From COVID to pneumonic plague: mRNA vaccine scores another win with 100% effectiveness

In a major breakthrough, scientists from Tel Aviv University and the Israel Institute for Biological Research (IIBR) have created the world’s first mRNA-based vaccine to fight a deadly, antibiotic-resistant bacterium.

Just like the COVID-19 shots, this vaccine uses lipid nanoparticles to deliver protection—and get this—it showed 100% effectiveness in animal trials against pneumonic plague, one of the deadliest bacterial infections out there.


The research, which even landed the cover of Advanced Science journal, was led by Prof. Dan Peer and his team at Tel Aviv University, alongside scientists from IIBR. The star team includes Dr. Edo Kon, Dr. Inbal Hazan-HaLevy, and PhD student Shani Benarroch.

"Despite extensive global efforts over several decades to develop an effective and safe vaccine against Yersinia pestis, none has been approved to date in Western countries for protection against this notorious bacterial pathogen. This gap in protection is particularly concerning given that Y. pestis is classified as a Tier 1 biothreat agent due to its ability to cause plague – a severe and often fatal disease," the researchers have said.

What is Yersinia pestis?

Yersinia pestis might sound like the name of a villain from a sci-fi movie, but it's very real—and very deadly. This sneaky little bacterium is actually the cause of the infamous plague, including the Black Death that wiped out millions of people in Europe back in the 1300s. Yep, we're talking about that plague.

So, what exactly is Yersinia pestis? It’s a type of bacteria usually spread to humans through the bites of infected fleas, especially those hitching rides on rats. Once it gets into the body, it can cause a few different forms of illness—bubonic, septicemic, and pneumonic plague. Bubonic plague is the most common one and gets its name from the swollen, painful lymph nodes (called buboes) that show up, usually in the armpits, neck, or groin.

The scarier version, pneumonic plague, affects the lungs and can actually spread from person to person through coughing or sneezing. That’s part of what makes it so dangerous—it doesn’t need fleas to spread, just a human carrier with a bad cough. And if left untreated? It can be fatal in just a couple of days.

The wild part? Yersinia pestis is still around today, though in smaller, more contained outbreaks. Countries like the U.S., Madagascar, and the Democratic Republic of Congo still report occasional cases. The good news is that modern antibiotics can usually treat it—if caught early. Timing is everything with this bacteria.

What makes Yersinia pestis especially tricky is how fast it can overwhelm the immune system. It produces toxins and proteins that let it sneak past our defenses, making it hard for the body to fight back in time. And unfortunately, antibiotic resistance is becoming a concern, with some strains not responding to treatment like they used to.

That’s why the development of new vaccines—especially mRNA-based ones—is such a big deal. Scientists are working hard to stay a step ahead, and recent breakthroughs might finally give us better tools to fight back.

In short, Yersinia pestis is a tiny but terrifying bug with a brutal history and serious present-day potential. It may not be in the headlines every day, but it's definitely not one to ignore.