Estimates of the Undetected Rate among the SARS-CoV-2 Infected using Testing Data from Iceland

James H Stock; Karl M Aspelund; Michael Droste; Christopher D Walker

The results are summarized in Table 2 . The primary estimate of the lower bound using the eligibility window method uses the infection rate among the asymptomatic from the deCODE tests and assumes that none of the NUHI-ineligible quarantined are infected; this yields an undetected rate of 88.7% (95% confidence interval 83.9% to 93.5%). The second line re-estimates the lower bound using the overall deCODE positive testing rate, which includes the mildly symptomatic; because the mildly symptomatic have a somewhat higher deCODE positive testing rate than the asymptomatic, the estimate of the population infection rate is somewhat larger and the undetected fraction is somewhat larger, 92.5%. As discussed, the NUHI testing eligibility guidelines were broadened after March 19, and using data postdating this broadening results in slightly lower estimates of the undetected rate, approximately 85%.