The most cost-effective means of decreasing transmission of Zika virus is the vaccination of young adults and women of childbearing age, according to a study published in the Journal of Infectious Diseases. The more people who are vaccinated, the fewer cases will result; however, focusing on these groups is the most economic means of reducing Zika virus cases.
This study included 2 models: one for Zika clinical and economic outcomes, and another for transmission. These models used data on the number of Zika cases in Brazil, Honduras, and Puerto Rico and evaluated them into health outcomes and their respective healthcare and societal costs. A baseline scenario included a simulation of an outbreak of Zika with a completely unvaccinated population.
Researchers then used simulations to introduce different outbreaks of the virus to target populations stratified by age, including all ages, young adults (aged 15 to 20 years), children of school (aged 5 to 14 years), and women of childbearing age (aged 15 to 49 years). A Monte Carlo simulation varied individual factors in the model to provide a set of 1000 sample trials, with vaccination cost ($5 to $50), target population coverage (25% to 75%), efficacy (25% to 75%), rate of Zika attack at 5 years (2% to 50%), and length of time between vaccination and outbreak (1 to 5 years).
Compared with no vaccination, cost-effectiveness was achieved with a $5 vaccination for Honduran women of childbearing age with a 2% rate of attack (incremental cost-effectiveness ratio: $790 to $5270 per disability-adjusted life-year prevented). In Brazil, an outbreak with at least a 20% attack rate and a 25% vaccine efficacy corresponded with a ≤$50 vaccination (incremental cost-effectiveness ratio: $255 to $390 per disability-adjusted life-year prevented). Vaccination was dominant from both viewpoints in Puerto Rico. For school-age children, the cost was $5002 per disability-adjusted life-year prevented in Honduras. In Brazil, there was a savings of $819 to $1609 per prevented case, and in Puerto Rico the figure was $3823 to $4360. Young adults had an incremental cost-effectiveness ratio of $731 to $4017 per disability-adjusted life-year prevented in Honduras, a savings of $953 to $1703 per prevented case in Brazil, and $3857 to $4372 in Puerto Rico. A blanket vaccination for all ages was more effective, but more expensive, which resulted in poorer individual cost-savings. Higher attack rates correlated with better outcomes and cost-savings for vaccinations.
Limitations to this study included the inherent simplification of modeling, an assumption of homogeneous mixing among humans and vectors, a potential underestimation of the vaccine’s benefit, and continuously emerging new research regarding Zika.
The study researchers concluded that “[while] vaccinating everyone will naturally avert the most cases, specifically vaccinating women of childbearing age or young adults garnered the highest economic value, often resulting in cost savings, even when considering transmission.”
Bartsch SM, Asti L, Cox SN, et al. What is the value of different Zika vaccination strategies to prevent and mitigate Zika outbreaks? [published online December 13, 2018]. J Infect Dis. doi: 10.1093/infdis/jiy688