Shares in Intercell AG plunged 25 percent Monday after an independent data monitoring committee called for a halt in recruitment for a pivotal Phase II/III trial of a vaccine designed to prevent nosocomial Staphylococcus aureus infection. Although the vaccine, which is partnered with Merck & Co. Inc., did not meet pre-specified futility criteria in an interim analysis, the committee wants additional risk-benefit analyses to be conducted before dosing can resume.