Tafenoquine following G6PD screening versus primaquine for the treatment of vivax malaria in Brazil: a cost-effectiveness analysis using a transmission model

ABSTRACT Background Malaria transmission modelling has demonstrated the potential impact of semi-quantitative glucose-6-phosphate dehydrogenase (G6PD) testing and treatment with single-dose tafenoquine for Plasmodium vivax radical cure. This modelling has focused on predicting the number of vivax cases averted, rather than its cost-effectiveness. Methods We explored the cost-effectiveness of using tafenoquine after G6PD screening as compared to usual practice (7-day low-dose primaquine (0.5 mg/kg/day) without G6PD screening) in Brazil using a 10-year time horizon with 5% discounting considering four scenarios: 1) tafenoquine for adults only assuming 66.7% primaquine treatment adherence, 2) tafenoquine for adults and children aged >2 years assuming 66.7% primaquine adherence, 3) tafenoquine for adults only assuming 90% primaquine adherence, 4) tafenoquine for adults only assuming 30% primaquine adherence. The incremental cost-effectiveness ratios (ICERs) were estimated by dividing the incremental costs by the disability-adjusted life-years (DALYs) averted. These were compared to a willingness to pay threshold of US$7,800 for Brazil, and one-way and probabilistic sensitivity analyses were performed. Results All four scenarios were cost-effective using this willingness to pay threshold with ICERs ranging from US$154–1836. One-way sensitivity analyses showed that the results were most sensitive to severity and mortality due to vivax malaria, the lifetime and number of semi-quantitative G6PD analysers needed, cost per malaria episode and per G6PD test strips, and life expectancy. All scenarios had a 100% likelihood of being cost-effective at the willingness to pay threshold. Conclusions Tafenoquine prescribed after a semi-quantitative G6PD testing is highly likely to be cost-effective in Brazil.