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Here’s a clear comparison between palivizumab and nirsevimab for RSV (respiratory syncytial virus) prevention in infants — what they are, how they differ, and where each fits in current practice:
🧬 What They Are
Palivizumab is a humanized monoclonal antibody targeting the RSV fusion (F) protein, designed to prevent severe RSV infection in high-risk infants. It’s been used since the late 1990s. (Wikipedia)
Nirsevimab is a next-generation long-acting monoclonal antibody that also targets the RSV F protein (especially the prefusion conformation) but has been engineered for a much longer duration of action. (FRCPath Prep Microbiology)
⏱️ Duration & Dosing
| Feature | Palivizumab | Nirsevimab |
|---|---|---|
| Half-life | ~20–30 days (short) (Wikipedia) | ~70–150 days (extended) (FRCPath Prep Microbiology) |
| Dosing schedule | Monthly intramuscular injections throughout RSV season (~5 doses) (contemporarypediatrics.com) | Single dose per RSV season (FRCPath Prep Microbiology) |
| Typical protection period | ~1 month per dose | Covers entire RSV season with one dose (FRCPath Prep Microbiology) |
Bottom line: nirsevimab offers a single seasonal dose vs palivizumab’s multiple monthly injections.
👶 Who They’re For
Palivizumab has been traditionally used for high-risk infants:
• Preterm babies
• Chronic lung disease of prematurity
• Congenital heart disease
and in some cases during a second RSV season if still high risk. (contemporarypediatrics.com)Nirsevimab is now being used more broadly:
• All infants in their first RSV season — regardless of risk factors in many countries (e.g., UK, US recommendations) (FRCPath Prep Microbiology)
• Continued use in certain high-risk infants in second season as per local guidelines (Indian Health Service)
In some health systems (e.g., UK/NHS), nirsevimab replaces palivizumab for eligible infants due to wider applicability and simpler dosing. (RCPCH Learning -)
📈 Effectiveness
Palivizumab has consistently shown reductions in RSV-related hospitalisations (~45–55% in high-risk groups). (NCBI)
Nirsevimab has demonstrated strong protection against severe RSV outcomes, with real-world data showing ~80% effectiveness against RSV-associated ICU admission and acute severe disease in infants. (CDC)
Laboratory studies also show that nirsevimab generates higher and longer-lasting neutralising antibody levels than palivizumab. (Pediatrics Publications)
💉 Safety & Practical Considerations
Both are generally well-tolerated monoclonal antibodies with similar side effect profiles (e.g., injection site reactions). (contemporarypediatrics.com)
Palivizumab’s monthly injections can be burdensome for families and healthcare systems. Nirsevimab’s single dose is more convenient and may improve adherence. (This vs. That)
💡 Key Takeaways
✅ Palivizumab: long-established, used mainly for very high-risk infants, requires multiple doses. (contemporarypediatrics.com)
✅ Nirsevimab: newer, long-acting, often recommended for all infants in the first RSV season with one dose, broadly replacing palivizumab in many settings. (FRCPath Prep Microbiology)
✅ Nirsevimab’s practical advantages (single dose, longer protection) and strong clinical effectiveness make it a major advance in RSV prevention. (CDC)
If you want, I can also explain how maternal RSV vaccines compare to these monoclonal antibodies in protecting newborns.
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