Modelling the Economic Impact of lnfluenza Vaccine Programs with the Cell-Based Quadrivalent Influenza Vaccine and Adjuvanted Trivalent Influenza Vaccine in Canada

Abstract

In Canada, approximately 12,000 people annually are hospitalized with influenza. While vaccination is the most effective method for reducing the burden of seasonal influenza, the propagation of vaccine virus strains in eggs can result in egg adaption, resulting in reduced antigenic similarity to circulating strains and thus lower vaccine effectiveness (VE). Cell-based propagation methods avoid these alterations and therefore may be more effective than egg-propagation vaccines. We evaluated three different scenarios: (1) egg-based quadrivalent influenza vaccine (QIVe) for individuals <65 years and adjuvanted trivalent influenza vaccine (aTIV) for ≥65 years; (2) QIVe (<65 years) and high-dose QIV (HD −; QIV; ≥65 years); and (3) cell-based derived QIV (QIVc; <65 years) and aTIV (≥65 years) compared with a baseline scenario of QIVe for all age groups. Modelling was performed using a dynamic age-structured SEIR model, which assessed each strain individually using data from the 2012−2019 seasons. Probabilistic sensitivity analysis assessed the robustness of the results with respect to variation in absolute VE, relative VE, number of egg-adapted seasons, and economic parameters. QIVe + aTIV was cost-saving compared with the baseline scenario (QIVe for all), and QIVe + HD − QIV was not cost-effective in the majority of simulations, reflecting the high acquisition cost of HD − QIV. Overall, while the incremental benefits may vary by influenza season, QIVc + aTIV resulted in the greatest reductions in cases, hospitalizations, and mortality, and was cost-effective (ICER < CAD 50,000) in all simulations.

Keywords: Canada; ICER; cell-based influenza vaccine; cost-effectiveness; influenza.

Figure 1

Outline of the epidemiological and economic model structures. S, E, I, and R represent susceptible, exposed, infectious, and recovered individuals, respectively, for the individual influenza strains. VS, VE, and VI represent susceptible, exposed and infectious individuals who received an influenza vaccine which was non-protective for the strain in question; VR represents individuals who were vaccinated and protected against influenza (either through infection following non-protective vaccination or through vaccination). In the economic model, infected individuals are categorized based on their healthcare usage. ER, emergency room; GP, general practitioner; ICU, intensive care unit.

Figure 2

(a) Number of cases, (b) number of hospitalizations, and (c) number of deaths prevented by each vaccine scenario, compared with the baseline scenario, for each of the rVE values evaluated.

Figure 3

Probabilistic sensitivity analysis of three scenarios compared with the baseline (QIVe for all age groups), assuming six egg-adapted seasons. Costs are presented as CAD. The yellow line indicates the willingness to pay the threshold (CAD 50,000).

Figure 4

Cost-effectiveness acceptability curves for each of the three scenarios, assuming six egg-adapted seasons. The threshold for cost-effectiveness was CAD 50,000.