Expected Impact of Universal Immunization With Nirsevimab Against RSV-Related Outcomes and Costs Among All US Infants in Their First RSV Season: A Static Model

Abstract

Background Respiratory syncytial virus (RSV) is associated with substantial morbidity in the United States, especially among infants. Nirsevimab, an investigational long-acting monoclonal antibody, was evaluated as an immunoprophylactic strategy for infants in their first RSV season and for its potential impact on RSV-associated, medically attended lower respiratory tract illness (RSV-MALRTI) and associated costs. Methods A static decision-analytic model of the US birth cohort during its first RSV season was developed to estimate nirsevimab’s impact on RSV-related health events and costs; model inputs included US-specific costs and epidemiological data. Modelled RSV-related outcomes included primary care and emergency room visits, hospitalizations including intensive care unit admission and mechanical ventilations, and RSV-related mortality. Results Under current standard of care, RSV caused 529 915 RSV-MALRTIs and 47 281 hospitalizations annually, representing $1.2 billion (2021 US dollars [USD]) in costs. Universal immunization of all infants with nirsevimab is expected to reduce 290 174 RSV-MALRTI, 24 986 hospitalizations, and expenditures of $612 million 2021 USD. Conclusions An all-infant immunization strategy with nirsevimab could substantially reduce the health and economic burden for US infants during their first RSV season. While this reduction is driven by term infants, all infants, including palivizumab-eligible and preterm infants, would benefit from this strategy.

All Infants Are at Risk of Developing Medically Attended Respiratory Syncytial Virus Lower Respiratory Tract Infection and Deserve Protection

“…Kieffer et al [ 38 ] use a static decision analysis model to estimate that, without immunization, 1 in 7 infants have RSV MA-LRTI each year; that is, 47 281 hospitalizations (IP), 129 070 ED visits, and 353 563 OP visits, for a total of 529 915 encounters at an estimated cost of $124 billion annually. The authors go on to show that although IP visits accounted for 9% of encounters (24% ED visits; 67% OP visits), these encounters represented 91% of the annual RSV MA-LRTI economic burden, with mechanical ventilation (24%) and intensive care unit admissions (46%) composing 70% of those IP costs.…”

“…By contrast, palivizumab-eligible infants made up 6% of IP visits and 1% of ED and OP visits. Kieffer et al also show that 69% of all RSV MA-LRTI and 47% of IP RSV MA-LRTI occurred among infants born before the start of the season [ 38 ].…”

“…As expected, the vast majority of these averted medical encounters and costs occur among term infants because term infants make up >90% of all encounters. Importantly, infant deaths both in and outside the health system would also be reduced [ 38 ]. These results further support the importance of preventing RSV MA-LRTI among all infants.…”

The Burden of Respiratory Syncytial Virus Lower Respiratory Tract Disease in Infants in the United States: A Synthesis

“…A separate analysis using a static decision-analytic model that arrived at a considerably higher economic cost of RSV $1.2 billion showed that RSV hospitalization—despite contributing only 9% of the annual 529 915 healthcare case burden of RSV LRTI—resulted in 92% of the costs (27% hospitalization, 44% ICU admission, and 21% mechanical ventilation). In contrast, primary care and ED visits, although contributing to 91% of the healthcare burden, only accounted for 8% of the costs [ 34 ]. Because infant Medicaid recipients shoulder a major burden of RSV disease [ 19 ] and the associated costs [ 33 ], it is imperative that effective prevention measures also be offered to these infants [ 35 ].…”

The efficacy and safety of nirsevimab for the prevention of RSV infection among infants: A systematic review and meta-analysis

“…Indeed, the use of nirsevimab to prevent RSV infections and hospitalization shows its promising potential but studies on its cost-effectiveness are lacking. In a study by Kieffer and colleagues in 2022, it was estimated using a static model that universal immunization of all infants with nirsevimab is expected to reduce 290,174 RSV-MALRTI, 24,986 hospitalizations, and expenditures of $612 million USD ( 16 ). We therefore recommend that further studies be done to look into the applicability and cost-effectiveness of nirsevimab.…”