Cost-Effectiveness and Impact of a Targeted Age- and Incidence-based West Nile Virus Vaccine Strategy

Background West Nile virus (WNV) is the leading cause of arboviral disease in the United States and is associated with significant morbidity and mortality. A previous analysis found that a vaccination program targeting persons aged >= 60 years was more cost-effective than universal vaccination, but costs remained high. Methods We used a mathematical Markov model to evaluate cost-effectiveness of an age- and incidence-based WNV vaccination program. We grouped states and large counties (>= 100 000 persons aged >= 60 years) by median annual WNV incidence rates from 2004 to 2017 for persons aged >= 60 years. We defined WNV incidence thresholds, in increments of 0.5 cases per 100 000 persons >= 60 years. We calculated potential cost per WNV vaccine-prevented case and per quality adjusted life-years (QALYs) saved. Results Vaccinating persons aged >= 60 years in states with an annual incidence of WNV neuroinvasive disease of >= 0.5 per 100 000 resulted in approximately half the cost per health outcome averted compared to vaccinating persons aged >= 60 years in the contiguous United States. This approach could potentially prevent 37% of all neuroinvasive disease cases and 63% of WNV-related deaths nationally. Employing such a threshold at a county level further improved cost-effectiveness ratios while preventing 19% and 30% of WNV-related neuroinvasive disease cases and deaths, respectively. Conclusions An age- and incidence-based WNV vaccination program could be a more cost-effective strategy than an age-based program while still having a substantial impact on lowering WNV-related morbidity and mortality. A West Nile virus (WNV) vaccination program targeting age groups and locations with elevated neuroinvasive disease incidence is more cost-effective than a national or age-based strategy alone and still would have a substantial impact on lowering WNV-related morbidity and mortality.