After decades of stalled progress, researchers say a long-running effort to build a vaccine against a major cause of severe diarrheal illness has hit a new milestone.

Scientists developed a technology targeting enterotoxigenic Escherichia coli, or ETEC, a bacterium responsible for millions of diarrheal illnesses each year. The technology has now been licensed to French vaccine manufacturer Valneva for further development.

The findings follow decades of research led by scientists at the University of Bergen and the Norwegian Research Center, NORCE.

ETEC is one of the most common bacterial causes of severe diarrhea worldwide and disproportionately affects children in low- and middle-income countries. Despite years of research, there is currently no broadly effective vaccine to prevent the infection, according to the study.

Researchers focused on a toxin produced by ETEC that has long been considered one of the biggest obstacles to vaccine development.

James Fleckenstein, a professor of medicine and molecular microbiology at the Washington University School of Medicine in St. Louis, said the findings mark a promising step.

“We still have a lot of work to do to translate these findings to an actual vaccine,” Fleckenstein, who was not involved in the research, told Fox News Digital.

“But the approach does look promising in the sense that the proteins elicit strong antibody responses that appear to offer protection against diarrheal illness after the first infection in children in developing countries.”

Researchers said that if the vaccine eventually reaches patients, it could help protect children against some of the most severe forms of diarrheal disease caused by ETEC.

Fleckenstein said travelers can reduce their risk of diarrheal illnesses by avoiding high-risk foods, including meals from street vendors in areas where sanitation may be poor, drinking bottled water in higher-risk regions, and practicing good hand hygiene.

He also said vaccines are available to protect against typhoid fever and that travelers should consult their physician before traveling internationally.

The researchers said the work has limitations. The technology is still in development and has not yet been tested as an approved vaccine among the public.

Under the licensing agreement, Valneva can continue advancing the research, but the vaccine would still need additional laboratory studies, clinical trials and regulatory review before it becomes available.

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