TABLE 2.
Comparison of immune response to the Vi capsular polysaccharide vaccine and the control hepatitis A vaccine in children between the ages of 2 and 16 years in Karachi and Kolkata
| Variables | Values for children receiving the indicated vaccine |
P | |
|---|---|---|---|
| Vi | Hepatitis A | ||
| Overall (age 2–16 yr) | |||
| Blood sample 1, day 0 (prevaccination)a | |||
| No. | 153 | 147 | |
| GMCb (95% confidence limits) | 83.2 (78.4–88.4) | 81.8 (77.2–86.7) | 0.692 |
| Attained protective antigen level (n [%])c | 12 (7.8) | 10 (6.8) | 0.723 |
| Blood sample 2, 6 wk since vaccination | |||
| No. | 123 | 120 | |
| GMC (95% confidence limits) (ELU/ml) | 1,428.3 (1130–1805.4) | 85.9 (78–94.6) | <0.001 |
| Attained protective antigen level (n [%]) | 117 (95.1) | 9 (7.5) | <0.001 |
| Achieved a ≥4-fold rised (n [%]) | 104 (86.7) | 2 (1.7) | <0.001 |
| Blood sample 3, 2 yr since vaccination | |||
| No. | 71 | 68 | |
| GMC (95% confidence limits) (ELU/ml) | 262.6 (190–362.8) | 90.4 (79.1–103.4) | <0.001 |
| Attained protective antigen level (n [%]) | 40 (56.3) | 8 (11.8) | <0.001 |
| Achieved a ≥4-fold rise (n [%]) | 27 (39.1) | 4 (6.1) | <0.001 |
| Age <5 yr | |||
| Blood sample 1, day 0 (prevaccination) | |||
| No. | 60 | 52 | |
| GMC (95% confidence limits) (ELU/ml) | 75 (75–75) | 76.2 (73.8–78.7) | 0.304 |
| Attained protective antigen level (n [%]) | 0 (0.0) | 1 (1.9) | e |
| Blood sample 2, 6 wk since vaccination | |||
| No. | 42 | 39 | |
| GMC (95% confidence limits) (ELU/ml) | 832.2 (546–1268.5) | 82.7 (67.8–100.8) | <0.001 |
| Attained protective antigen level (n [%]) | 36 (85.7) | 1 (2.6) | <0.001 |
| Achieved a ≥4-fold rise (n [%]) | 29 (70.7) | 1 (2.7) | <0.001 |
| Blood sample 3, 2 yr since vaccination | |||
| No. | 21 | 19 | |
| GMC (95% confidence limits) (ELU/ml) | 133.4 (93.7–190) | 96.5 (67–139) | 0.218 |
| Attained protective antigen level (n [%]) | 8 (38.1) | 2 (10.5) | 0.071 |
| Achieved a ≥4-fold rise (n [%]) | 5 (25.0) | 2 (11.1) | 0.379 |
| Age 5–15.9 yr | |||
| Blood sample 1, day 0 (prevaccination) | |||
| No. | 93 | 95 | |
| GMC (95% confidence limits) (ELU/ml) | 89 (80.8–98.1) | 85.1 (77.9–92.9) | 0.497 |
| Attained protective antigen level (n [%]) | 12 (12.9) | 9 (9.5) | 0.463 |
| Blood sample 2, 6 wk since vaccination | |||
| No. | 81 | 81 | |
| GMC (95% confidence limits) (ELU/ml) | 1,890 (1447.3–2468.1) | 87.5 (78.5–97.6) | <0.001 |
| Attained protective antigen level (n [%]) | 81 (100.0) | 8 (9.9) | e |
| Achieved a ≥4-fold rise (n [%]) | 75 (94.9) | 1 (1.3) | <0.001 |
| Blood sample 3, 2 yr since vaccination | |||
| No. | 50 | 49 | |
| GMC (95% confidence limits) (ELU/ml) | 348.9 (230.2–528.8) | 88.2 (77.3–100.5) | <0.001 |
| Attained protective antigen level (n [%]) | 32 (64.0) | 6 (12.2) | <0.001 |
| Achieved a ≥4-fold rise (n [%]) | 22 (44.9) | 2 (4.2) | <0.001 |
a
Blood sample 1 is from day 0 (prevaccination), 2 is from week 6 since vaccination, and 3 is from year 2 since vaccination.
b
GMC, geometric mean concentration. All values are expressed in ELU/ml.
c
Attained protective antigen level (Vi, ≥150 ELU/ml [GSK in-house standard]). We used the value 75 ELU/ml (midpoint) for those listed as <150 ELU/ml in the report.
d
Achieved a ≥4-fold rise in antibodies, in relation to baseline, as detected in the cited blood sample.
e
P value is not possible due to 0 in one of the cells.