OBJECTIVES

To evaluate the cost-effectiveness of recommending a Tdap booster for adults at 18 years of age in Singapore

METHODS

A 20-year markov decision model was developed in TreeAgePro2018 to compare the proposed strategy of a Tdap booster at age of 18 to the current practice of no boosters for adults. The analysis was done separately for the adult population segment who had or had not received the last childhood booster recommended at the age of 10 as per the national children immunization schedule, Singapore. The study evaluated from both societal and healthcare perspective and reported the outcomes in terms of incremental cost-effectiveness ratio, number of cases avoided, additional healthcare costs and productivity losses saved. The undiagnosed burden of pertussis was accounted in the evaluation and sensitivity analysis was done to identify the significant variables.

RESULTS

The study found Tdap booster for adults to be not cost effective for both population segments without or with the childhood booster at the current reported annual clinical incidence of pertussis, being 2 per 100,000, an undiagnosed disease burden of 300 per 100,000 per year and a cost-effectiveness threshold of 50,000 US$/QALY. Clinical incidence and booster cost were found to be significant variables with threshold cost of US$8-14 or a clinical incidence of 48-67 per 100,000 adults independently driving booster strategy to cost-effectiveness. The booster strategy was also found to reduce the pertussis cases by 26-33%. Probabilistic sensitivity analysis found no booster strategy to be the preferred strategy for ≥85% of iterations at the threshold ICER of 50,000US$/QALY.

CONCLUSIONS

Tdap booster for pertussis is not a cost-effective strategy for adults but may become cost-effective at a cheaper booster cost or higher disease incidence. Separate evaluations should be done for elderly and pregnant women to identify the benefits in those population segments