Challenge of conducting a placebo-controlled randomized efficacy study for influenza vaccine in a season with low attack rate and a mismatched vaccine B strain: a concrete example.

ABSTRACT:

Background

Our aim was to determine the efficacy of a trivalent inactivated split virus influenza vaccine (TIV) against culture-confirmed influenza A and/or B in adults 18 to 64 years of age during the 2005/2006 season in the Czech Republic.

Methods

6203 subjects were randomized to receive TIV (N = 4137) or placebo (N = 2066). The sample size was based on an assumed attack rate of 4% which provided 90% power to reject the hypothesis that vaccine efficacy (VE) was > or = 45%. Cases of influenza like illness (defined as fever (oral temperature > or =37.8 degrees C) plus cough and/or sore throat) were identified both by active (biweekly phone contact) and passive (self reporting) surveillance and nasal and throat swabs were collected from subjects for viral culture.

Results<

SUBMITTER: Beran J 

PROVIDER: S-EPMC2639595 | biostudies-literature | 2009 Jan

REPOSITORIES: biostudies-literature