Figure 2.

(A) Pooled overall household secondary attack rates. Studies are ordered by the number of index cases reported in the study. Studies of large household contact tracing investigations were included regardless of whether the number of index cases was reported in the study. (B) Stratified by duration of household exposure to symptomatic index case. Studies are ordered by the number of index cases reported in the study because this information was not given by exposure duration. Study-level point estimates and binomial confidence intervals are shown along with the pooled beta-binomial summary across studies. Exposure duration to the index case before isolation or hospitalization categories (≤5 days and >5 days) were selected to maximize usage of data.