Anti–WT-RBD IgG titers were significantly increased after Delta breakthrough infection in individuals who received two doses of mRNA vaccine (Delta BT), compared to vaccinated individuals who did not experience infection (5 m-Vax2; P < 0.0001, Vax2 [Cho et al., 2021] vs. Delta; Fig. 1 b and Table S1). The gene discussed is VAX2; the disease is infection.