Table 4.
Seroconversion rates, anti-S IgG concentrations, and neutralising antibody titres.
| Dose |
p-value | ||||
|---|---|---|---|---|---|
| 1.0 μg N = 42 | 10.0 μg N = 23 | 1.0 μg followed by 10.0 μg N = 188 | |||
| Binding antibody by ELISA (ng/ml) | |||||
| Week 2 post-vaccine 1 | Seroconversion, n (%) | 3 (7%) | 0 (0%) | 2 (1%) | – |
| GM titre (95% CI) | 77 (47–124) | – | 655 (20–21469) | – | |
| Vaccine 2 | Seroconversion, n (%) | 8 (19%) | 8 (35%) | 17 (9%) | – |
| GM titre (95% CI) | 164 (83–325) | 258 (139–479) | 470 (266–830) | – | |
| Week 2 post-vaccine 2 | Seroconversion, n (%) | 18 (43%) | 14 (61%) | 147 (80%) | 0.057 |
| GM titre (95% CI) | 251 (184–343) | 500 (233–1076) | 1224 (1008–1486) | 0.010 | |
| Week 4 post-vaccine 2 | Seroconversion, n (%) | 20 (48%) | 13 (57%) | 143 (80%) | 0.016 |
| GM titre (95% CI) | 262 (186–367) | 508 (199–1294) | 1294 (1065–1573) | 0.010 | |
| Neutralising antibody (NT50) | |||||
| Week 2 post-vaccine 2 | Seroconversion, n (%) | 14 (33%) | 10 (43%) | 102 (56%) | 0.277 |
| GM dilution (95% CI) | 46 (31–70) | 70 (27–180) | 68 (53–86) | 0.928 | |
| Week 4 post-vaccine 2 | Seroconversion, n (%) | 7 (17%) | 12 (52%) | 99 (56%) | 0.825 |
| GM dilution (95% CI) | 30 (11–83) | 124 (50–306) | 75 (56–102) | 0.297 | |
1.0 μg and 10.0 μg doses assessed in dose-ranging cohort; 1.0 μg followed by 10.0 μg dose assessed in expanded safety cohort. GM, geometric mean. Calculated among seroconversion samples. Fisher's exact and t-tests used to compare seroconversion rates and geometric means among responders, respectively. P-values detail comparison between 10.0 μg and 1.0 μg followed by 10.0 μg groups. Missing values for binding antibody: 1.0 μg followed by 10.0 μg (week 2 post-vaccine 1, n = 3). Removed samples for binding antibody: 1.0 μg followed by 10.0 μg (vaccine 2, COVID infection n = 2). Missing values for binding and neutralising antibody: 1.0 μg followed by 10.0 μg (week 2 post-vaccine 2, n = 2; week 4 post-vaccine 2, n = 5). Removed samples for binding and neutralising antibody: 1.0 μg followed by 10.0 μg (week 2 post-vaccine 2, COVID infection n = 3; week 4 post-vaccine 2, COVID infection n = 3, authorised vaccine n = 2). Note: Among baseline convalescent samples GM binding titre (95% CI) was 650 (457–925) and GM NT 50 (95% CI) was 85 (56–129). Significant value ≤0.05 is shown in bold.