Neutralization efficiency of convalescent sera against D614G, B.1.1.7 and B.1.617 pseudotyped viruses. (A) Neutralizing activity of convalescent plasma (n = 20) to D614G, B.1.1.7 and B.1.617 variants. Pseudotypes were incubated with different serum dilutions for 60 min at 37 °C, and then were added to the 293T-ACE2 cells. Upon 72 h, cells were lysed with passive lysis buffer and the activity of firefly luciferase was analyzed. The half-maximal neutralizing titer (ID50) was quantitatively analyzed using Graphpad 8.0 and the threshold of ID50 was 1:40. (B) Changes in convalescent sera ID50 against D614G, B.1.1.7 and B.1.617 and the GMT values.