Multiple lawsuits are making their way through the court system alleging that Merck's blockbuster vaccine for shingles isn't safe, and could cause serious adverse effects. Plaintiffs in the state of Pennsylvania, and elsewhere, allege that Zostavax isn't safe, and are taking to both the state and federal court system to seek justice.

According to Marc Bern of Marc J. Bern & Partners, there have been "thousands of complaints" about Zostavax in Pennsylvania alone. Patient injuries from the vaccine, he says, range from shingles itself, which the vaccine is supposed to prevent, to serious personal injuries such as blindness and paralysis. Other reports of adverse effects from Zostavax include brain damage and death.

"I think Merck has failed terribly … to warn about the very serious side effects and the failure of the vaccine to do what they claim it does," Bern told FiercePharma.