MARIETTA, Pa. (AP) — London pharmaceutical giant GlaxoSmithKline says all of its U.S.-approved vaccines eventually will be processed at its new southeastern Pennsylvania plant. GlaxoSmithKline bought the closed Wyeth Laboratories plant at Marietta, 70 miles west of Philadelphia, in 2005 for $14 million. The company has spent more than $300 million to upgrade and expand capacity at the 90-acre complex. Vice President Peter Lammers of the company’s vaccines unit says the investment is expected to pay off because of the growth GlaxoSmithKline expects in vaccines in the United States. The plant is expected to employ up to 300 people and carry out cutting-edge vaccine development. The company’s Engerix-B hepatitis B prevention vaccine will be the first to be produced at Marietta, starting in April.