Figure 4.

Neutralising antibody response measured by pseudovirus-based neutralisation assay (PBNA). Geometric mean neutralising antibody titres were compared from baseline (day 0) to day 56 (28 days after the second dose). The serum neutralisation titres were defined as the 50% maximal inhibitory concentration (IC₅₀). The titres of neutralisation assay were converted to international unit (IU)/mL using WHO international standard (NIBSC 20/136) and compared with the HCS of WHO representative panel. GMT, Geometric mean titre; SD, standard deviation; SCR, seroconversion rate; NIBSC, National Institute for Biological Standards and Control; HCS, human convalescent serum.