Table 1.
Meta-analysis results comparing primary outcome (RT-PCR and/or culture) with secondary outcome (RT-PCR and/or culture and/or HAI assay) for all ages
| Type of influenza | # of influenza seasons | Sample size (placebo group) | # of influenza cases (placebo group) | Natural attack rate % (lower 95% CI, upper 95% CI) | I 2 |
|---|---|---|---|---|---|
| Primary outcome (PCR and/or viral culture) | |||||
| All | 37 | 39115 | 1774 | 7.86 (5.48, 10.23) | 99.86% |
| Influenza A | 34 | 38360 | 1303 | 5.68 (3.71, 7.65) | 99.69% |
| Influenza B | 35 | 38854 | 491 | 1.87 (1.02, 2.72) | 99.87% |
| Secondary outcome (PCR and/or viral culture and/or HAI assay) | |||||
| All | 47 | 41212 | 2055 | 9.84 (7.06, 12.62) | 99.77% |
| Influenza A | 41 | 40074 | 1505 | 6.96 (4.49, 9.42) | 99.80% |
| Influenza B | 42 | 40568 | 536 | 2.57 (1.45, 3.70) | 99.93% |
Abbreviations: CI confidence interval, HAI haemagglutination inhibition assay, RT-PCR reverse transcription polymerase chain reaction.