Cost-effectiveness of recombinant influenza vaccine compared with standard-dose influenza vaccine among adults 50 years of age and older in Hong Kong

Older adults face a disproportionately high risk of severe influenza, yet the standard inactivated influenza vaccine (IIV) offers suboptimal protection in this population. This study evaluates the cost-effectiveness of replacing IIV with the recombinant influenza vaccine (RIV) for adults aged ≥50, ≥65, and ≥80 years in Hong Kong. We used a decision tree model to compare RIV with IIV for adults aged ≥50, ≥65, and ≥80 years in Hong Kong, from a societal perspective. Costs, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios (ICERs) were evaluated, and the impact of parameter uncertainty on the results was assessed via deterministic and probabilistic sensitivity analyses. We found that for adults ≥ 50 years, RIV increased total costs by USD 5.1 (HKD 39.8) per person and gained 0.00012 QALYs (ICER: USD 40,659 [HKD 317,140] per QALY) compared with IIV. Among adults ≥65 years, RIV cost USD 6.0 (HKD 46.8) more and gained 0.00021 QALYs (ICER: USD 29,077 [HKD 226,801] per QALY). For adults ≥80 years, RIV cost USD 3.2 (HKD 25.0) more and gained 0.00015 QALYs (ICER: USD 21,092 [HKD 164,518] per QALY). ICERs were less than willingness-to-pay thresholds of one to three times Hong Kong's gross domestic product per capita. In conclusion, RIV is cost-effective compared with IIV for adults ≥50, ≥65, and ≥80 years in Hong Kong, with the lowest ICER observed in individuals ≥80 years.