Date Published: April 29, 2019
Publisher: Public Library of Science
Author(s): Samuel K. Peasah, Martin I. Meltzer, Michelle Vu, Danielle L. Moulia, Carolyn B. Bridges, Chiara Lazzeri.
Although influenza vaccination has been shown to reduce the incidence of major adverse cardiac events (MACE) among those with existing cardiovascular disease (CVD), in the 2015–16 season, coverage for persons with heart disease was only 48% in the US.
We built a Monte Carlo (probabilistic) spreadsheet-based decision tree in 2018 to estimate the cost-effectiveness of increased influenza vaccination to prevent MACE readmissions. We based our model on current US influenza vaccination coverage of the estimated 493,750 US acute coronary syndrome (ACS) patients from the healthcare payer perspective. We excluded outpatient costs and time lost from work and included only hospitalization and vaccination costs. We also estimated the incremental cost/MACE case averted and incremental cost/QALY gained (ICER) if 75% hospitalized ACS patients were vaccinated by discharge and estimated the impact of increasing vaccination coverage incrementally by 5% up to 95% in a sensitivity analysis, among hospitalized adults aged ≥ 65 years and 18–64 years, and varying vaccine effectiveness from 30–40%.
At 75% vaccination coverage by discharge, vaccination was cost-saving from the healthcare payer perspective in adults ≥ 65 years and the ICER was $12,680/QALY (95% CI: 6,273–20,264) in adults 18–64 years and $2,400 (95% CI: -1,992–7,398) in all adults 18 + years. These resulted in ~ 500 (95% CI: 439–625) additional averted MACEs/year for all adult patients aged ≥18 years and added ~700 (95% CI: 578–825) QALYs. In the sensitivity analysis, vaccination becomes cost-saving in adults 18+years after about 80% vaccination rate. To achieve 75% vaccination rate in all adults aged ≥ 18 years will require an additional cost of $3 million. The effectiveness of the vaccine, cost of vaccination, and vaccination coverage rate had the most impact on the results.
Increasing vaccination rate among hospitalized ACS patients has a favorable cost-effectiveness profile and becomes cost-saving when at least 80% are vaccinated.
Annual influenza vaccination has long been recommended for adults with certain medical conditions including cardiovascular disease (CVD), diabetes, and chronic lung disease, because of the increased risk of influenza-related complications, including hospitalization and death [1,2]. Influenza illness results in substantial economic impact, including costs related to outpatient and inpatient medical care, medications, lost productivity, decreased quality-of-life, and loss of life . The association between influenza infection and acute myocardial infarction (AMI) or other major cardiac events has been established in the literature and CVD is the most commonly identified chronic medical condition among adults hospitalized with influenza [4–7]. A recent study found a significant association between influenza infection and acute myocardial infarction .
We developed a spreadsheet-based Monte Carlo probabilistic model (@Risk version 7 Palisade Corporations)  in 2018 to estimate the cost-effectiveness of increased influenza vaccination in a single year’s cohort (Fig 2) of ACS patients against readmitted MACE (S1 Table). The intended population is an estimated 625,000 ACS non-institutionalized (includes non-federal, short-term general, and other hospitals but excludes long-term care, rehabilitation and other institutions such as prisons) patient-discharges among persons, aged ≥18 years, in the United States [18,20,21]. Approximately 13% of these patients are classified as MACE after the ACS hospitalization . Our model evaluates the protective benefit of influenza vaccination against MACE readmissions at the current vaccination rate among patients who report having cardiovascular disease and at 75% vaccination of admitted ACS patients. The health outcomes of interest are the number of MACE readmissions averted and the quality-adjusted life years (QALYs) gained. The model outputs are the incremental cost-effectiveness (ICER) of influenza vaccination against readmitted MACE at the current vaccination rate compared to a 75% vaccination rate pre-discharge in the natural units (cost/averted MACE) and in utilities (cost/QALY). Attaining 100% vaccination rate is ideal but unrealistic, vaccine effectiveness varies yearly, and increasing vaccination rates will increase cost of vaccination, therefore, we additionally conducted sensitivity analysis among these uncertainties for vaccination rates up to 95%.
In the base case analysis (current vaccination rate vs. 75% vaccination rate), an additional ~500 (95% CI: 578–825) MACEs were averted at vaccine effectiveness of 36% against MACE and vaccine coverage of 63.4% for persons aged ≥ 65 years and 48% for persons aged 18–64 year. Similarly, the number of QALYs added will be ~600 (95% CI: 578–825). The additional influenza vaccination cost was $3 million (Table 2).
We estimated increasing vaccination from the current rate to 75% of ACS hospitalized patients against MACE to be cost-saving for adults aged ≥ 65 years and favorable economically for adults aged 18–64 years. In a sensitivity analysis, the impact of increasing vaccination rate up to 95% was cost-saving for all adults after 80%.
Adding influenza vaccination prior to discharge for patients admitted for ACS could substantially reduce subsequent re-hospitalization due to MACE. Achieving a vaccination rate of at least 80% could be cost-saving. All medical providers of patients with cardiovascular disease, including pharmacists, have a role in assessing patients’ vaccination status at each clinical encounter, including hospital discharge, providing a clear recommendation for influenza vaccination, and offering influenza vaccination and other vaccines as indicated. Medical primary care providers,  specialty providers and other vaccine providers, including pharmacists could prevent MACEs during the influenza season by stocking influenza vaccines and recommending influenza vaccination for all adult patients with CVD each year.