(Reuters) - U.S. health regulators denied approval for Dynavax Technologies Inc's adult hepatitis B vaccine and sought additional data to evaluate its safety, delaying the market entry of a faster-acting and less frequently needed vaccine for the liver-attacking infection. The rejection of Heplisav - Dynavax's most advanced clinical candidate - sent the company's shares down as much as 38 percent to $1.84 before the bell on Monday. The U.S. ...