Background: RSV’s impact on infants, especially among vulnerable populations, is significant, but there are gaps in our understanding of RSV epidemiology. Using nationally representative inpatient data, this study describes RSV and bronchiolitis hospitalization (RSVH, BH) burden and rates in US infants by insurance payer, from 2011-2018.

Methods: Infant RSVH and BH were assessed using ICD codes in NIS, the largest publicly available all-payer database in the US. RSVH and BH burden and rates (/1,000 live births) were also described by insurance payer. For RSV, ICD-9 codes were 079.6, 466.11, and 480.1; ICD-10 codes were B97.4, J12.1, J20.5, and J21.0. Bronchiolitis included all RSV codes plus ICD-9 466.19 and ICD-10 J21.8 and J21.9. To calculate rates, 2011-2018 US live births data from the National Center for Health Statistics were used as the denominator. Chi-square test was done to evaluate Medicaid hospitalization rates to those of other insurance payers.

Results: From 2011-2018, annual average weighted infant RSVH and BH were 55,980 (range: 43,845-66,155) and 91,410 (range: 77,150-104,735) (Tables 1 and 2). The overall annual average RSVH and BH rates were 14.3 (95% CI: 13.7-14.8) and 23.3 (95% CI: 22.4-24.2) per 1,000 live births.

Analyses by payer demonstrated that Medicaid infants had the highest burden and rate of disease. Annual average weighted RSVH was highest for Medicaid infants compared to private and other/unknown infants (35,068 Medicaid (range: 27,105-42,185) vs. 17,943 private (range: 14,130-20,165) and 2,969 other/unknown (range: 2,545-3,805), respectively) (Table 1). A similar pattern was seen for the annual average weighted BH with Medicaid infants having the highest burden (59,039 Medicaid (range: 49,680-68,650) vs. 27,674 private (range: 23,100-30,335) and 4,697 other/unknown (range: 4,260-5,750) (Table 2). From 2011-2018, Medicaid infants have the highest RSVH burden (n=280,543 Medicaid vs. 143,547 private and 23,751 other/unknown) and the highest BH burden (n=472,310 Medicaid vs. 221,396 private and 37,576 other/unknown).

Medicaid infants also have the highest annual average RSVH rate (Medicaid: 22.0 [95% CI: 21.1-22.9] per 1,000 live births vs. private: 10.1 [95% CI: 9.7-10.5] and other/unknown: 5.4 [95% CI: 5.1-5.7]; p<0.0001) (Table 1) and the highest BH rate (Medicaid: 37.1 [95% CI: 35.5-38.6] per 1,000 live births vs. private: 15.5 [95% CI: 14.9-16.2] and other/unknown: 8.6 [95% CI: 8.0-9.1]; p<0.0001) (Table 2).

Conclusion: These nationally representative estimates demonstrate that Medicaid infants have twice the burden and risk of RSVH and BH compared to privately insured infants. Given the lack of systematic laboratory testing, RSVH burden and rate in US infants are likely to be underestimated with the use of ICD diagnosis codes. As a result, bronchiolitis hospitalizations may be considered an upper bound of RSV hospitalizations. These disparities in RSV epidemiology by insurance payer highlight the need for monitoring disenfranchised populations and ensuring access to preventive measures for all infants.