50 New Analysis on the Cost-effectiveness of Palivizumab (PVZ) for the Prevention of Severe Respiratory Syncytial Virus (RSV) Infection in Canadian Infants Born 29-31 and 32-35 weeks’ Gestational Age (wGA)
Authors: Fullarton John , Carbonell-Estrany Xavier , Keary Ian , Rodgers-Gray Barry , Tarride Jean-Eric , Paes Bosco 
Published: September 2023

Abstract

Background
PVZ remains the only licensed intervention to prevent severe RSV infection. The last formal cost-utility analysis (CUA) of its use in Canadian premature infants was published in 2010 (Smart J Med Econ 2010). Since then, the 3-variable International Risk Scoring tool (IRST) has been published (Blanken Pediatr Pulmonol 2018), which can guide prophylaxis for infants born 32-35 wGA at greatest risk of RSV hospitalization (RSVH).

Objectives
The objective of this study was to incorporate the IRST and non-hospitalized, medically-attended (emergency room/outpatient) RSV infections (MARI) into a CUA for the first time to provide an up-to-date economic evaluation of palivizumab versus no prophylaxis in Canadian 29-31 wGA and 32-35 wGA infants.

Design/Methods
Infants followed a semi-Markov process, having an RSVH, MARI, or being uninfected/non-medically attended. Hospitalized infants could be admitted to the intensive care unit (ICU; 17.9%) and ICU-admitted infants could die (0.43%). All surviving infants could experience respiratory morbidity up to 18 years, according to RSV infection and PVZ status. The RSVH rate in non-prophylaxed 29-31 wGA and moderate to high (MH) risk 32-35 wGA infants was 5.9% and 6.3%, respectively. PVZ reduced RSVH by 63.3% and 82.2% in 29-31 wGA and 32-35 wGA infants, respectively. PVZ costs (assuming 50 mg: CAN$752; 100 mg: $1,505) were calculated using Canadian birth statistics. The base case assumed all 29-31 wGA infants and MH-risk 32-35 wGA infants received PVZ, inclusion of indirect costs, no vial sharing, and a lifetime time horizon with 1.5% discounting. A cost per quality-adjusted life-year (QALY) of ≤$50,000 was considered cost-effective.

Results
PVZ prophylaxis resulted in a cost/QALY of $29,579 in 29-31 wGA infants and $27,951 in MH-risk 32-35 wGA infants versus no prophylaxis. In deterministic sensitivity analyses (±20% on main variables) the model was most sensitive to utility scores, PVZ cost, non-prophylaxed RSVH rate, and PVZ efficacy. Probabilistic sensitivity analyses (10,000 iterations) resulted in incremental costs of $30,857/QALY, with a 76.0% probability of cost-effectiveness at a $50,000 willingness-to-pay threshold for 29-31 wGA infants, and $28,167/QALY and 79.1% for MH-risk 32-35 wGA infants.

Conclusion
This new CUA, the first to incorporate the IRST and MARI, found that PVZ is highly cost-effective in Canadian 29-35 wGA infants (vs no prophylaxis) and has implications for prophylaxis policies in Canada.

Potential competing interests
Xavier Carbonell-Estrany and Bosco Paes have received research funding and/or compensation as advisor/lecturer from AbbVie and AstraZeneca. Jean-Eric Tarride has nothing to disclose. Barry Rodgers-Gray, Ian Keary and John Fullarton employers have received payment from AbbVie and AstraZeneca for work on various projects.