Washington DC - President Donald Trump's administration on Tuesday announced it would terminate 22 federal contracts for mRNA-based vaccines, questioning the safety of a technology credited with helping end the Covid pandemic and saving millions of lives.

The announcement, made by Health Secretary Robert F. Kennedy Jr., marks his latest effort to weave vaccine skepticism into the core of US government policy.

"We reviewed the science, listened to the experts, and acted," Kennedy said in a statement.

The Health Department's Biomedical Advanced Research and Development Authority (BARDA) is "terminating 22 mRNA vaccine development investments because the data show these vaccines fail to protect effectively against upper respiratory infections like COVID and flu," he added.

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"We're shifting that funding toward safer, broader vaccine platforms that remain effective even as viruses mutate."

The changes affect Moderna's mRNA bird flu vaccine – a move the company itself disclosed in May – as well as numerous other programs, including "rejection or cancellation of multiple pre-award solicitations" from pharmaceutical giants Pfizer and Sanofi.

In total, the affected projects are worth "nearly $500 million," the Department of Health and Human Services (HHS) said. Certain late-stage projects were excluded from the move "to preserve prior taxpayer investment."

"Let me be absolutely clear: HHS supports safe, effective vaccines for every American who wants them," Secretary Kennedy said.

"That's why we're moving beyond the limitations of mRNA and investing in better solutions."

Since taking office, Kennedy, who spent two decades sowing misinformation around immunization, has overseen a major overhaul of US health policy – firing, for example, a panel of vaccine experts that advise the government and replacing them with his own appointees.

In its first meeting, the new panel promptly voted to ban a longstanding vaccine preservative targeted by the anti-vaccine movement, despite its strong safety record.

He has also ordered a sweeping new study on the long-debunked link between vaccines and autism.

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Unlike traditional vaccines, which often use weakened or inactivated forms of the target virus or bacteria, mRNA shots deliver genetic instructions into the host's cells, prompting them to produce a harmless decoy of the pathogen and train the immune system to fight the real thing.

Though in development for decades, mRNA vaccines were propelled from lab benches to widespread use through President Trump's Operation Warp Speed – a public-private partnership led by BARDA that poured billions into companies to accelerate development.

The technology's pioneers, Katalin Kariko and Drew Weissman, were awarded the 2023 Nobel Prize in Medicine for their work contributing "to the unprecedented rate of vaccine development during one of the greatest threats to human health in modern times."