Table 1.
Summary of Immune Responses Against Group B Streptococcus Serotypes
| Serotype | Day | Placeboa | GBS 0.5 μg | GBS 2.5 μg | GBS 5.0 μg | ||||
|---|---|---|---|---|---|---|---|---|---|
| No. | Value (95% CI) | No. | Value (95% CI) | No. | Value (95% CI) | No. | Value (95% CI) | ||
| GBS serotype Ia | |||||||||
| GMC | Birth | 73 | 0.49 (.34–.71) | 75 | 6.66 (4.03–11.0) | 76 | 6.52 (3.96–11.0) | 69 | 12.0 (7.21–20.0) |
| GMC | D43 | 71 | 0.31 (.23–.42) | 75 | 3.21 (2.01–5.13) | 76 | 2.95 (1.85–4.70) | 68 | 5.54 (3.38–9.06) |
| GMC | D91 | 75 | 0.38 (.29–.49) | 71 | 1.97 (1.31–2.95) | 75 | 2.22 (1.49–3.29) | 64 | 2.78 (1.81–4.26) |
| Ratio | D43:Birth | 68 | 0.67 (.58–.77) | 74 | 0.51 (.44–.58) | 75 | 0.47 (.41–.54) | 68 | 0.45 (.39–.52) |
| Ratio | D91:Birth | 71 | 0.81 (.63–1.05) | 70 | 0.31 (.25–.39) | 73 | 0.32 (.25–.40) | 63 | 0.26 (.20–.33) |
| GBS serotype Ib | |||||||||
| GMC | Birth | 62 | 0.21 (.14–.32) | 71 | 1.15 (.68–1.95) | 71 | 1.72 (1.02–2.92) | 66 | 1.39 (.81–2.40) |
| GMC | D43 | 69 | 0.15 (.11–.21) | 72 | 0.73 (.47–1.14) | 77 | 0.88 (.57–1.35) | 67 | 0.67 (.42–1.07) |
| GMC | D91 | 76 | 0.50 (.39–.63) | 74 | 0.85 (.61–1.18) | 73 | 1.08 (.77–1.51) | 66 | 0.83 (.59–1.19) |
| Ratio | D43:Birth | 57 | 0.82 (.62–1.08) | 69 | 0.61 (.51–.73) | 70 | 0.59 (.49–.71) | 64 | 0.52 (.43–.63) |
| Ratio | D91:Birth | 61 | 2.40 (1.68–3.43) | 69 | 0.76 (.53–1.08) | 67 | 0.69 (.49–.99) | 62 | 0.66 (.45–.95) |
| GBS serotype IIIb | |||||||||
| GMC | Birth | 52 | 0.29 (.19–.43) | 57 | 2.11 (1.26–3.54) | 64 | 2.30 (1.41–3.76) | 58 | 1.72 (1.03–2.87) |
| GMC | D43 | 63 | 0.16 (.12–.22) | 64 | 0.82 (.53–1.27) | 75 | 0.88 (.59–1.31) | 61 | 0.68 (.43–1.06) |
| GMC | D91 | 69 | 0.27 (.21–.34) | 63 | 0.60 (.42–.85) | 63 | 0.69 (.48–.98) | 57 | 0.51 (.35–.74) |
| Ratio | D43:Birth | 44 | 0.57 (.44–.73) | 48 | 0.49 (.39–.62) | 62 | 0.41 (.34–.50) | 51 | 0.44 (.36–.55) |
| Ratio | D91:Birth | 46 | 0.83 (.60–1.14) | 45 | 0.35 (.24–.49) | 53 | 0.29 (.21–.39) | 47 | 0.32 (.23–.45) |
Data are shown as antibody GMCs and GMC ratios at days 43 and 91 compared with baseline, by timepoint (per-protocol set).
Abbreviations: CI, confidence interval; D, day; GBS, group B Streptococcus; GMC, geometric mean concentration; No., number of infants with available results in each group.
aGBS-specific antibody geometric mean concentrations at birth were negligible in the placebo group and therefore ratios for this group are unreliable.
bGBS-specific antibody concentrations were assessed by priority ranking, following the order Ia > Ib > III. Due to limitations in serum volume, it was not possible for all sera to generate final results in all 3 serotype enzyme-linked immunosorbent assays.