Table 2.
Vaccine efficacy in the per-protocol population*
|
LAIV (n=1174) |
Placebo (n=587) |
Vaccine efficacy (95% CI) | |||
|---|---|---|---|---|---|
| Number of infections | Attack rate (%) | Number of infections | Attack rate (%) | ||
| Whole study population (n=1761) | |||||
| All vaccine-matched strains | 79 | 6·7% | 93 | 15·8% | 57·5% (43·6 to 68·0) |
| All strains | 170 | 14·5% | 144 | 24·5% | 41·0% (28·0 to 51·6) |
| H1N1 | 21 | 1·8% | 21 | 3·6% | 50·0% (9·2 to 72·5) |
| H3N2 | 57 | 4·9% | 72 | 12·3% | 60·4% (44·8 to 71·6) |
| B/Yamagata (vaccine-matched) | 2 | 0·2% | 1 | 0·2% | 0% (−1001·0 to 90·9) |
| B/Victoria (unmatched) | 58 | 4·9% | 31 | 5·3% | 6·5% (−43·0 to 38·8) |
| Kamalapur (n=1200)† | |||||
| All vaccine-matched strains | 56 | 7·0% | 52 | 13·0% | 46·2% (23·0 to 62·4) |
| With history of asthma or wheeze‡ | 22 | 8·9% | 17 | 12·6% | 29·0% (−29·0 to 60·9) |
| Without history of asthma or wheeze | 34 | 6·1% | 35 | 13·2% | 53·4% (27·2 to 70·3) |
| All strains | 103 | 12·9% | 79 | 19·8% | 34·8% (14·8 to 50·1) |
| Matlab (n=561)§ | |||||
| All vaccine-matched strains | 23 | 6·1% | 41 | 21·9% | 72·0% (54·7 to 82·6) |
| All strains | 67 | 17·9% | 65 | 34·8% | 48·5% (30·9 to 61·5) |
LAIV=live attenuated influenza vaccine.
*
Includes laboratory-confirmed influenza infections occurring from 8 days onwards after receiving vaccine or placebo.
†
n=800 in the LAIV group, n=400 in the placebo group.
‡
Vaccine efficacy analyses including history of asthma or wheezing could only be interpreted for the Kamalapur study site where history was identified at baseline. No participants at the Matlab site indicated a history of asthma or wheeze.
§
n=347 in the LAIV group, n=187 in the placebo group.