(A) Neutrophil count, (B) lymphocyte count and (C) N:L ratio kinetic in non-severe (blue) and severe (red) forms of COVID-19. M-1: last monthly routine measure; D0: day of COVID-19 diagnosis. Data are expressed as mean ± SD. *P < 0.05, **P < 0.01, ns: non-significant (Mann–Whitney test).