Health Secretary Robert F. Kennedy Jr. has canceled nearly $500 million of grants and contracts for developing mRNA vaccines, the Department of Health and Human Services announced on Tuesday.
It is the latest blow to research on this technology. In May, the Department of Health and Human Services revoked a nearly $600 million contract to the drugmaker Moderna to develop a vaccine against bird flu.
The new cancellations dismayed scientists, many of whom regard mRNA shots as the best option for protecting Americans in a pandemic.
“This is a bad day for science,” said Scott Hensley, an immunologist at the University of Pennsylvania who has been working to develop an mRNA vaccine against influenza.
The health department said in its release that the cancellations affected 22 projects managed by the Biomedical Advanced Research and Development Authority, or BARDA.
With this move, the department is “undermining our ability to rapidly counter future biological threats,” said Rick Bright, a flu expert who was ousted as chief of BARDA during the first Trump administration and resigned from a lesser position in protest.
“We’re weakening our frontline defense against fast‑moving pathogens — a huge strategic failure that will be measured in lives lost during times of crisis,” he added.
Chris Meekins, an assistant secretary for pandemic preparedness in the first Trump administration, said that ending BARDA’s mRNA work created a “national security vulnerability.”
“These tools serve as a deterrent to prevent other nations from using certain biological agents,” Mr. Meekins said in an email and on social media. “The speed of the technology to create new biodefense capabilities is a national security asset.”
First used during the Covid-19 pandemic by Pfizer-BioNTech and Moderna, mRNA shots instruct the body to produce a fragment of a virus, which then sets off the body’s immune response.
Unlike traditional vaccines, which can take years to develop and test, mRNA shots can be made within months and quickly altered as the virus changes.
Mr. Kennedy has been sharply critical of the technology. In a video posted on social media on Tuesday, he claimed incorrectly that mRNA vaccines do not protect against respiratory illnesses like Covid and the flu, that they drive viruses to evolve and that a single mutation in a virus renders the vaccine ineffective.
“As the pandemic showed us, mRNA vaccines don’t perform well against viruses that infect the upper respiratory tract,” he says in the video.
“By issuing this wildly incorrect statement, the secretary is demonstrating his commitment to his long-held goal of sowing doubts about all vaccines,” said Jennifer Nuzzo, director of the Pandemic Center at the Brown University School of Public Health.
“Had we not used these lifesaving mRNA vaccines to protect against severe illness, we would have had millions of more Covid deaths,” she said.
The health department said it will favor other types of shots over those using mRNA, like whole-cell vaccines. That technology is more than 100 years old. The United States has not used a whole-cell vaccine for whooping cough since the 1990s because it was potent but harsh, often setting off high fevers and seizures.
Mr. Kennedy himself assailed the leading international vaccine organization, Gavi, the Vaccine Alliance, for continuing to use the whole-cell vaccine in low-income countries, citing it as the reason the United States was pulling funding from the organization.