Should a newborn receive two doses of an RSV vaccine?

RSV Prevention in Newborns: Single-Dose Strategy

Newborns do not receive two doses of RSV vaccine—they receive a single dose of nirsevimab (a long-acting monoclonal antibody) to protect them through their first RSV season. 1, 2

Primary Prevention Strategy for All Infants

• All infants younger than 8 months born during or entering their first RSV season should receive a single intramuscular dose of nirsevimab, which provides protection for the entire 5-month RSV season (typically October through March in most of the continental United States). 1, 3

• Nirsevimab is not a vaccine—it is a long-acting monoclonal antibody that provides immediate passive immunity, unlike vaccines that require the infant's immune system to generate a response. 1, 3

• The dosing is weight-based for the first RSV season: 50 mg for infants weighing less than 5 kg, and 100 mg for infants weighing 5 kg or greater, administered as a single intramuscular injection. 2

Timing of Administration

• Infants born during the RSV season (October–March) should receive nirsevimab within 1 week of birth, ideally during the birth hospitalization. 1

• Infants born outside the RSV season (April–September) should receive nirsevimab in October or November, just before the RSV season begins. 1

• Only one dose is needed per RSV season—there is no two-dose series for routine infant RSV prevention. 1, 2

Alternative Prevention: Maternal Vaccination

• Pregnant persons may receive RSVpreF vaccine (Abrysvo) as a single dose at 32–36 weeks' gestation to provide passive antibody protection to their infant through transplacental transfer. 1

• Either maternal RSV vaccination during pregnancy OR nirsevimab administration to the infant is recommended—not both for most infants. 1, 3 This is a critical point to avoid unnecessary duplication.

• Infants born to mothers who received RSV vaccination during a previous pregnancy (not the current pregnancy) should still receive nirsevimab, as maternal antibodies from prior pregnancies do not carry over. 1

High-Risk Infants in Their Second RSV Season

• Children aged 8–19 months at increased risk for severe RSV disease entering their second RSV season (including those with chronic lung disease requiring therapy, hemodynamically significant congenital heart disease, severe immunocompromise, or cystic fibrosis with severe lung manifestations) should receive 200 mg of nirsevimab administered as two separate 100 mg intramuscular injections at different sites. 1, 3, 2

• This is the only scenario where "two doses" are given, but it represents a single treatment episode (two injections simultaneously) for high-risk children in their second season, not routine newborn care. 2

Special Circumstances: Cardiac Surgery

• Infants undergoing cardiac surgery with cardiopulmonary bypass require an additional dose of nirsevimab as soon as they are medically stable after surgery, because bypass decreases serum nirsevimab levels. 2

• If surgery occurs within 90 days after receiving nirsevimab during the first RSV season, the additional dose should be weight-based (50 mg if <5 kg, 100 mg if ≥5 kg). 2

Efficacy of Single-Dose Strategy

• Nirsevimab demonstrates 79% efficacy in preventing medically attended RSV-associated lower respiratory tract infection and 80.6% efficacy in preventing RSV-related hospitalization. 3

• The single dose provides protection for approximately 5 months, covering the entire RSV season without need for monthly injections like the older palivizumab regimen. 3, 4

Common Pitfalls to Avoid

• Do not administer both maternal RSV vaccine and infant nirsevimab unless there are specific high-risk circumstances—this represents unnecessary duplication and is not recommended for most infants. 1

• Do not confuse nirsevimab with palivizumab—palivizumab required 5 monthly doses and is now reserved only for situations where nirsevimab is unavailable. 3

• Do not delay nirsevimab administration for infants born during RSV season—it should be given within 1 week of birth, ideally before hospital discharge. 1

• Do not use corrected gestational age for preterm infants—chronologic age determines eligibility and timing for nirsevimab. 1, 5

Coadministration with Routine Vaccines

• Nirsevimab can be administered simultaneously with routine childhood vaccines at the same visit using separate syringes at different injection sites. 1, 5, 2

• Do not mix nirsevimab with any vaccines or medications in the same syringe. 2