Herd immunity on chip: recapitulating virus transmission in human society

Virus transmission is affected by population density, social distancing, and vaccination. This has been simulated only by mathematical models. Here, we report the first experimental model to mimic herd immunity to a human coronavirus using a microfluidic device filled with host cells. The device consists of 444 microchambers filled with susceptible (S 0 ), infected (I 0 ), and unsusceptible (U 0 ) cells at specific ratios. The transmission rate and reproduction numbers were directly proportional to S 0 and I 0 and inversely proportional to U 0 . Herd immunity was achieved when the proportion of U 0 was at 80% in a fixed number of uninfected (S 0 +U 0 ) cells. These results were consistent with those from a mathematical model. The device can be used for predicting virus transmission. One-Sentence Summary We present the first experimental model enabling the simulation of herd immunity in a microfluidic device filled with host cells to human coronavirus.