Estimates of the severity of COVID-19 disease

Robert Verity; Lucy C Okell; Ilaria Dorigatti; Peter Winskill; Charles Whittaker; Natsuko Imai; Gina Cuomo-Dannenburg; Hayley Thompson; Patrick Walker; Han Fu; Amy Dighe; Jamie Griffin; Anne Cori; Marc Baguelin; Sangeeta Bhatia; Adhiratha Boonyasiri; Zulma M Cucunuba; Rich Fitzjohn; Katy A M Gaythorpe; Will Green; Arran Hamlet; Wes Hinsley; Daniel Laydon; Gemma Nedjati-Gilani; Steven Riley; Sabine van-Elsand; Erik Volz; Haowei Wang; Yuanrong Wang; Xiayoue Xi; Christl Donnelly; Azra Ghani; Neil Ferguson

The copyright holder for this preprint . https://doi.org/10.1101/2020.03.09.20033357 doi: medRxiv preprint Table 1 shows estimates of the CFR obtained from aggregate data on cases and deaths in mainland China. A large proportion of the cases, including all of those early in the epidemic, were reported from Wuhan where the local health system was quickly overwhelmed. Furthermore, the case definition outside Wuhan required a travel-link to Wuhan. Figure 3A shows a difference in the resulting agedistribution of cases reported from these two areas. Reported cases in Wuhan are more frequent in older age-groups, perhaps reflecting higher severity (and hence prioritisation for hospitalisation in Wuhan) whilst cases outside Wuhan may also represent a bias in terms of the relationship between age and travel. Adjusting for differences in underlying demography and assuming no overall difference in the attack rate by age, we estimate a high level of under-ascertainment of cases in younger agegroups in both Wuhan and outside Wuhan (Figure 3 C-D). Furthermore, we estimate a higher level of under-ascertainment overall in Wuhan compared to outside Wuhan ( Figure 3C ). Accounting for this under-ascertainment, we estimate the highest CFR in the 80+ age-group of 13.4% (11.2-15.9%) ( Figure 3B , Table 1 ). Our estimates of CFR decline rapidly with decreasing age, with very low rates in young adults and children.