What is the recommended guidance for Respiratory Syncytial Virus (RSV) immunization?

RSV Immunization Guidance

All infants aged <8 months born during or entering their first RSV season should receive nirsevimab, a single-dose long-acting monoclonal antibody that has replaced palivizumab as the standard of care for RSV prevention. 1

Infants and Young Children: First RSV Season

Universal Recommendation for All Infants <8 Months

• Nirsevimab is recommended for all infants aged <8 months who are born during or entering their first RSV season, regardless of gestational age or underlying medical conditions. 1
• This represents a major shift from previous guidance that limited prophylaxis to only high-risk infants, as 79% of infants hospitalized with RSV have no underlying medical conditions. 1

Dosing by Weight

• 50 mg for infants weighing <5 kg (<11 lb) 1
• 100 mg for infants weighing ≥5 kg (≥11 lb) 1
• Only a single dose is needed for the entire RSV season. 1

Timing of Administration

• Administer from October through the end of March in most of the continental United States, ideally shortly before RSV season begins. 1
• Infants born shortly before or during RSV season should receive nirsevimab within 1 week of birth. 1
• Infants with prolonged birth hospitalizations should receive nirsevimab shortly before or promptly after hospital discharge. 1
• Use chronologic (not corrected) age for preterm infants to determine timing and eligibility. 1

Geographic Variations

• Tropical climates (southern Florida, Guam, Hawaii, Puerto Rico, U.S.-affiliated Pacific Islands, U.S. Virgin Islands) and Alaska have unpredictable RSV seasonality requiring consultation with local guidance. 1

Vaccine Coadministration

• Nirsevimab can be coadministered with routine childhood vaccines at different injection sites. 1
• Coadministration results in similar adverse event rates compared to vaccines alone and does not interfere with immune response. 1

Infants and Children: Second RSV Season (Ages 8-19 Months)

High-Risk Groups Requiring Nirsevimab

Nirsevimab (200 mg as two 100 mg injections at different sites) is recommended for children aged 8-19 months entering their second RSV season if they have: 1

• Chronic lung disease of prematurity requiring medical support (chronic corticosteroid therapy, diuretic therapy, or supplemental oxygen) within 6 months before RSV season 1
• Severe immunocompromise 1
• Cystic fibrosis with either:
  • Previous hospitalization for pulmonary exacerbation in first year of life or persistent chest imaging abnormalities, OR
  • Weight-for-length <10th percentile 1
• American Indian or Alaska Native ethnicity (due to 4-10 times higher RSV hospitalization rates in some populations) 1

Rationale for Limited Second-Season Use

• Children entering their second RSV season have substantially lower risk than first-season infants, making universal prophylaxis not cost-effective ($1,557,544 per quality-adjusted life year for general population). 1
• Nirsevimab replaces palivizumab for second-season high-risk groups and is expected to be cost-saving. 1

Historical Context: Palivizumab

When Palivizumab May Still Be Used

• Palivizumab is now largely replaced by nirsevimab but was previously the only option for RSV prophylaxis. 1
• Palivizumab requires monthly dosing (15 mg/kg IM) throughout RSV season (5 doses total), making it more burdensome than single-dose nirsevimab. 1, 2
• Palivizumab demonstrated 45-55% reduction in RSV hospitalization in clinical trials. 1, 3, 4

Palivizumab Limitations

• High cost and monthly administration requirement limited its use to <5% of all infants (only those with specific medical conditions). 1
• Must be given every 28-30 days during RSV season, with each dose providing approximately 1 month of protection. 2

Adult RSV Vaccination

Universal Recommendations

• All adults aged ≥75 years should receive a single dose of RSV vaccine regardless of comorbidities. 1, 5
• Adults aged 60-74 years should receive RSV vaccination if they have any risk factors for severe RSV disease. 1, 5
• Adults aged 50-59 years with risk factors should receive RSVPreF3 (Arexvy), the only vaccine approved for this age group. 6, 5

Risk Factors for Severe RSV Disease in Adults

• Chronic obstructive pulmonary disease (COPD) 5
• Asthma 5
• Heart failure or coronary artery disease 5
• Diabetes mellitus 5
• Chronic kidney disease 5
• Chronic liver disease 5
• Immunocompromise (including splenectomy) 6, 5
• Severe obesity (BMI ≥40 kg/m²) 5
• Neurologic/neuromuscular conditions affecting airway clearance 5
• Residence in nursing home or long-term care facility 1, 5

Adult Vaccine Characteristics

• A single lifetime dose is currently recommended with no booster doses. 6, 7, 5
• Administer between September and November, before RSV season begins. 6, 7, 5
• Can be coadministered with influenza vaccine at different injection sites. 6, 7, 5
• RSVPreF3 demonstrates 82.6% efficacy against RSV-associated lower respiratory tract disease with protection maintained for at least three seasons. 7, 5

Contraindications and Precautions

Absolute Contraindications

• History of severe allergic reaction (anaphylaxis) to previous dose or product component. 1

Precautions

• Children with bleeding disorders should receive nirsevimab following ACIP general best practice guidelines for immunization. 1
• Nirsevimab is not recommended for prevention of hospital-acquired RSV infection (no supporting evidence). 1

Important Clinical Pitfalls

• Do not withhold nirsevimab from infants who already had RSV infection—they should continue scheduled prophylaxis to prevent severe disease from new RSV infections. 2
• Previous RSV infection does not confer long-lasting immunity and does not contraindicate vaccination in adults. 7, 5
• Patient attestation is sufficient for documenting risk factors in adults; extensive medical documentation should not create barriers to vaccination. 5