Fig. 4

Antibody responses following adenovirus COVID-19 vaccination in previously infected adults. A Concentration of anti-Spike and anti-RBD IgG antibodies pre- and post-vaccination with a single dose of AstraZeneca COVID-19 vaccine. All antigens were from the original strain. B Representative plate of the haemagglutination test against the wild type, alpha, beta, gamma, and delta variants using pre- and post-vaccination sera. The sera were diluted 2-fold for 6 dilutions. CR033 and EY-6A are used are positive control, and red blood cells from blood group O negative are used as negative control. C Heat map showing collated data of HAT titres against the wild type, alpha, beta, gamma, and delta variants in pre- and post-vaccination sera. D Magnitude of neutralisation activity against the beta, D614G, and delta variants in pre- and post-vaccination sera. E Number of individuals with neutralisation activity against Beta or D614G or Delta variants in pre- and post-vaccination sera. Statistics were calculated using RM one-way ANOVA and p values adjusted for multiple comparison using Holm-Šídák’s multiple comparisons test. A p < 0.05 was regarded as statistically significant. S, full length Spike; RBD, receptor-binding domain; HAT, haemagglutination test; NC, negative control; PC, positive control; SARS-CoV-2, severe acute respiratory syndrome coronavirus