Image Source: Unsplash
 

Moderna Inc. (MRNA) shares fell sharply on Monday, December 1, 2025, following revelations that the Food and Drug Administration plans to impose stricter requirements on vaccine approvals. The decline came after an internal FDA memo from senior official Vinay Prasad, seen by Bloomberg, outlined new safety testing protocols that will affect how vaccines reach the market.

The announcement triggered a broader sell-off across the vaccine sector, with multiple manufacturers experiencing significant stock declines as investors assessed the potential impact on future product pipelines and regulatory timelines.

Stricter Rules Threaten Moderna’s Flu and Combo Vaccine Plans
 

The timing of the FDA’s announcement is particularly significant for Moderna, which is currently developing both a standalone flu vaccine and a combination shot covering flu and COVID. The company recently indicated plans to file for regulatory approval for its flu vaccine in the US, Europe, Australia, and Canada by January 2026, while awaiting guidance from US officials before seeking approval for its combination vaccine.

William Blair analysts noted on Monday that Prasad’s memo suggests Moderna’s flu vaccine could face heightened safety scrutiny, potentially delaying or complicating the approval process.

Moderna’s stock has experienced substantial challenges over the past year, with a year-to-date return of negative 41.37% and a one-year return of negative 43.38%, significantly underperforming the S&P 500’s gains of 15.84% and 12.95% respectively.

The company reported revenue of $1.02 billion in Q3 FY25 but posted earnings losses of $200 million, reflecting ongoing financial pressures. With a market capitalization of approximately $9.5 billion and analysts setting an average price target of $37.21, the company faces considerable headwinds as it navigates both regulatory uncertainty and market skepticism about its business prospects beyond COVID vaccines.

Regulatory Shift Sparks Sell-Off Across Vaccine Stocks
 

Moderna’s stock fell 4.1% at the opening of regular trading in New York on Monday, with the company’s shares trading at $24.38, down $1.60 or 6.16% as of 10:28 AM EST. Other vaccine manufacturers also experienced declines, with BioNTech SE slipping 2.1%, Novavax Inc. falling 3.1%, and Vaxcyte Inc. declining 10%.

The market reaction followed an FDA memo from Vinay Prasad, a top agency official, who indicated that COVID shots played a role in the deaths of 10 children and announced that vaccine makers would need to perform additional tests to secure approvals.

The new FDA requirements will focus particularly on flu vaccines, demanding companies present more extensive data that can be both expensive and difficult to produce. The agency also plans to tighten rules around vaccines marketed to pregnant women and will require pneumonia shot makers to demonstrate that their vaccines actually reduce the disease.

These changes represent a significant shift in the regulatory landscape under Health and Human Services Secretary Robert F. Kennedy Jr., a longtime vaccine critic, whose administration has already limited COVID shot approvals to older people and those with underlying conditions.

More By This Author: