GlaxoSmithKline plans a 12% (or 1,800) reduction in its U.S. sales force as part of a restructuring effort. The company plans to shift some sales representatives from its pharmaceutical unit to its vaccine unit, which will result in a reduction of about 1,000 employees. That will leave it with a U.S. sales force of about 7,500 by the end of the year.     As part of the restructuring, the company plans to group its sales staff around specific treatment areas such as respiratory, for the asthma...