Cost-effectiveness analysis of pertussis vaccination during pregnancy in Japan.

Background: Both re-emergence of pertussis outbreak among adolescents/adults and recent approval of the extended use of DTaP vaccine for boosting adolescents/adults against pertussis in Japan, have raised the possibility of using aP-containing vaccine in pregnant women to protect neonates and unvaccinated infants. There is a need, therefore, to evaluate the value for money of such possibility.

Methods: We evaluated the cost-effectiveness of conducting antepartum maternal vaccination (AMV) strategy in Japan. Considering the duration of vaccine effectiveness for infant (single year) and for mother (multiple years), the decision tree model and Markov model was adapted for infant and mother, respectively. Incremental cost-effectiveness ratio (ICER) compared with current no AMV strategy from societal perspective were calculated. The transition probabilities, utility weights to estimate quality-adjusted life year (QALY), and disease treatment costs were either calculated or extracted from literature. Costs per vaccination was assumed at ¥6000/US$54.5. Markov model for mothers with one-year cycle runs up to year four after vaccination, based on the waning of vaccine effectiveness. Infant who survived from pertussis was assumed to live until to his/her life expectancy.

Results: AMV strategy reduces disease treatment costs, while the reduction cannot offset the vaccination cost. Incremental QALYs were at 0.0002802, among them 79.5% were from infants, and others from mothers. ICER was ¥9,149,317/US$83,176 per QALY gained. One-way sensitivity analyses identified that the incidence rate and costs per shot were the two main key variables to impact the ICER.

Conclusion: We found that vaccinating pregnant women with aP-containing vaccine to prevent neonatal and unvaccinated infants from pertussis-associated disease in Japan can be cost-effective from societal perspective, under the WHO-suggested "cost-effective" criteria (1 to 3 times of GDP). Pertussis is expected be designated as a notifiable disease in 2018, re-analysis should be conducted when straightforward incidence data is available.