy of Pediatrics has recommended palivizumab be used only for infants at high risk for RSV infection, due to its high cost and the need for monthly injections for the duration of an RSV season. In addition, the Academy has noted that palivizumab has limited effect on RSV hospitalizations on a population basis and does not appear to affect mortality.3
Nirsevimab has a longer half-life than palivizumab, and only 1 injection is needed for the RSV season. Early studies on nirsevimab demonstrate 79% effectiveness in preventing medical-attended lower respiratory tract infection, 80.6% effectiveness in preventing hospitalization, and 90% effectiveness in preventing ICU admission. The number needed to immunize with nirsevimab to prevent an outpatient visit is estimated to be 17; to prevent an ED visit, 48; and to prevent an inpatient admission, 128. Due to the low RSV death rate, the studies were not able to demonstrate reduced mortality.2
What the ACIP recommends. At a special meeting in July, the ACIP recommended 1 dose of nirsevimab for2:
- all infants younger than 8 months who are born during or entering their first RSV season
- children ages 8 to 19 months who are at increased risk for severe RSV disease and entering their second RSV season.
Those at risk include children with chronic lung disease of prematurity who required medical support any time during the 6-month period before the start of their second RSV season; those with severe immunocompromise; those with cystic fibrosis who have manifestations of severe lung disease or weight-for-length < 10th percentile; and American Indian and Alaska Native children.2
How to administer nirsevimab. The dose of nirsevimab is 50 mg IM for those weighing < 5 kg, 100 mg for those weighing ≥ 5 kg, and 200 mg for high-risk children entering their second RSV season.2 Nirsevimab can be co-administered with other recommended vaccines; however, both nirsevimab and palivizumab should not be used in the same child in the same RSV season.
Nirsevimab should be administered in the first week of life for infants born shortly before or during RSV season, and shortly before the season for infants younger than 8 months and those ages 8 to 19 months who are at high risk.4 The months of highest RSV transmission in most locations are December through February, but this can vary. Local epidemiology and advice from state and local health departments are the best source of information about when RSV season starts and ends in your area.
On the horizon. Nirsevimab will be included in the Vaccines for Children program and covered by commercial health plans with no cost sharing.5 A maternal vaccine to prevent RSV in newborns is likely to be approved by the FDA in the near future.