Table 2. Results of Serum Antibody Studies before and 3 Weeks after Each Dose in the Per-Protocol Population, According to Study Group*.
| ELISA Result | Vaccine† | Placebo | ||||
|---|---|---|---|---|---|---|
| Day 0 (N =37) | Day 21 (N=38) | Day 42 (N=38) | Day 0 (N =39) | Day 21 (N=39) | Day 42 (N=39) | |
| Total serum antibody (IgG, IgA, and IgM) ELISA | ||||||
| GMT (95% CI) | 3500 (2100–5700) | 6900 (4200–11,100) | 16,500 (10,800–25,100) | 4700 (3000–7300) | 5000 (3100–8000) | 4900 (3100–7800) |
| Seroresponse — % (95% CI) | NA | 30 (16–47) | 70 (53–84) | NA | 3 (0–14) | 3 (0–14) |
| GMFR (95% CI) | NA | 2.0 (1.6–2.6) | 4.9 (3.6–6.8) | NA | 1.1 (0.9–1.2) | 1.1 (0.9–1.2) |
| IgG ELISA | ||||||
| GMT (95% CI) | 3.2 (1.8–5.6) | 6.5 (4.1–10.4) | 14.1 (9.5–21.1) | 4.6 (2.9–7.3) | 4.5 (2.8–7.0) | 4.8 (3.1–7.4) |
| Seroresponse — % (95% CI) | NA | 16 (6–32) | 49 (32–66) | NA | 0 (0–9) | 0 (0–9) |
| GMFR (95% CI) | NA | 2.0 (1.6–2.6) | 4.5 (3.1–6.5) | NA | 1.0 (0.9–1.0) | 1.0 (1.0–1.1) |
| IgA ELISA | ||||||
| GMT (95% CI) | 1.0 (0.5–1.9) | 3.4 (1.9–6.0) | 7.4 (4.2–13.1) | 1.2 (0.7–2.1) | 1.1 (0.7–2.0) | 1.2 (0.7–2.2) |
| Seroresponse — % (95% CI) | NA | 43 (27–61) | 70 (53–84) | NA | 0 (0–9) | 0 (0–9) |
| GMFR (95% CI) | NA | 3.4 (1.9–6.0) | 7.5 (4.6–12.2) | NA | 0.9 (0.9–1.0) | 1.0 (0.9–1.1) |
| IgM ELISA | ||||||
| GMT (95% CI) | 28.5 (22.6–35.9) | 30 (22.3–40.4) | 91.3 (47.7–174.7) | 29.9 (23.2–38.4) | 29.9 (23.2–38.4) | 29.9 (23.2–38.4) |
| Seroresponse — % (95% CI) | NA | 3 (0–14) | 32 (18–50) | NA | 0 (0–9) | 0 (0–9) |
| GMFR (95% CI) | NA | 1.1 (1.0–1.2) | 3.3 (1.8–6.2) | NA | 1.0‡ | 1.0‡ |
| Histo-blood group antigen–blocking activity | ||||||
| GMT (95% CI) | 32.1 (22.9–44.9) | 59.0 (40.6–85.8) | 109.0 (71.7–165.6) | 39.3 (28.5–54.0) | 45.1 (32.1–63.4) | 47.1 (32.5–68.4) |
| Seroresponse — % (95% CI) | NA | 16 (6–32) | 32 (18–50) | NA | 5 (1–17) | 3 (0–14) |
| GMFR (95% CI) | NA | 1.9 (1.5–2.4) | 3.6 (2.8–4.7) | NA | 1.1 (1.0–1.4) | 1.2 (1.0–1.5) |
*
GMFR is the factor increase in the geometric mean titer (GMT) from baseline. A seroresponse was defined as an increase by a factor of 4 or more. ELISA denotes enzyme-linked immunosorbent assay, and NA not applicable.
†
Data for day 21 and day 42 in the vaccine group were available for 38 participants for GMT and 37 participants for all other values.
‡
The 95% CI could not be calculated.