Cost-effectiveness of influenza vaccination of older adults in the ED setting

Abstract

Objectives: Adults older than 50 years are at greater risk for death and severe disability from influenza. Persons in this age group, however, are frequently not vaccinated, despite extensive efforts by physicians to provide this preventive measure in primary care settings. We performed this study to determine if influenza vaccination of older adults in the emergency department (ED) may be cost-effective.

Methods: Using a probabilistic decision model with quasi-Markov modeling of a typical influenza season, we calculated costs and health outcomes for a hypothetical cohort of patients using parameters from the literature. Three ED-based intervention strategies were compared: (1) no vaccination offered, (2) vaccination offered to patients older than 65 years (limited strategy), and (3) vaccination offered to all patients who are 50 years and older (inclusive strategy). Outcomes were measured as costs, lives saved, and incremental costs per life saved. We performed deterministic and probabilistic sensitivity analyses.

Results: Vaccination of patients 50 years of age and older results in an incremental cost of $34,610 per life saved when compared with the no-vaccination strategy. Limiting vaccination to only those older than 65 years results in an incremental cost of $13,084 per life saved. Results were sensitive to changes in vaccine cost but were insensitive to changes in other model parameters.

Conclusions: Vaccination of older adults against influenza in the ED setting is cost-effective, especially for those older than 65 years. Emergency departments may be an important setting for providing influenza vaccination to adults who may otherwise have remained unvaccinated.

Figure 1. Diagram of Markov states used in the model

Blue arrows represent transitions possible in all model strategies. In interventional strategies, patients seen in the ED have the additional option of being vaccinated in the ED, represented by the red arrow in the diagram. In the non-interventional arms, all patients seen in the ED move back to the unvaccinated state along the green transition.

Figure 2

Cost-effectiveness acceptability curves for the intervention strategies. Above a WTP of roughly $100 000 per life saved, vaccination for adults older than 65 years becomes the strategy most probable to be cost-effective.

Figure 3

Effects of changes in cost per life saved on the cost of influenza vaccination in ED setting. Below a cost of approximately 28.00, the intervention becomes cost saving for the older-than-65-years age group. Below $25, it becomes cost saving for all adults older than 50 years.

Figure 4. Effect of Changes in the Influenza Incidence Rate on Incremental cost-Effectiveness

Emergency department influenza vaccination becomes more cost-effective strategy as attack rate increases over the base incidence. ICERs are calculated between each intervention strategy and next most expensive competing strategy.