OBJECTIVES: Despite widespread childhood immunization, there is a resurgence of pertussis infections and resultant clinical sequelae as adults infect children who are too young to be fully vaccinated or whose immunity is waning. A reduced antigen dTpa booster pertussis vaccine (Boostrix) is now available. The goal of this effort was to evaluate its cost-effectiveness. METHODS: A literature-based model was developed to quantify the clinical and economic costs and benefits of vaccinating parents with Boostrix following the birth of their first child. The model projected and compared the number of adult infections avoided in two hypothetical cohorts (one with and one without vaccination) of one million parent couples over ten years. The model also quantified the number of pediatric infections avoided due to reduced infectivity of vaccinated parents. RESULTS: Immunization with Boostrix led to the following projected discounted benefits: avoidance of 1,178 pediatric and 44,264 adult pertussis infections, 1.3 pediatric encephalopathy cases, 0.4 pediatric chronic brain damage cases, and 1.4 pediatric deaths. Vaccination led to reductions in direct medical interventions, valued at $15.2 million, and prevented lost productivity, valued at $28.9 million, for a total savings of $44.1 million. Including the cost of vaccination of $20.0 million ($10 per adult), the net discounted savings of vaccination was estimated at $24.1 million. The largest cost savings were due to adult outpatient cases avoided (78%) and total (adult and pediatric) hospital stays avoided (13%). The program amounts to a net savings of $12.07 per vaccinee. In univariate sensitivity analyses in which each model input was varied by ±25 percent, the net savings per vaccinee ranged from $5.14 to $18.99. CONCLUSIONS: In this model, vaccinating young parents with Boostrix appears to be a cost-saving preventive measure. Driving this result is the large cost savings attributable to far fewer adult outpatient pertussis cases.