OBJECTIVES: Conduct a cost-effectiveness analysis from the societal perspective of a one-time 10-year revaccination with tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine to prevent pertussis among individuals with pre-existing asthma in the US.
METHODS: A static, population-based model estimated the costs and health outcomes of Tdap revaccination at age 21 years (compared with no revaccination) for individuals aged 11-31 years with pre-existing asthma over a one-year time horizon, including quality-adjusted life-years (QALYs) gained due to deaths avoided. The model included only the incremental vaccine acquisition costs of Tdap vaccine over the recommended decennial tetanus and diphtheria vaccine. Model inputs, including vaccine effectiveness, utility decrements, and work days lost per pertussis case, were based on published literature. Pertussis incidence, hospitalization rate, and cost of treatment for patients with pre-existing asthma were based on a retrospective analysis of a large nationwide US healthcare claims database. To account for improved disease recognition, scenario analyses included a range of adjustment factors for underreporting of pertussis.
RESULTS: Vaccinating 11-year-olds followed by a 10-year Tdap revaccination resulted in an incremental cost of $21.05 million and 29.94 incremental QALYs gained compared to no revaccination. The QALYs gained resulted primarily from avoided outpatient cases (27.24 QALYs) and deaths (2.21 QALYs). The incremental cost-effectiveness ratio (ICER) of revaccination compared with no revaccination was $703,110 per QALY gained. When an underreporting factor of 10, 20, and 30 was applied to reported pertussis incidence, the ICERs decreased to $70,305, $35,152, and $23,435 per QALY gained, respectively.
CONCLUSIONS: Published economic evaluations have reported that revaccination with Tdap is not cost-effective at typical US willingness-to-pay thresholds, even with pertussis underreporting factors of up to 100; however, a 10-year revaccination with Tdap may be cost-effective among certain high-risk cohorts, including individuals with pre-existing asthma, that have higher risk of pertussis and more costly care.
