Introduction to Palivizumab

Palivizumab is a humanized monoclonal antibody primarily used for the prevention of respiratory syncytial virus (RSV) infections in high-risk infants and young children. It was first approved by the FDA in 1998 and has since become a crucial tool in reducing RSV-associated hospitalizations in vulnerable pediatric populations.

Mechanism of Action

Palivizumab works by targeting the F protein on the surface of RSV. This protein is essential for viral entry into host cells and fusion between infected cells. By binding to the F protein, palivizumab prevents the virus from entering cells and spreading, effectively neutralizing its infectivity. This mechanism provides passive immunity against RSV infection.

Indications

Palivizumab is indicated for the prevention of serious lower respiratory tract disease caused by RSV in pediatric patients at high risk for RSV disease. The American Academy of Pediatrics (AAP) recommends its use in:

• Infants born before 29 weeks, 0 days gestation who are younger than 12 months at the start of RSV season
• Infants born before 32 weeks, 0 days gestation who are younger than 6 months at the start of RSV season
• Certain infants with chronic lung disease of prematurity or hemodynamically significant congenital heart disease
• Children younger than 24 months with profound immunocompromise during RSV season

Administration

Palivizumab is administered via intramuscular injection, typically in the anterolateral aspect of the thigh. The recommended dose is 15 mg/kg body weight, given once a month during the RSV season (usually November through March in the Northern Hemisphere). A maximum of 5 monthly doses is recommended for most indications.

Efficacy and Safety

Clinical trials have demonstrated the efficacy of palivizumab in reducing RSV-associated hospitalizations by approximately 45-55% in high-risk infants. The safety profile is generally favorable, with the most common side effects being fever and injection site reactions. Anaphylaxis and other severe hypersensitivity reactions have been reported rarely.

Special Considerations

- Cost-effectiveness: Due to its high cost, the use of palivizumab should be carefully considered based on risk factors and local RSV epidemiology.
- Resistance: While rare, RSV strains with reduced susceptibility to palivizumab have been reported. Ongoing surveillance is crucial.
- Storage: Palivizumab should be refrigerated at 2°C to 8°C (36°F to 46°F) and protected from light.
- Patient education: Caregivers should be informed that palivizumab does not prevent all RSV infections and the importance of maintaining good hygiene practices.