(Corrects Boryung representation of Sinovac in paragraph 6, Sinovac share trading status in paragraph 12) * Boryung shares up as much as 15 pct * Says final size of deal undecided * Says Sinovac can supply 10 mln doses * Sinovac says talk is "premature," denies volume By Shin Jieun and Lucy Hornby SEOUL/BEIJING, Sept 1 (Reuters) - Shares in South Korea's Boryung Pharm &LT003850.KS> soared to a 14-month high on Tuesday on news it would acquire supplies of H1N1 flu vaccine from China's Sinovac &LTSVA.A>, though Sinovac said it had merely agreed that Boryung would be its agent in the South Korean market. "Details of the deal have not yet been decided and will be specified when South Korean health authorities approve the deal," a Boryung spokesman told Reuters, adding Sinovac could supply 10 million doeses or more.