FDA Approves First Vaccine Against RSV in Neonates, Babies up to Age 24 Months

The US Food and Drug Administration on Monday approved the first vaccine against respiratory syncytial virus (RSV) lower respiratory tract disease (LRTD) for newborns and infants born during or entering their first RSV season, according to an agency news release.¹ The monoclonal antibody nirsevimab (Beyfortus; Sanofi and AstraZeneca) is also indicated to protect children up to 24 months of age who remain vulnerable to severe RSV through their second season.¹

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The companies said that the nirsevimab launch in planned to precede the 2023-2024 RSV season.

Nirsevimab was designed to protect a broad infant population, according to an AstraZeneca (AZ) statement,² including healthy neonates born at term, or preterm, or with specific health conditions that place them at high risk for RSV LRTD. It is given as a single intramuscular injection at birth or at the start of the RSV season for those born during the months when RSV circulation is high, typically beginning in the fall and peaking in the winter months.²

Approximately 1% to 3% of US children younger than age 12 months are hospitalized because of RSV each year, said the FDA.¹ Most infants will experience mild cold-like symptoms, but others can develop LRTDs like pneumonia and bronchiolitis, which can lead to emergency department visits. The highest risk for severe RSV is among infants born prematurely and with chronic lung disease of prematurity or significant congenital heart disease.¹

“Today’s approval marks an unprecedented moment for protecting infant health in the US, following an RSV season that took a record toll on infants, their families, and the US healthcare system,” Thomas Triomphe, Sanofi executive vide president said in the statement.² “Beyfortus is the only monoclonal antibody approved for passive immunisation to provide safe and effective protection for all infants during their first RSV season.”²

The vote in June by the FDA’s Antimicrobial Drugs Advisory Committee (AMDAC) on the positive nirsevimab benefit/risk profile was unanimous, according to AZ, and was based on 3 pivotal clinical trials.²

The key efficacy measure, the incidence of medically-attended RSV LRTD, was evaluated for 150 days after administration of the vaccine.

In a phase 2 trial (NCT02878330), 1453 preterm infants (born at at least 29 weeks but less than 35 weeks of gestation) that were born into or entering their first RSV season were included. Of the full cohort, 963 received a single dose of nirsevimab and 484 received placebo. Results showed that 25 (2.6%) nirsevimab-treated infants experienced medically attended RSV LRTD vs 46 (9.5%) infants who received placebo. Relative to placebo, nirsevimab reduced MA RSV LRTI risk by approximately 70%.¹

In the phase 3b Hospitalized RSV Monoclonal Antibody Prevention (HARMONIE; NCT05437510) study, which recruited more than 8000 participants, nirsevimab demonstrated an 83.21% reduction in RSV-related hospitalizations in infants younger than age 12 months who received a single dose of nirsevimab-alip, compared to infants with no RSV intervention.³

A phase 2/3 palivizumab- (Synagis, Arexis A/B) controlled trial assessed safety and tolerability of nirsevimab in preterm (<35 weeks gestation) infants and infants with congenital heart and/or chronic lung disease of prematurity.This study's data on the vaccine’s safety and pharmacokinetic profile provided the evidence for its use to prevent medically attended RSV LRTD in this vulnerable population.¹

Nirsevimab was well tolerated across all clinical trials with a consistent safety profile, said the FDA. Adverse events, noted as mild or moderate in severity, occurred at a similar rate with nirsevimab and placebo; the most common were rash and injection site reactions.¹

Nirsevimab comes with precautions and warnings regarding serious hypersensitivity reactions, including anaphylaxis, according to the FDA. Nirsevimab-alip should be given “with caution to infants and children with clinically significant bleeding disorders,” the FDA stated.¹

References

1. FDA approves new drug to prevent RSV in babies and toddlers. FDA. Press release. July 17, 2023. Accessed July 17, 2023. https://www.fda.gov/news-events/press-announcements/fda-approves-new-drug-prevent-rsv-babies-and-toddlers

2. Beyfortus approved in the US for the prevention of RSV lower respiratory tract disease in infants. AstraZeneca. July 17, 2023. Accessed July 18, 2023. https://www.astrazeneca.com/media-centre/press-releases/2023/beyfortus-approved-in-the-us-for-the-prevention-of-rsv-lower-respiratory-tract-disease-in-infants.html

3. Codson N. Nirsevimab gets FDA advisory committee recommendation to prevent RSV in infants. Patient Care Online. June 9, 2023. Accessed July 18, 2023. https://www.patientcareonline.com/view/nirsevimab-gets-fda-advisory-committee-recommendation-to-prevent-rsv-in-infants