Merck’s Zostavax draws new litigation from patients alleging they contracted shingles

Merck faces a new liability lawsuit for shingles vaccine Shingrix.

Even as Merck & Co. confronts the prospect of a tough market competitor in GlaxoSmithKline’s Shingrix, the drugmaker’s shingles vaccine Zostavax faces a growing challenge in court.

Eighteen patients have filed a liability lawsuit against Merck, alleging the company produced and sold an “unreasonably dangerous vaccine” that caused serious injuries after vaccination. Hailing from a range of states including Louisiana, South Carolina, Tennessee, Michigan and Wisconsin, the plaintiffs filed their suit in Merck’s home state of New Jersey.

Instead of preventing shingles, Zostavax caused the plaintiffs to "contract a persistent strain of herpes zoster," according to the suit, resulting in painful outbreaks, hospital visits and post-herpetic neuralgia in two cases.

“Merck knew, or should have known, that its product caused viral infection, and was therefore not safe for administration to consumers,” the suit says.

RELATED: Zostavax patients sue Merck, claiming shingles shot caused injuries and death

In response, a Merck representative told FiercePharma the company "stands behind the demonstrated safety and efficacy" of its shot, which is licensed in 50 countries.

“Nothing is more important to Merck than the safety of our medicines and vaccines,” she said via email. Merck has distributed more than 36 million doses of the shot since its 2006 approval, and a CDC committee continues to recommend its use, she added.

“The company has continuously provided appropriate and timely information about Zostavax to consumers and to the medical, scientific and regulatory communities,” according to Merck’s statement.

Filed July 11, the new suit's allegations include negligence, defective design, failure to warn, breach of express and implied warranties, misrepresentation involving risk of physical harm and unjust enrichment. The plaintiffs are calling for a jury trial and a judgment to include damages.

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Earlier this year, a separate group of patients and their families sued for a range of alleged complications from vaccination. At the time, attorney Marc Bern told FiercePharma there were “thousands of complaints” yet to be filed. Bern’s firm is handling the latest legal action.

“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 said in March.

Zostavax pulled in $749 million in sales last year for Merck, but a challenger awaits from GlaxoSmithKline. Analysts have predicted that GSK’s shot, Shingrix, will grow to $1 billion in sales by 2022 as that company works to wrangle market share and drive uptake.

GSK filed for U.S. approval with that shot last fall and could secure approval later this year.