Fig. 4: South African RBD variant has decreased neutralization compared to wild-type in vaccinated and infected samples.

Neutralization for the South African variant (SA) displayed as virus neutralizing titers (VNT₅₀) was measured in a virus neutralization assay compared to a wild-type variant (wt) (a) with sera from vaccinated (pre second vaccination (light blue, n = 9), post second vaccination (dark blue, n = 7)), infected (red, n = 6), and negative (pre-pandemic) (gray, n = 2) individuals. To confirm the reduction in neutralization seen, an ACE2 competition assay was developed and used to measure neutralization capacity for wild-type RBD (wt) and the South African RBD mutant (SA) (b) on sera from vaccinated (pre second vaccination (light blue, n = 25), post second vaccination (dark blue, n = 20)), infected (red, n = 35) and negative (pre-pandemic, gray, n = 20) individuals. 0 indicates that no neutralization is present while 1 indicates maximum neutralization. A linear regression (y = −0.044 + 0.408x) for all samples is shown in gray with the R² included. When examining vaccinated samples only, wild-type neutralization (c) is significantly increased following the second vaccine dose. For South African neutralization (d), while it is increased following the second dose, there is a significant reduction when compared to wild-type. Lines in (a), (c), and (d) indicate paired samples from the same donor. Source data are provided as a Source Data file.