Disclosures: The authors report no relevant financial disclosures.
June 24, 2021
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Targeting specific people with West Nile vaccine more cost effective than national plan

Disclosures: The authors report no relevant financial disclosures.
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A West Nile vaccine plan that targets older people in areas of the United States with a high incidence of the virus would be a more cost-effective strategy than an age-based strategy alone, or a national plan, researchers said.

West Nile virus is the leading cause of mosquito-borne disease in the U.S., with more than 51,000 cases reported between 1999 and 2019, according to the CDC.

Culex mosquito
West Nile virus is primarily spread by Culex species mosquitoes.
Source
: CDC/James Gathany.

“This is particularly true for older adults, as the risk of neuroinvasive disease and death increases with age,” Carolyn Gould, MD, MSCR, a medical epidemiologist in the CDC’s Arboviral Disease Branch, told Healio. “Unfortunately, there are no proven treatments, and although several candidate vaccines are under development, none are approved for use in people yet.”

According to Gould, in previous analyses, a national vaccination strategy or age-based strategy for West Nile virus was not found to be cost-effective, although a vaccination program targeting persons aged 60 years or older was more cost-effective than universal vaccination.

Carolyn Gould

“Therefore, we evaluated cost-effectiveness and impact of a more targeted approach, vaccinating persons aged 60 years or older in states and counties with consistently elevated disease incidence, with the goal of guiding future vaccine development and implementation,” she said.

Gould and colleagues used modeling to evaluate cost-effectiveness of an age- and incidence-based West Nile virus vaccination program. According to the study, the researchers grouped states and large counties by median annual incidence rates from 2004 to 2017 for persons aged 60 years or older. They then calculated potential cost per vaccine-prevented case and per quality adjusted life-years (QALYs) saved.

Overall, the study showed that vaccinating people aged 60 years or older in states with an annual incidence of West Nile virus neuroinvasive disease of more than 0.5 per 100,000 people aged 60 or older resulted in approximately half the cost per health outcome averted compared with vaccinating persons aged 60 and older in all the contiguous U.S.

According to the study, this approach could potentially prevent 37% of all neuroinvasive disease cases and 63% of West Nile virus-related deaths nationally. Researchers also determined that retaining this threshold at a county-level improved cost-effectiveness ratios while preventing 19% of West Nile-related neuroinvasive disease cases and 30% of deaths.

“An age- and incidence-based West Nile virus vaccination program targeting older populations in areas with consistently high West Nile virus disease burden is more cost-effective than an age-specific or complete national program,” Gould said. “If a West Nile virus vaccine were to become available, states with high annual incidence of West Nile virus neuroinvasive disease could consider implementing a vaccination strategy targeting this population at a state or county level to substantially lower disease burden.”