title: A procedure for group sequential comparative poisson trials.
abstract: This paper develops a group sequential procedure for comparative Poisson trials that are commonly used in vaccine studies. This procedure is based on exact conditional binomial distributions of number of events from the treated subjects conditional on total numbers of events at each interim analysis stage. We show that this procedure (vs. non interim analysis) can greatly reduce the trial length when the null hypothesis is false. We also discuss the impact of number of interim analyses, different alpha spending functions, and the discreetness of binomial distribution on the efficiency of this procedure. Corresponding Splus programs were also developed.
authors: Genentech Inc., South San Francisco 94080, USA. qxia@gene.com
authors: Qi
authors: Q
authors: Xia
authors: Donald R
authors: DR
authors: Hoover
mesh_terms: D000465:Algorithms; D016010:Binomial Distribution; D006801:Humans; D016012:Poisson Distribution; D012107:Research Design; D014612:Vaccines / Q000009:adverse effects / Q000627:therapeutic use*
chemical_list: D014612:Vaccines