WASHINGTON, D.C. – The U.S. Department of Health and Human Services announced on Tuesday it would cancel $500 million worth of vaccine development projects.

The announcement has scientists and experts split over the benefits of messenger RNA vaccine development.

Messenger RNA vaccines work by delivering a small piece of genetic code that instructs cells to produce a harmless viral protein. This protein triggers an immune response, teaching the immune system to recognize and fight the actual virus if the body is later exposed to it.

“The data show that these vaccines fail to protect effectively against upper respiratory infections like COVID and flu,” said HHS Secretary Robert F. Kennedy Jr.

The department is canceling 22 projects including awards to Moderna for bird flu vaccine development, contracts with Emory University and rejecting proposals from Pfizer and Sanofi. The department is also restructuring contracts with companies like AstraZeneca and scaling back work in existing contracts with Luminary Labs.

“We’re shifting that funding toward safer, broader vaccine platforms that remain effective even as vaccines mutate,” Kennedy said.

Deborah Dunn-Walters, an immunology professor at the University of Surry, said Kennedy’s claims of mRNA vaccines causing increased mutation rates in flu and COVID-19 are false.

“Mutation is a natural process that occurs with these viruses, and the use of any vaccine does not impact it,” Dunn-Walters said.

Robert Malone, a physician and biochemist who was involved in early research with mRNA vaccines, praised the announcement.

“This is a historic moment, the likes of which I never expected to see,” Malone said. “The Secretary and his team are really making a big difference on both smaller as well as the big issues.”

Katalin Kariko, a University of Pennsylvania biochemist, said Kennedy is “misinformed” in his assessment of mRNA vaccine efficacy.

“When you just reject and rely on misinformation then you make a decision like he made which is false,” Kariko said.

She said she is worried about how the next generation of scientists and public health leaders will respond to the changes made by the Trump administration. She said many scientists might move away from the United States because of its shifting priorities in health research funding.

In May, Kennedy announced HHS would cut a $590 million contract with Moderna to develop a vaccine that would protect against bird flu.