The U.S. Department of Health and Human Services (HHS) has abruptly canceled a contract worth more than $590 million with Moderna, ending federal support for the company’s efforts to develop a messenger RNA (mRNA) vaccine against bird flu and other pandemic-prone influenza strains.

The canceled agreement, initially established under the Biden administration, was intended to accelerate the development and potential stockpiling of Moderna’s mRNA-based H5N1 avian influenza vaccine. The funding aimed to support late-stage clinical trials and expand readiness for a possible bird flu pandemic, as the H5N1 strain continued to devastate poultry and had begun infecting other species, including cattle and humans.

The Trump administration’s decision also relinquished the government’s right to purchase doses in advance of a pandemic, a safeguard previously built into the contract.

HHS officials cited ongoing concerns about the safety and maturity of mRNA technology as the primary reason for terminating the contract. In a statement, HHS Communications Director Andrew Nixon said, “After a rigorous review, we concluded that continued investment in Moderna’s H5N1 mRNA vaccine was not scientifically or ethically justifiable.” Nixon also emphasized that the agency did not want to repeat what it described as “mistakes made during COVID-19 vaccine efforts,” and labeled mRNA technology as “under-tested” for this application.

Those vaccine efforts happened under the first Trump administration in 2020.

The concept of using messenger RNA (mRNA) as a therapeutic tool dates back to the early 1990s, with foundational research carried out at the University of Wisconsin and later at the University of Pennsylvania. Early experiments demonstrated that mRNA could instruct cells to produce specific proteins, but the technology faced significant hurdles, particularly the instability of mRNA outside cells and the immune system’s tendency to attack foreign RNA.

A major advance came in 2005, when Dr. Katalin Karikó and Dr. Drew Weissman discovered that modifying nucleosides in mRNA could prevent unwanted immune reactions, making the technology viable for vaccines and therapeutics. This innovation was crucial for both Moderna and BioNTech, the companies that would later develop the first mRNA COVID-19 vaccines..

While the U.S. government invested heavily in mRNA research over several decades, the technology also benefited from international collaboration. BioNTech, founded in Germany by Dr. Uğur Şahin and Dr. Özlem Türeci, became a key player after bringing Karikó on board in 2013. Both BioNTech and Moderna licensed patents based on the Karikó-Weissman discoveries.

Although mRNA vaccines had been in development for cancer and infectious diseases since the 2000s, their breakthrough moment came with the COVID-19 pandemic. The Pfizer-BioNTech and Moderna vaccines were authorized for emergency use in December 2020, after clinical trials involving tens of thousands of participants demonstrated over 90% efficacy in preventing symptomatic COVID-19. These vaccines have since been credited with saving millions of lives worldwide.

With concern of an H5N1 avian influenza pandemic, Moderna had already launched a Phase 1/2 clinical trial of its H5N1 vaccine, reporting promising interim results. According to the company, nearly 98% of participants developed protective antibody levels three weeks after receiving two doses, and the vaccine demonstrated a robust safety profile.

Although avian flu spreads rapidly among wild birds and cattle, there have also been several documented human infections. According to the World Health Organization, between 2003 and February 2025, there have been 972 confirmed human cases of H5N1 influenza, resulting in 468 deaths.

With the loss of federal funding, Moderna’s bird flu vaccine program faces significant uncertainty. The company will need to seek alternative funding sources or partnerships to continue late-stage development and potential manufacturing.

Such contract cancellations could make pharmaceutical companies hesitant to engage in future business with the United States.

“Unless there is a clear reason for terminating the funding, not only will we be left less prepared, potentially risking the lives of millions, but vaccine and other innovators will question the reliability of U.S. government investments and partnerships, and may think twice about engaging in public health efforts for which there is no clear reward in terms of a marketed product,” Former FDA chief scientist Dr. Jesse Goodman said.