The Economic Implications of Influenza Vaccination for Adults with Asthma

Abstract

Influenza vaccination is recommended for adults with asthma. This study estimates the effect of influenza vaccination on utilization of medical services and expenditures for acute and chronic respiratory conditions (ACRC) among adults with asthma. The sample was adults aged ≥18 years self-reporting asthma in the 2003 through 2006 Medical Expenditure Panel Survey (MEPS), covering four complete influenza seasons. The dependent variables were indicators for any ACRC claims within service category and ACRC expenditures. The main independent variable was an indicator of influenza vaccination. To control for selection bias in the observational data, a nonlinear instrumental variables approach was used. The instruments were indicators for influenza in the first year of MEPS and vaccination in the year prior to MEPS. Data were analyzed in 2009. Adults with asthma vaccinated for influenza were 4.4 percentage points less likely to have an inpatient stay due to ACRC (95% CI = -10.8, -1.0). Influenza vaccination was associated with a $492 decrease (95% CI = -$1591, -$56) in annual ACRC nonprescription expenditures, a $224 increase (95% CI = $70, $360) in annual ACRC prescription expenditures, and a nonsignificant $216 decrease (95% CI = -$854, $248) in overall annual ACRC expenditures. Although there was no evidence that vaccination reduced overall ACRC expenditures, the study suggests that efforts to increase the percentage of adults with asthma who are vaccinated may bring substantial benefits in terms of reducing the prevalence and costs of hospitalization although raising prescription medication costs, possibly through improvement in compliance.