New Plague Vaccine Candidates Save 100% of Exposed Mice

Researchers have developed two vaccine candidates against the plague that protected 100% of mice in laboratory exposures, according to a report by Sciencepost published July 23, 2026. The development addresses a critical gap in public health, as no approved vaccine against the plague has existed to date.

The study focused on preventing infections caused by Yersinia pestis, the bacterium responsible for the plague. Sciencepost reports that these two candidates successfully prevented mortality in all mice exposed to the pathogen during the testing phase.

Plague Vaccine Development and Mouse Trial Results

The absence of a licensed vaccine has historically left medical professionals reliant on antibiotics to treat plague infections. According to Sciencepost, the two new candidates were tested for their ability to trigger an immune response capable of neutralizing the bacteria before it could cause fatal illness.

In the reported trials, every mouse that received the candidate vaccines survived exposure to the bacteria. This 100% survival rate in animal models serves as a primary indicator of the candidates’ potential efficacy in preventing the disease.

Public Health Context of Yersinia pestis

The plague is caused by the bacterium Yersinia pestis, which typically spreads to humans via flea bites or contact with infected animals. While the disease is rare in many parts of the world, it remains endemic in certain wildlife populations and can cause severe systemic infection if not treated promptly.

Current medical protocols for treating the plague rely on the administration of specific antibiotics. However, the development of a vaccine would provide a preventative layer of protection, particularly for individuals in high-risk regions or those handling infected animals.

Next Steps for Clinical Validation

The success in mouse models is a preliminary step in the vaccine development process. Sciencepost indicates that these results demonstrate the viability of the candidates, but further research is required to determine if the same level of protection translates to humans.

Standard medical research trajectories for new vaccines involve moving from animal models to human clinical trials to assess safety and efficacy. The researchers must now establish whether the immune response triggered in mice can be replicated in human subjects without adverse effects.