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

Per incidence proxy unit, the effect of the cross-immunizing strain was always less than the effect of the strain itself (Table S1), but the overall impact of cross-immunity could still be substantial if the cross-immunizing strain had a large outbreak (e.g. HCoV-OC43 in 2014-15 and 2016-17) . Seasonal forcing appears to drive the rise in transmissibility at the start of the season (late October through early December), while depletion of susceptibles plays a comparatively larger role in the decline in transmissibility towards the end of the season. The strain-season coefficients were fairly consistent across seasons for each strain and lacked a clear correlation with incidence in prior seasons, consistent with experimental results showing substantial waning of immunity within a year (14) .