SARS-CoV-2 binding antibody responses
beta RBD
VIRUS
ELISA-based antibody titre analysis indicated that best responses for anti-RBD antibody were achieved for the 45 μg dose of protein vaccine with day 29 post-vaccination GM titre (GMT) of antibody against ancestral 10,390 (3.5-fold GMT rise, GMFR), beta of 12,730 (GMFR 4.0) and omicron BA.5 33,530 (GMFR 5.1) (Antibody responses. Binding antibody (ELISA, row A); live virus microneutralisation (row B); sVNT multiplex using Method A (see Suppl. Materials) (row C); sVNT using Method B (see ELISA titres, individual plots d1/d29. WT = ancestral strain. Bars are geometric means and 95% confidence intervals.ELISA titres, d1/d29 by prior COVID-19. (WT = ancestral strain).In terms of GMFR booster responses, there appeared to be a positive dose–response relationship for the Protein-RBD vaccine. Given that the baseline for the intermediate protein dose was the higher than the boosted response in the low dose group, it was difficult to determine whether the intermediate dose of protein vaccine provided a stronger boost than the lower dose because this will have reduced GMFR readings. A relationship was less clear for the mRNA-RBD vaccine in terms of GMFRs, where lower doses were quite immunogenic (BA.5 binding antibody titres were higher than those against ancestral and beta strains for both vaccines (33,530 for 45 μg Protein-RBD and 32,359 for 50 μg mRNA-RBD), with GMFRs of 5.1 and 2.4 for higher dose protein and mRNA vaccines respectively (During the course of our trial, licensed mRNA vaccines were updated to a bivalent format including an omicron strain (BA.1). This provided the opportunity to determine if our beta variant protein and mRNA vaccines induced similar antibody responses to an omicron bivalent vaccine. While these samples were tested in a separate ELISA run, and notwithstanding differences in baseline antibody GMTs, the results showed GMFR of 4.0, 3.1 and 5.2 against ancestral RBD, beta RBD and omicron BA.5 RBD which were comparable to the GMFRs from 45 μg Protein-RBD and 10 μg mRNA-RBD vaccines (