By Jonathan Stempel

(Reuters) -A federal judge ruled in favor of Merck (NSE: PROR ) in litigation accusing it of concealing the risks of Gardasil, a vaccine to prevent cervical and other cancers caused by the human papillomavirus and one of the drugmaker’s best-selling products.

The decision made public on Tuesday by U.S. District Judge Kenneth Bell in Charlotte, North Carolina applies to more than 200 lawsuits in the nationwide case.

So-called bellwether plaintiffs who received Gardasil between 2012 and 2021 said the vaccine caused them to suffer excessive increases in heart rates or premature ovarian failure, and that Merck should have added warnings to the labels.

But the judge said that by 2013, the latest the plaintiffs said warnings were needed, Merck and scientists had only a "paucity" of evidence suggesting a causal connection between Gardasil and the alleged symptoms.

He said that meant the Rahway, New Jersey-based drugmaker had no authority to add the requested warnings under federal law, which preempted the plaintiffs’ state law-based failure-to-warn claims.

"Federal law requires more than speculative inferences prior to adding dire warnings to lifesaving vaccines that discourage their use," Bell wrote in a 35-page decision. "That evidence is lacking here."

A lawyer for some plaintiffs had no immediate comment, having yet to review the decision.

Merck said it was "extremely pleased," and that Gardasil remains safe and effective "as reflected in its label."

Gardasil and Gardasil 9 are together Merck’s second best-selling product, with global sales of $8.58 billion in 2024. U.S. patent protection expires in 2028.

The U.S. Centers for Disease Control and Prevention recommend Gardasil for 11- and 12-year-olds to prevent cervical and other cancers caused by the human papillomavirus.

Nearly 160 million doses were distributed in the United States through the end of 2022, federal data show. The vaccine was first approved in the U.S. in 2006.

U.S. Health and Human Services Secretary Robert F. Kennedy Jr., a longtime vaccine skeptic, had been a lawyer of record for the plaintiffs in some Gardasil cases against Merck, though he is no longer involved.

The case is In re Gardasil Products Liability Litigation, U.S. District Court, Western District of North Carolina, No. 22-md-03036.