The Trump administration says it is pulling half a billion dollars from U.S. government-funded research projects to create new mRNA vaccines.

In a statement this week, U.S. Health Secretary Robert F. Kennedy Jr., a longtime vaccine critic, announced a "co-ordinated wind-down" amounting to the cancellation of $500 million worth of mRNA vaccine development under the Biomedical Advanced Research and Development Authority (BARDA). 

The technology itself was hailed as recently as the COVID-19 pandemic.

In 2023, the Nobel Prize in Physiology or Medicine was awarded to two scientists whose mRNA discoveries made it possible to create COVID-19 vaccinations. The committee credited mRNA technology with helping to save millions of lives, prevent severe COVID-19, reduce disease burden and enable societies worldwide to reopen.

The loss of research funding has dismayed infectious disease experts who note that mRNA technology allows faster production of shots than older vaccine-production methods, buying precious time if another pandemic virus were to emerge.

Here's how medical experts in Canada and the U.S. are reacting to the funding cut and what they say it could mean.

WATCH | The U.S. is ending mRNA vaccine funding: 

The U.S. just killed mRNA vaccine funding — what now?

U.S. Health Secretary Robert F. Kennedy Jr. has cancelled $500 million in funding for the development of mNRA vaccine technology. For The National, CBC’s Heather Hiscox asks infectious disease specialist Dr. Allison McGeer and health researcher Bradley Wouters to break down what kind of impact this could have on fighting disease in Canada and around the world.

What is mRNA vaccine technology and why is it exciting?

Vaccines train our immune system to respond to pathogens. Traditionally, vaccines have used inactive or weakened versions of a pathogen that isn't enough to make a person ill, but does kickstart the body's immune response.

Messenger RNA (mRNA), discovered in 1961, is a natural molecule that serves as a recipe for the production of proteins in the body.

In mRNA vaccines, the approach starts with a snippet of genetic code that carries instructions for making proteins.

Scientists pick the protein to target, inject that blueprint into the body's cells, which then make just enough of the proteins to trigger an immune response — essentially producing its own vaccine dose.

Scientists are mainly excited about the speed with which mRNA vaccines can get protection into arms.

Michael Osterholm, an expert on pandemic preparation with the University of Minnesota, says using older vaccine technology to target a pandemic flu strain would take 18 months to make enough doses to vaccinate only about one-fourth of the world.

He says using mRNA technology to make a flu vaccine could change that timeline dramatically. "By the end of the first year, we could vaccinate the world."

Besides the advantage of how quickly mRNA vaccines can be made, Dr. Allison McGeer, an infectious diseases specialist in Toronto, says they're also easier to standardize.

"It has a whole lot of other flexibilities that if you know it works, makes it a really exciting addition" to older technologies used to make vaccines. 

What mRNA vaccine research is going on now?

Beyond COVID vaccines, mRNA vaccine technology is in a Health Canada approved vaccine for respiratory syncytial virus (RSV). An mRNA vaccine for influenza has also reached Phase 3 clinical trial, the last step before manufacturers submit to regulators to release a vaccine to market.

There have also been more than 100 clinical trials to assess the potential of mRNA vaccine technology to treat various cancers including lung, breast, prostate, melanoma and, more recently, pancreatic cancer.

Dr. Peter Hotez, a professor of pediatrics and molecular virology at Baylor College of Medicine in Houston, says there's concern that cancelling funding for mRNA vaccine research will have negative consequences for research on other diseases. 

"The mRNA technology is looking really exciting for next-generation cancer immunotherapeutics," said Hotez, who also works at Texas Children's Hospital Center for Vaccine Development.

"So will this throw cold water on a whole big effort that we're pursuing as well to develop next-generation cancer vaccine? That's an unknown question."

Other research teams are testing potential mRNA-based vaccines to fight HIV and to treat autoimmune diseases. These are in early stage clinical trials or animal-stage studies. 

Could other countries pick up the slack?

Though there are other countries working on mRNA vaccine technology, Hotez called the U.S. the single largest vaccine market. 

He says the announcement that funding was being cut could dissuade pharmaceutical companies from pursuing the vaccine technology if they believe it won't sell there.

He says it's unclear whether other industrialized countries could pool their support to make up the $500 million US cut.

Are there safety issues with mRNA vaccines as RFK Jr. suggested?

In a video on the social media platform X, Kennedy claimed that mRNA vaccines were unsafe and ineffective.

He said that after reviewing the science and consulting top U.S. experts, the department of Health and Human Services (HHS) "has determined that mRNA technology poses more risk than benefits against these respiratory viruses." 

In the video, Kennedy also claimed that mRNA vaccines "paradoxically encourage new mutations and can actually prolong pandemics as the virus constantly mutates to escape the protective effects of the vaccine."

Angela Rasmussen, a virologist at the University of Saskatchewan, says Kennedy is wrong about what prolongs pandemics. 

WATCH | What RFK Jr. gets wrong on mRNA vaccines:

Fact checking RFK Jr. on mRNA vaccines

U.S. Health Secretary Robert F. Kennedy Jr., a longtime vaccine critic, claimed this week that mRNA vaccines can prolong pandemics. Angela Rasmussen, a virologist at the University of Saskatchewan, explains why mRNA vaccines actually help to shorten pandemics.

"Viruses mutate when they replicate, and they replicate when they spread through a population of people," Rasmussen said.

"The best way to prevent a virus from spreading through a population of people is to make sure those people are protected against the virus by vaccination."

In a news release on Tuesday, Kennedy also referred to COVID and flu as upper respiratory infections, which Hotez notes is incorrect. 

Unlike the common cold, he says, COVID-19 and influenza are lower respiratory tract infections with significant cardiovascular and other health effects.

"That's part of the disinformation machine … to downplay the severity of these illnesses," said Hotez. 

Will lack of funding hurt access to existing flu vaccines?

Rasmussen says influenza vaccines won't be affected in the U.S. as they're manufactured using the inactivated virus method, not mRNA. 

In the video posted to social media, Kennedy said the U.S. supports "safe, effective vaccines for every American who wants them."

But many infectious disease experts have noted that mRNA vaccines themselves are also safe and effective.  

"The mRNA technology has been proven to be highly effective," Hotez said. "By some estimates, 3.2 million American lives were saved by COVID mRNA vaccines during the pandemic."