Modeling the impact of vaccine campaigns on the epidemic transmission dynamics of chikungunya virus outbreaks.

A licensed chikungunya vaccine now exists; however, it remains unclear whether it could be deployed during outbreaks to reduce the health burden. We used an epidemic in Paraguay as a case study. We conducted a seroprevalence study and used models to reconstruct epidemic transmission dynamics, providing a framework to assess the theoretical impact of a vaccine had it been available. We estimated that 33.0% (95% confidence interval (CI) 30.1-36.0%) of the population became infected during the outbreak. Of these individuals, 6.3% (95% CI 5.8-6.9%) were detected by the surveillance system, with a mean infection fatality ratio of 0.013% (95% CI 0.012-0.014%). A disease-blocking vaccine with 75% efficacy deployed in 40% of individuals aged ≥12 years over a 3-month period would have prevented 34,200 (95% CI 30,900-38,000) cases, representing 23% of all cases, and 73 (95% CI 66-81) deaths. If the vaccine also leads to infection blocking, 88% of cases would have been averted. These findings suggest that the vaccine is an important new tool to control outbreaks.