APOE and COVID-19: APOE genotyping by Sanger sequencing and real-time PCR showed that 71.83% subjects are APOE ε3/ε3 (the ε3 carriers), and 28.17% subjects are APOE ε3/ε4 or ε4/ε4 (the ε4 carriers) in a Chinese cohort of 142 COVID-19 patients excluding APOE ε2 carriers (Fig. 4a and Supplementary Table S2).