Table 2.

Monoclonal Antibody (Nirsevimab) Efficacy

Outcome	Efficacy 0–150 d After Administration [% (95% Cl)]
RSV-associated ICU admission*	90.0 (16.4–98.8)
Hospitalization for RSV-associated LRTI†	80.6 (62.3–90.1)
Medically attended RSV-associated LRTI‡	79.0 (68.5–86.1)

RSV, respiratory syncytial virus;ICU, intensive care unit; LRTI, lower respiratory tract infection.

^*Intensive care unit admission for an LRTI associated with a positive RSV polymerase chain reaction (PCR) test result. LRTI was defined as one or more documented physical examination findings localizing to the lower respiratory tract (rhonchi, rales, crackles, or wheeze), one or more clinical sign of severity (increased respiratory rate [age younger than 2 months, 60 breaths/minute or more;age 2–6 months, 50 breaths/minute or more;age more than 6 months to 2 years, 40 breaths/minute or more];hypoxemia [on room air]: oxygen saturation below 95% at altitudes of 1,800 m or less or below 92% at altitudes more than 1,800 m;acute hypoxic or ventilatory failure;new-onset apnea;nasal flaring;retractions [intercostal, subcostal, or supraventricular retractions];grunting;dehydration attributable to respiratory distress).

^†A medically attended visit for a respiratory tract infection (defined as at least one of the following: nasal discharge for 24 hours or more; difficulty breathing, labored breathing, or rapid breathing;cough;inability to feed because of respiratory symptoms;apnea;other respiratory symptom of concern) and an RSV-positive test result for an infant with one of the following indicators of a severe LRTI: increased respiratory rate (70 breaths/minute or higher in infants younger than age 2 months, 60 breaths/minute or higher in infants aged 2–12 months, 50 breaths/minute or higher in children aged 12–24 months), oxygen saturation less than 93%, use of high-flow nasal cannula or mechanical ventilation, admission to the ICU for 4 or more hours, or lack of response or unconsciousness.

^‡A medically attended visit for a respiratory tract infection (as defined above) and an RSV-positive test result for an infant with one of the following indicators of an LRTI: increased respiratory rate (60 breaths/minute or higher in infants younger than age2 months, 50 breaths/ minute or higher in infants aged 2–12 months, 40 breaths/minute or higher in children aged 12–24 months), oxygen saturation less than 95%, or chest wall indrawing