OBJECTIVES: Despite routine vaccination, pertussis remains an important public health problem with an increase in annual incidences worldwide in recent years. Since infants too young to be protected by vaccination remain at risk of severe pertussis-related morbidity, New Zealand Authorities recommended and funded maternal immunisation against pertussis in 2013. In this study, we evaluated the cost-effectiveness of adding a maternal immunisation program to routine vaccination prior to 2013 in New Zealand. METHODS: A decision-tree model was adapted from the literature. A cohort of infants below 1 year of age (corresponding to the birth cohort in New Zealand) and a cohort with their mothers are followed. Data on pertussis morbidity and costs were gathered for infants and their mothers. Health benefits (in quality-adjusted life-years [QALYs]) and costs were estimated. Incremental cost-effectiveness ratio was calculated from a payer's perspective. The robustness of results was determined through scenario analysis (years of low, high and average incidence) and sensitivity analysis. RESULTS: In the base-case analysis (average incidence 2009-2012, 20% coverage, 1:100 underreporting), maternal immunisation was found to reduce the incidence of pertussis among infants (62 infant cases prevented) and was estimated to have a cost-effectiveness ratio of NZD 527.17/QALY from a payer's perspective. During a high incidence year maternal immunisation was dominant. During a low incidence year maternal immunisation was estimated to have a cost-effectiveness ratio below NZD 32,577.42/QALY. In the scenario analysis, the cost-effectiveness of maternal immunisation remained below that ratio and even dominant in most cases. DISCLAIMER: This is a cost-effectiveness study only. There is currently no pertussis immunisation indication/label for pregnancy in New Zealand and any immunisation should be consistent with local product labelling.