Merck Wins Antitrust Immunity in Mumps Vaccine Case, U.S. Court Rules

Merck & Co. has been granted immunity from an antitrust lawsuit accusing the pharmaceutical giant of misleading regulators about the effectiveness of its mumps vaccine in order to stifle competition, a U.S. federal appeals court ruled on Monday. The decision, handed down by a 2-1 panel from the 3rd U.S. Circuit Court of Appeals, found that Merck is protected under a legal doctrine known as Noerr-Pennington immunity, according to Reuters. This doctrine shields companies from antitrust liability when they petition the government, even if their actions potentially limit competition.

The lawsuit, originally filed in 2012 by a group of doctors and medical practices, alleged that Merck engaged in deceptive practices to maintain its dominance in the mumps vaccine market, causing healthcare providers to overpay for the vaccine. Merck and the plaintiffs’ legal team did not immediately respond to requests for comment following the court’s decision, per Reuters.

New Jersey-based Merck had been the exclusive provider of the mumps vaccine in the U.S. from 1967 until 2022, offering it as part of its widely used MMR-II vaccine, which also protects against measles and rubella. Another combination vaccine, ProQuad, which includes protection against chickenpox, was also part of Merck’s portfolio.

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The dispute stems from concerns raised in the late 1990s by the U.S. Food and Drug Administration (FDA) over the mumps vaccine’s effectiveness. The FDA noted that the vaccine’s potency waned toward the end of its 24-month shelf life, prompting Merck to take corrective measures, according to the lawsuit. The plaintiffs claim that Merck responded by increasing the vaccine’s initial potency but used flawed clinical trials to demonstrate its ongoing efficacy. This allegedly led the company to conceal problems from the FDA, resulting in approval of its updated vaccine without revising its efficacy claims.

The plaintiffs further argued that this alleged deception had broader implications on market competition. Specifically, they claimed that British pharmaceutical company GlaxoSmithKline (GSK) chose not to develop its own mumps vaccine after believing it would be unable to match the effectiveness of Merck’s product. GSK, which is not a party in the lawsuit, only revisited its vaccine development efforts after learning of the alleged deficiencies in Merck’s clinical trials, according to Reuters.

The legal principle of Noerr-Pennington immunity played a pivotal role in the court’s decision. This doctrine, established in U.S. antitrust law, holds that entities cannot be held liable for anti-competitive behavior when lobbying or petitioning the government for policy decisions, even if the result curtails competition.

With this ruling, Merck has successfully avoided facing antitrust claims in this case.

Source: Reuters