By Mackenzie Tatananni

In a sudden reversal of fortune, Moderna stock snapped a six-day winning streak on Monday to become one of the worst-performing stocks in the S&P 500.

The biotech's shares plunged 6.8% to $59.61, vastly underperforming the broader market's 0.3% dip. Before hitting a wall, the stock had been riding high, getting its latest boost this past Thursday after a Food and Drug Administration committee unanimously voted that the benefits of Moderna's seasonal flu vaccine outweighed the risks in patients aged 50 and older.

The rally began in earnest on June 11 after Moderna was cleared to launch a U.K. study of its mRNA-based vaccine for patients with Lynch Syndrome. The inherited condition occurs when genetic mutations prevent cells from repairing their own DNA, causing errors to build up and leading to cancer.

No such therapies exist on the market today, making the nod from regulators a resounding validation of cancer vaccines, which have recently evolved from a far-off medical concept into a feasible reality.

Other catalysts have helped the stock gain momentum. On June 16, Moderna announced a leadership restructuring to prepare for an upcoming wave of product launches. The stock climbed even higher after the FDA released briefing documents that suggest the agency is likely to approve Moderna's mRNA-based flu shot.

The company's flagship mRNA technology, which teaches the body's own cells to make proteins, has faced pushback from officials including Health Secretary Robert F. Kennedy Jr., who once proclaimed that the technology "poses more risks than benefits" for respiratory viruses.

Although the scientific community regards it as a safe and effective platform for vaccines and therapeutics, its initial regulatory approval sparked controversy among critics who argued it was fast-tracked. These lingering doubts have cast a long shadow over Moderna's reputation.

The FDA, under former Center for Biologics Evaluation and Research Director Vinay Prasad, said in February that it would not review the flu shot. The agency changed its tune just two days later.

Without a clear impetus, Moderna shares may be losing momentum as the trickle of recent catalysts peters out. While the stock has more than doubled this year, Moderna has struggled to shake its reputation as an unprofitable Covid vaccine play. Wall Street is eagerly looking ahead to Moderna's next big money-maker, as many expect its burgeoning oncology effort to drive future growth.

The stock has rallied on far less substance before. In May, a Hantavirus outbreak had investors betting on the drugmaker to develop a vaccine, sending shares higher. Don't assume this hot streak is over just yet.

Write to Mackenzie Tatananni at mackenzie.tatananni@barrons.com

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June 22, 2026 13:46 ET (17:46 GMT)

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