UPDATE 1-Dynavax's flu vaccine shows promise, shares rise

* Plans to initiate early-stage trial by mid-year

* Shares up 13 pct in after-market

April 26 (Reuters) - Dynavax Technologies Corp (DVAX.O) said its vaccine against flu showed positive response in a preclinical study, sending its shares up 13 percent.

Dynavax's vaccine enhances the efficacy of a standard flu vaccine by increasing antibody production, the company said.

The company plans to initiate early-stage clinical development of its universal flu vaccine by mid-year 2010.

Shares of the company were up 16 cents at $1.60 in after-market trade. They closed at $1.44 Monday on Nasdaq. (Reporting by Anand Basu in Bangalore; Editing by Don Sebastian)