Between Jan 24 , 2007 , and Sept 19 , 2007 , 801 participants ( 267 % ) of a planned 3000 were randomly assigned ( 400 to vaccine , 401 to placebo ) ; 216 ( 27 % ) received only one injection , 529 ( 66 % ) received only two injections , and 56 ( 7 % ) received three injections .