The Trump administration on Wednesday canceled a $766 million contract with Moderna, ending a major source of funding for efforts to develop a vaccine against flu viruses, including H5N1 bird flu.

The government first awarded Moderna the contract through the Biomedical Advanced Research and Development Authority, which allocates funds to address potential pandemic outbreaks. The money was awarded in July of 2024 and in January of 2025.

The U.S. Health and Human Services Department notified Moderna on Wednesday that it was withdrawing the funding.

“After a rigorous review, we concluded that continued investment in Moderna’s H5N1 mRNA vaccine was not scientifically or ethically justifiable,” HHS Communications Director Andrew Nixon said in a statement on Wednesday. “The reality is that mRNA technology remains under-tested, and we are not going to spend taxpayer dollars repeating the mistakes of the last administration, which concealed legitimate safety concerns from the public.”

"While the termination of funding from HHS adds uncertainty, we are pleased by the robust immune response and safety profile observed in this interim analysis of the Phase 1/2 study of our H5 avian flu vaccine and we will explore alternative paths forward for the program," said Moderna CEO Stéphane Bancel in a statement on the development. "These clinical data in pandemic influenza underscore the critical role mRNA technology has played as a countermeasure to emerging health threats."

RELATED STORY | CDC eliminates COVID-19 vaccine recommendations for children, pregnant women

The vaccine in testing was mRNA-based, like several of the successful COVID-19 vaccines deployed by Moderna and other companies.

Health Secretary Robert F. Kennedy Jr. has publicly questioned the efficacy of mRNA vaccines, including this week when he announced that the CDC would no longer recommend COVID vaccines for healthy children and healthy pregnant women. He cited a "lack of clinical data" supporting the need for repeat boosters.