Influenza vaccine studies

Influenza vaccine
FLUBLOK® FDA Package Insert
Description
Clinical Pharmacology
Indications and Usage
Contraindications
Warnings and Precautions
Adverse Reactions
Clinical Studies
Dosage and Administration
How Supplied
Labels and Packages

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mohamed Moubarak, M.D. [2]

Clinical Studies

Efficacy Against Culture-Confirmed Influenza

The efficacy of Flublok was evaluated in a randomized, observer-blind, placebo-controlled multicenter trial conducted in the U.S. during the 2007-2008 influenza season (Study 1). The study enrolled and vaccinated 4648 healthy adults (mean age 32.5 years) randomized in a 1:1 ratio to receive a single dose of Flublok (n=2344) or saline placebo (n=2304). Among enrolled subjects, 59% were female, 67% were white, 19% African-American, 11% Latino/Hispanic, 2% Asian and < 1% other. The two groups were similar in demographics. Culture-confirmed influenza was assessed by active and passive surveillance for influenza-like illness (ILI) beginning 2 weeks post-vaccination until the end of the influenza season, approximately 7 months post- vaccination. ILI was defined as having at least 2 of 3 symptoms (no specified duration) in the following categories: 1) fever ≥ 100ºF; 2) respiratory symptoms (cough, sore throat, runny nose/stuffy nose); or 3) systemic symptoms (myalgias, arthralgias, headache, chills/sweats, tiredness/malaise). For subjects with an episode of ILI, nasal and throat swab samples were collected for viral culture.

The primary efficacy endpoint was Centers for Disease Control-defined influenza-like illness (CDC-ILI) with a positive culture for an influenza virus strain antigenically resembling a strain represented in Flublok. CDC-ILI is defined as fever of ≥100°F oral accompanied by cough, sore throat, or both on the same day or on consecutive days (1). Attack rates and vaccine efficacy (VE), defined as the relative reduction in the influenza rate for Flublok relative to placebo, were calculated for the total vaccinated cohort (n=4,648). The pre-defined success criterion for the primary efficacy analysis was that the lower bound of the 95% confidence interval (CI) of VE should be at least 40%. Vaccine efficacy against antigenically matched culture-confirmed CDC-ILI could not be determined reliably because 96% of the influenza isolates obtained from subjects in Study 1 were not antigenically matched to the strains represented in the vaccine. An exploratory analysis of VE of Flublok against all strains regardless of antigenic match isolated from any subject with an ILI, not necessarily CDC-defined ILI, demonstrated an efficacy estimate of 44.8% (95% CI 24.4, 60.0). See Table 2 for a presentation of VE by case definition and antigenic similarity.

References

Adapted from the FDA Package Insert.