Table 2.
Attack rates and TIV efficacy for culture confirmed influenza in adults (total cohort for efficacy)
| Type of culture confirmed | Trivalent inactivated split virus influenza vaccine N = 4137 |
Placebo N = 2066 |
Vaccine efficacy (1-RR) | |||||
|---|---|---|---|---|---|---|---|---|
| Number of cases | % Attack rate | Number of cases | % Attack rate | % | 95% CI† | P value † | ||
| LL | UL | |||||||
| Any | 28 | 0.7 | 18 | 0.9* | 22.3 | -49.1 | 58.5 | 0.433 |
| Influenza A | 6 | 0.1 | 4 | 0.2 | 25.1 | -260.9 | 82.2 | 0.740 |
| Influenza B | 22 | 0.5 | 14 | 0.7 | 21.5 | -65.9 | 61.6 | 0.481 |
* Sample size calculation was based on expected attack rate of at least 4% in the placebo group
† Two-sided Fisher Exact test, the 95% confidence intervals for vaccine efficacy was calculated using a conditional exact method.