Cost-effectiveness analysis of universal adult immunization with tetanus-diphtheria-acellular pertussis vaccine (Tdap) versus current practice in Brazil

Background A pertussis outbreak occurred in Brazil from 2011 to 2014, despite high coverage of whole-cell pertussis containing vaccines in early childhood. Infants were the most affected. This study aimed to evaluate the cost-effectiveness of introducing universal adult vaccination with Tdap into the National Immunization Program in Brazil. Methods Economic evaluation using a dynamic model to compare two strategies: (1) universal vaccination with single dose of Tdap at 20 years of age and (2) current practice (only pregnant women pertussis vaccination). The health system perspective was adopted. Temporal horizon was 10 years. Discount rate of 5% was applied to costs and benefits. Vaccine effectiveness (VE) was obtained from a population-based observational study. Epidemiological, resource utilization and cost estimates were obtained from the Brazilian Health Information Systems. The primary outcome was cost per life year saved (LYS), based on life expectancy at birth in Brazil in 2015. Univariate and multivariate sensitivity analysis were performed. Results Adult vaccination with VE of 82.6% and coverage of 40%, at price of US$7.01 per dose, and assuming herd protection would avoid 167 infant deaths by pertussis, saving 12,325 years of life and costing a total of US$105495891.61, from the health system perspective. The universal immunization would result in ICER of US$8459.13. The results were highly sensitive to disease incidence. Conclusions The results suggest that universal adult vaccination with Tdap would not be a cost-effective intervention for preventing pertussis cases and deaths in infants in Brazil.