Table 2:
Seroprotection, seroconversion, and median neutralising antibody titres for poliovirus type 2, by age
| mIPV2HD group |
IPV group |
Difference (95% CI) | p value | |||
|---|---|---|---|---|---|---|
| n/N | Outcome* | n/N | Outcome* | |||
| 6 weeks | ||||||
| Seroprotection | 71/114 | 62·3% (52·7–71·2) | 68/115 | 59·1% (49·6–68·2) | .. | .. |
|
| ||||||
| 14 weeks | ||||||
| Seroprotection | 44/115 | 38·3% (29·4–47·8) | 39/115 | 33·9% (25·3–43·3) | .. | .. |
|
| ||||||
| 15 weeks | ||||||
| Seroprotection | 114/115 | 99·1% (95·3–100·0) | 108/114 | 94·7% (88·9–98·0) | .. | .. |
| Seroconversion | 107/115 | 93·0% (86·8–96·9) | 87/114 | 76·3% (67·4–83·8) | 16·7 (3·7 to 29·1) | <0·0001 |
| Reciprocal titre | .. | 288 (90·5–910·2) | .. | 45 (18·0–144·0) | .. | .. |
|
| ||||||
| 18 weeks | ||||||
| Seroprotection | 113/115 | 98·3% (93·9–99·8) | 106/114 | 93·0% (86·6–96·9) | .. | .. |
| Seroconversion | 107/115 | 93·0% (86·8–96·9) | 86/115 | 74·8% (65·8–82·4) | 18·3 (5·0 to 31·1) | <0·0001 |
| Reciprocal titre | .. | 181 (72·0–362·0) | .. | 36 (18·0–113·8) | 98·8 (60·7 to 136·9) | <0·0001 |
|
| ||||||
| 19 weeks | ||||||
| Seroprotection | 111/112 | 99·1% (95·1–100·0) | 113/114 | 99·1% (95·2–100·0) | .. | .. |
| Seroconversion | 110/112 | 98·2% (93·7–99·8) | 104/114 | 91·2% (84·5–95·7) | 7·0 (−6·4 to 19·9) | 0·0338† |
| Seroconversion‡ | 1/2 | 50·0% (1·3–98·7) | 7/8 | 87·5% (47·3–99·7) | .. | .. |
| Reciprocal titre | .. | 362 (144·0–910·2) | .. | 181 (56·9–455·1) | .. | .. |
Seroprotection defined as neutralising titre of at least 8. Seroconversion assessed with respect to status at 14 weeks of age. For infants who were seronegative (titre <8), seroconversion was defined as achieving an antibody titre of at least 8; for infants who were seropositive (titre ≥8), seroconversion was defined as a titre four times higher than the expected fall in maternal antibody concentrations based on the prevaccination titre. Proportion of infants with seroconversion compared between groups using Fisher’s exact test. Median neutralising antibody titres compared between groups using the Mann-Whitney-Wilcoxon test. mIPV2HD=monovalent inactivated poliovirus vaccine, type 2, high dose. IPV=trivalent inactivated poliovirus vaccine. n=number of infants seroprotected or seroconverted. N=total number of infants at each timepoint.
Data for seroprotection and seroconversion are % (95% CI); data for reciprocal titre are median (IQR).
Exploratory analysis.
Seroconversion in infants seronegative at 18 weeks of age. Seroconversion was defined as achieving an antibody titre of at least 8.