(S (S (BASENP (DT The) (NN study)) (VP (MD will) (VP (VB examine) (SBAR (IN if) (S (BASENP (DT the) (NN vaccine)) (VP (VP (VBZ prevents) (BASENP (NN infection))) (CC or) (VP (VBZ lowers) (NP (BASENP (NN HIV) (NNS levels)) (PP (IN in) (NP (BASENP (DT those)) (SBAR (WHNP (WP who)) (S (VP (VBP do) (VP (VB get) (VP (VBN infected)))))))))))))))) (PERIOD .))