Background: Recent surveillance indicates a resurgence of pertussis in the US. In 2012, over 48,000 pertussis cases were reported to the CDC, more than any year since 1955, with over half of all cases occurring in people aged greater than or equal to 11 years. 1 Individuals with chronic respiratory conditions such as asthma or chronic obstructive pulmonary disease (COPD) may be at higher risk for infection2, although the relationship between chronic respiratory diseases and the burden of pertussis remains uncharacterized. The present study examined the economic burden of pertussis among US adolescents and adults with asthma or COPD by comparing costs of diagnosed pertussis in patients with preexisting asthma or COPD to matched cohorts of patients without these conditions.
Methods: Retrospective analysis of administrative claims from the MarketScan Commercial Claims and Encounters and Medicare Supplemental (1/2006-6/2014) and Medicaid Multi-State (1/2007-12/2013) databases. These databases contain information on inpatient, outpatient, and pharmacy claims. All patients were required to have an ICD-9-CM diagnosis of pertussis. The index date was defined as the initial pertussis diagnosis date minus 15 days to allow for inclusion of care related to the pertussis diagnosis work-up. Patients were also required to have greater than or equal to 6 months of continuous enrollment before and after the index date and be aged greater than or equal to 11 years. Preexisting asthma and COPD were identified based on ICD-9-CM diagnosis and prescriptions before the index date. Patients with preexisting asthma or COPD were matched 1:1 to patients without these conditions. All-cause and pertussis-related costs during the 3-month pre- and post-index periods were calculated; the differences from pre- to post-index date (“incremental” costs) were reported for cases and controls. The incremental difference was the difference in incremental costs between cases and controls. Multivariate regressions were used to estimate adjusted incremental costs.
Results: A total of 1,041 patients with asthma and 343 patients with COPD were matched to an equal number of controls without these conditions. The mean (SD) age of the asthma and COPD cohorts was 32.1 (19.5) and 53.2 (18.4) years, with females comprising 63.6% and 63.0%, respectively. The highest proportion of pertussis diagnoses occurred in 2012. For patients with asthma, adjusted all-cause incremental costs increased by $2,189 in the 3 months post-index compared to $889 for controls (incremental difference=$1,301; p less than 0.01); adjusted pertussis-related costs averaged $572 for cases versus $332 for controls (difference=$241; p less than 0.01). Similarly, patients with COPD accrued $5,166 more in adjusted all-cause incremental costs in the 3 months post-index compared to $993 for controls (incremental difference=$4,173; p less than 0.01); adjusted pertussis-related costs averaged $1,130 for cases versus $695 for controls (difference=$435; p less than 0.01).
Conclusions: This analysis found substantial increases in adjusted incremental costs (both overall and pertussis-related) during the 3 months post-pertussis for patients with either preexisting asthma or COPD compared to controls. These results highlight an increased economic burden of pertussis in people with asthma or COPD, who may benefit from tetanus-diphtheria-acellular pertussis (Tdap) vaccination.
