JULIE STEENHYSEN JOHNSON&JOHNSON is on track to roll out its single-shot coronavirus vaccine in March, and plans to have clear data on how effective it is by the end of this month or early February, the U.S. healthcare company's chief science officer said. Dr. Paul Stoffels in an interview also said J&J expects to meet its stated target of delivering one billion doses of its vaccine by the end of this year as the company ramps up production. The New York Times has reported that J&J was experiencing manufacturing delays that would reduce the number of doses initially available. Stoffels…