Fig. 4. Effect of digital contact tracing and household isolation by age and setting.

(A) Repartition among the different settings of the contacts detected by contact tracing (57% app adoption). (B) TRR by setting obtained with household isolation (HHI). The relative reduction in transmission is here defined as $\mathit{TRR}(s)=\frac{I_{\text{ref}}^{\mathrm{s}}-I^{\mathrm{s}}}{I_{\text{ref}}^{\mathrm{s}}}$, where I^s is the total number of clinical and subclinical cases infected in setting s, in the given intervention scenario considered (here household isolation) and $I_{\text{ref}}^{\mathrm{s}}$ is the same quantity in the reference scenario (here the scenario with no intervention). (C) TRR obtained with digital contact tracing with respect to household isolation only, for three values of app adoption. (D) Repartition among the different age groups of the index cases and of the detected contacts, in a scenario with household isolation only, and with the inclusion of digital contact tracing (57% app adoption). The repartition of index cases is very similar in the two scenarios; thus, only the one with household isolation is shown for the sake of clarity. (E) TRR by age group of the infected as obtained with household isolation only. (F) TRR of digital contact tracing with respect to household isolation only. We assume R = 2.6, immunity 10%, and probability of detection 50%.