Intriguingly, the number of known pre-existing conditions was also highly correlated with IL-6 (r=0.25, p<0.01), sIL-6R (r=0.21, p<0.05) and sgp130 (r=0.29, p<0.01, Table 4) serum levels, underlining that pre-existing diseases are an important predictor of COVID-19 disease course. Here, IL6R is linked to COVID-19.