Merck & Co. Inc.'s animal vaccine facility in the Elkhorn area is becoming one of the multinational company's worldwide centers of research and development and a high-volume manufacturing operation. The Whitehouse Station, N.J.-based company spent $13.5 million over the past 16 months to expand and renovate the plant at 10488 S. 136th St., adding equipment that includes a high-speed vaccine vial filling line that is the only one of its kind in North America. Over the next several months 11 research scientists will transfer to the area from Delaware to expand the facility's research activity.