Health and Human Services Secretary Robert F. Kennedy Jr. this week defunded research in messenger RNA vaccines, which could create a chilling effect that could jeopardize efforts to develop vaccines against breast cancer, experts said.

The government is cancelling almost $500 million in 22 research contracts previously granted through the Biomedical Advanced Research and Development Authority, a subsidiary of HHS. In addition, HHS will not initiate new grants for projects involving messenger RNA, the revolutionary basis for COVID-19 immunizations. The scientists who helped discover mRNA technology won the 2023 Nobel Prize for Medicine; no vaccine has ever been so quickly developed and produced as the COVID-19 vaccines.

Kennedy, who is known for his broad opposition to vaccines, said HHS is terminating the contracts because “these vaccines fail to protect effectively against upper respiratory infections” — despite the broad medical consensus, backed by large studies, which holds that the mRNA-based COVID-19 vaccines are safe and effective.

The government’s move has been widely decried by vaccine researchers, immunologists and public health experts. Some scientists have touted mRNA technology as a possible avenue to develop other vaccines, including ones to treat various cancers, including breast cancer, which is the most commonly diagnosed cancer worldwide.

Cancer vaccines have been a rapid area of growth for medical research in recent years. Prophylactic vaccines, such as the human papillovirus vaccine, prevent cancers. But immunologists and cancer researchers have been working to develop new therapeutic vaccines — products that can trigger the immune system to fight against cancer cells after they have already developed, working instead as a treatment. There is a growing consensus that mRNA vaccines could be particularly effective in fighting cancers. 

Most cancer vaccines currently in clinical trials are not based on mRNA. But it’s an area of growing interest: More than 120 clinical trials have been registered with the federal government to explore how mRNA vaccines could treat different cancers. Vaccines in development that make use of mRNA include those that could treat melanoma, lymphoma and colorectal cancer; scientists are also examining the possibility to treat pancreatic, lung and breast cancer.

The 22 contracts terminated were for treatments and vaccines for conditions such as influenza, COVID-19 and bird flu, not cancer. In its announcement, HHS said “other uses of mRNA technology” beyond prophylactic vaccines will not be affected. 

But some cancer researchers still fear that Kennedy’s promise will cast a chill upon a promising line of inquiry, slowing progress and possibly preventing scientists from developing effective cancer treatments.

“There’s no question that the U.S. federal government has been one of the largest funders of biomedical research and innovation in the world,” said Dr. Herbert Kim Lyerly, an immunologist at Duke University. 

Lyerly is part of a team currently working on a clinical trial for an RNA vaccine that could treat many common cancers, including breast cancer. So far, he said, the results have been promising. His work is government-supported but wasn’t affected by the recent cancellation of mRNA contracts. 

Still, he believes the shift in policy could deter scientific innovation — if researchers can’t count on stable funding to explore mRNA-based options, it could prevent them from developing the most effective therapeutics.

“It reduces the options you have to explore strategies to reduce the burden of disease, to prevent disease, to improve the quality of life of people in this country,” he said. “To take away any of the tools to potentially have an impact is likely to limit progress.”

Others have echoed his concerns, including a spokesperson for the Biotechnology Innovation Center, who told the news organization STAT that scaling back government investments in mRNA vaccines “could erode progress and discourage investment in other promising areas of research, including cancer and rare diseases.” In a statement on the social media platform X, former surgeon general Jerome Adams, who served in President Donald Trump’s first term, called the move “dangerous,” highlighting its implications for flu, RSV, HIV, Zika, autoimmune diseases and cancer.

Still, some researchers said they anticipate that any vacuum created by the federal government’s retreat will be filled by other entities: foundations and nonprofits that focus on cancer. 

“People are committed to mRNA because it has been shown to be safe and effective. People will still continue to do that research,” said Dr. Alison Stopeck, an oncologist at Stony Brook Cancer Center who focuses on breast cancer. 

If the federal government does not support this kind of work, she added, “Foundations and donors will step in and provide some resources for this as well — because donors and foundations know how important this research is.”

Already, medical researchers have been left reeling after the federal government’s cancellation of major funding through institutions such as the National Institutes of Health — a move the nonpartisan Government Accountability Office recently deemed illegal. That’s been compounded by other funding cuts to individual research universities as well as a broader federal effort to curb funding into medical research that considers gender or gender inequality.

Though deaths from cancers have been declining, an April report from the National Cancer Institute found that the incidence of cancer actually increased for women over the past two decades. Breast cancer is also growing more common, particularly among young women and Asian American and Pacific Islander women. Black women who are diagnosed with breast cancer are substantially more likely to die than White women.