Defining high-value information for COVID-19 decision-making

Joshua A Salomon

We assume that the rate of transmission from asymptomatic individuals is systematically lower than the transmission probability from symptomatic individuals, but there are few empirical estimates for this reduction in transmission. We calibrated the relative infectiousness of asymptomatic individuals across a range of 25% to 66%. This range was derived from the values used by other researchers: Zhao et al. (2020) used 50% (which is similar to the estimate for influenza); Prem et al. (2020) used 25% (which they derived from Liu et al. (2020) ); and Ferguson et al. (2020) used 66%. Mizumoto et al. (2020) estimate that, among individuals on the Diamond Princess Cruise ship, 20.6% to 39.9% of infected individuals are asymptomatic, depending on the mean incubation period used by their model (they evaluated mean incubation periods between 5.5 and 9.5 days). Based on these results, we calibrate the proportion of asymptomatic infections for individuals 20 years and older across the range of 20% to 40%. This range is also supported by Nishiura et al. (2020) , which found that 30.8% (95% CI: 7.7, 53.8) of infected individuals among Japanese citizens evacuated from Wuhan, China were asymptomatic.