Plaintiffs suing Merck over its shingles vaccine Zostavax have lost a fight to have their cases heard in state court, after a judge determined one of the defendants had been fraudulently joined.

U.S. District Judge Harvey Bartle of the Eastern District of Pennsylvania on May 26 rejected attempts by 10 plaintiffs to have their cases remanded to the Philadelphia Court of Common Pleas.

Although many of the cases had initially been filed in state court, Bartle determined that a Merck employee and Pennsylvania resident had been improperly joined into the case in an effort to allow for state-court jurisdiction over the claims against Merck, a New Jersey company. Specifically, Bartle noted that plaintiffs had previously stipulated to dismiss claims against the Merck employee, Ann Redfield, in a case called Juday v. Merck. That case, which was the first to be filed in Pennsylvania over Zostavax, had been filed by an out-of-state plaintiff, so Redfield's participation in that case would not have affected jurisdiction.