Pfizer Inc. said early Thursday that its phase 2 clinical trial for a C. difficile vaccine had positive results. The bacterium, which causes infectious diarrhea, typically affects older adults in medical facilities and can be life-threatening and difficult to treat. The vaccine was studied for safety, tolerability and immune response in more than 850 healthy older adults, and will proceed to a late-stage trial in the first half of this year, Pfizer said. The vaccine was designated for a fast track by the Food and Drug Administration in 2014, a label intended to facilitate innovation in difficult-to-treat areas. Pfizer shares were up 0.4% in pre-market trade Thursday. Shares have fallen 3.4% over the last three months, compared with a 7.4% rise in the S&P 500 .
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