The same technology that saved millions of lives during the COVID-19 pandemic appears to hold promise against another scourge of infectious disease, according to new research from the University of Pennsylvania.

Working with mice, hamsters and nonhuman primates, Penn researchers found that a modified version of the mRNA COVID-19 vaccine appeared to prevent and fight infections by Clostridioides difficile. This bacteria, also known as C. difficile or C. diff, causes half a million infections and kills roughly 30,000 people in the U.S. each year.

“C. diff is a really challenging pathogen,” said lead author Joseph Zackular, assistant professor of pathology and laboratory medicine at Penn. “This vaccine is kind of a really nice proof of principle” that the mRNA technology can tackle another major public health threat, he added.

C. diff hangs out in our gut, where it can produce toxins that cause problems such as diarrhea.

But it also exists as spores that live outside the body, which survive for long periods of time in soil or on surfaces, and serve as a major source of infections.

In a study published in November in the journal Science, Zackular and his team modified the mRNA vaccines that targeted the COVID-19 virus to instead attack all fronts of the C. diff bacteria. They found the vaccines that target C. diff cells and the toxins they produce generated a lasting immune response in mice and hamsters.

Researchers’ next steps include continuing to test the vaccine in animals and eventually humans.

As with any animal studies, there is no guarantee that what works in mice will also work in humans.