Table 5.
Vaccine efficacy against culture-confirmed influenza in healthy adults 18–49 years of age.
| Case definition | Flublok (N = 2344) |
Saline Placebo (N = 2304) |
Flublok vaccine efficacy*, % | 95% confidence interval | ||
|---|---|---|---|---|---|---|
| Cases, n | Rate, % | Cases, n | Rate, % | |||
| Positive culture with a strain represented in the vaccine | ||||||
| CDC-ILI, all matched strains$ | 1 | 0.04 | 4 | 0.2 | 75.4 | (−148.0, 99.5) |
| Any ILI, all matched strains‡ | 2 | 0.1 | 6 | 0.3 | 67.2 | (−83.2, 96.8) |
| Positive culture with any strain, regardless of match to the vaccine | ||||||
| CDC-ILI, all strains$ | 44 | 1.9 | 78 | 3.4 | 44.6 | (18.8–62.6) |
| Subtype A | 26 | 1.1 | 56 | 2.4 | 54.4 | (26.1–72.5) |
| Type B | 18 | 0.8 | 23 | 1.0 | 23.1 | (−49.0, 60.9) |
| Any ILI, all strains‡ | 64 | 2.7 | 114 | 4.9 | 44.8 | (24.4–60.0) |
| Subtype A | 41 | 1.7 | 79 | 3.4 | 49.0 | (24.7–65.9) |
| Type B | 23 | 1.0 | 36 | 1.6 | 37.2 | (−8.9, 64.5) |
*
Determined under the assumption of Poisson event rates, according to Breslow and Day [1987].
$
Meets Centers for Disease Control (CDC) influenza-like illness (ILI) defined as fever of at least 100°F oral accompanied by cough or sore throat, on the same day or on consecutive days.
‡
All culture-confirmed cases are considered, regardless of whether they qualified as CDC-ILI.