Modeling Exit Strategies from COVID-19 Lockdown with a Focus on Antibody Tests

Reinhard German; Anatoli Djanatliev; Lisa Maile; Peter Bazan; Holger Hackstein

The manifestation index of showing symptoms when infected is estimated to be within 69% and 86%. However, this might be larger, some estimations even assume a factor of unknown cases of up to 20. Severity is characterized as mild or moderate (without or with light pneumonia, 80%), severe (needs hospitalization without ICU, 14%), and critical (needs ICU 6%). The basic reproduction number R 0 is estimated to lie between 2.4 and 3.3, WHO estimates for China a range between 2 and 2.5 (without interventions). We assume a value of 3 to reflect the recorded cases in Germany. As in [10] we also allow for seasonal changes according to a sine function. For the incubation period (from infection to sickness) on the average 5 to 6 days can be assumed (range 1 -14) . For the latency period (from infection to being infectious) no results are given, we thus assume 3 days. The infection period can be assumed to start 2.5 days before onset of symptoms, the duration is unclear. Since the severity and duration of cases differ we calculate the infection period weighted by the number of cases (both symptomatic and asymptomatic), resulting in an average of 12.5 days including the prodromal period. Symptomatic period in mild or moderate cases is assumed to be 9 days according to [10] , we take the same time for asymptomatic cases. For the time from onset of symptoms to hospitalization an average of 4 is reported (with an interquartile range IQR of 2 -7) and from hospitalization to ICU on the average 1 day (IQR 0 -3). For the hospitalization time of severe cases and for the time in ICU we assume 14 and 10 days respectively as in [10] . Case fatality rates (CFRs) are counted in different ways and are uncertain, in [10] it is assumed that only ICU patients die with a percentage of 50%, in the RKI characterization also CFRs of 0.1% (mild) 8.1% (severe), 22% (critical) are suggested, we count moderate cases to be included into the mild ones. After the disease people have antibodies and are assumed to be immune. Even though the persistence is unclear, experience from other corona viruses suggest ca. 3 years, we assume here persistent immunity.