Background: Respiratory Syncytial Virus (RSV) infection is the leading cause of hospitalization in infants below age 12 months and highest below age 6 months. Despite considerable evidence on the clinical predictors of RSV hospitalizations, little is known about their cost, its drivers and their relation to age and season.

Results: With 51,645 estimated annual hospitalizations in infants <12 months, rates of RSV hospitalization (RSVH) by age were highest for infants 1 month of chronological age (2.42 times the annualized average) and declined steadily thereafter. The percentage of RSVH with MV declined from months <1 to 4, with subsequent fluctuations (Fig 1A).  Charges per RSVH exceeded the annual average only for infants aged <1 and 1 month (Fig 1B).  In 2020 prices, RSVH charges per episode averaged $175,211 with MV vs. $17,313 without MV, totaling $1.51 billion annually for the birth cohort of 4.04 million infants ($374 per infant).  As only 4.5% of RSVHs had MV, those without MV comprised 67.5% of aggregate yearly charges.  RSVHs were highly seasonal, with the rate in the highest month (Feb) 110 times that in the lowest month (July). However, utilization of MV (Fig 2A) tended to be lower in the RSV season. While average RSVH charges were higher outside the RSV season, their seasonal pattern was similar for admissions with and without MV (Fig 2B). MV utilization depended mostly on age (Fig 3).

Conclusions: RSV in infants under one year generate substantial hospital charges.  While each infant receiving MV is expensive, infants with MV are not the main driver of costs.  Rather, the large number and share (95.5%) of hospitalizations without MV is the major determinant of aggregate charges.