Projecting the transmission dynamics of SARS-CoV-2 through the post-pandemic period

Stephen M Kissler; Christine Tedijanto; Edward Goldstein; Yonatan H. Grad; Marc Lipsitch

We used data from the United States to model betacoronavirus transmission in temperate regions and to project the possible dynamics of SARS-CoV-2 infection through the year 2025. We first assessed the role of seasonal variation, duration of immunity, and cross immunity on the transmissibility of HCoV-OC43 and HCoV-HKU1 in the US. We used the weekly percentage of positive laboratory tests for HCoV-OC43 and HCoV-HKU1 (17) multiplied by the weekly population-weighted proportion of physician visits due to influenza-like illness (ILI) (18, 19) to approximate historical betacoronavirus incidence in the US to within a scaling constant. This proxy is proportional to incidence under a set of assumptions described in the Materials and Methods. To quantify variation in transmission strength over time, we estimated the weekly effective reproduction number, defined as the average number of secondary infections caused by a single infected individual (20, 21) . The effective reproduction numbers for each of the betacoronaviruses displayed a seasonal pattern, with annual peaks in the effective reproduction number slightly preceding those of the incidence curves (Fig S1) . For both HCoV-OC43 and HCoV-HKU1, the effective reproduction number typically reached its peak between October and November and its trough between February and April. Over the five seasons included in our data (2014-2019), the median effective reproduction number was 1.11 (IQR: 0.84-1.41) for HCoV-HKU1 and 1.00 (IQR: 0.84-1.41) for HCoV-OC43. Results were similar using various choices of incidence proxy and serial interval distributions (Fig S1, Fig S2) .