BUZZ-GlaxoSmithKline Plc: Shingles vaccine could be better than Merck's - Cowen

** Drugmaker's U.S.-listed shares up 1.3 pct at $46.75 premarket, London-listed up nearly 2 pct

** Cowen & Co analysts say GSK's vaccine to treat shingles may be more effective than Merck (LSE: 0O14.L - news) 's

** Glaxo's vaccine HZ/su should be well positioned to capture market share from Merck's Zostavax if final data from a late-stage study shows HZ/su has better efficacy while treating older patients, Cowen says

** Final data from late-stage study expected in H1 2015

** Merck sold $765 mln worth Zostavax worldwide in 2014

** Barclays (LSE: BARC.L - news) raised its price target on European drugmakers, including GSK's London-listed stock

** GSK up nearly 2 pct on the LSE

** Through Monday, the U.S. stock had gained 10 pct since Dec. 18, when GSK reported early data from the late-stage study