A new plague vaccine has shown 100% efficacy in mice.

A new vaccine against plague has shown 100% efficacy in mice, according to research published in Science Translational Medicine. The study, conducted by scientists at the Department of Medicine at the University of Texas Medical Branch in Galveston, developed two novel vaccines, LMA and LMP, that demonstrated complete protection against Yersinia pestis, the bacterium responsible for plague. In trials involving mice, all vaccinated animals survived exposure to lethal doses of the bacteria, while none of the control group mice lived beyond four days after infection. The researchers tested the vaccines using a strategy known as “prime-pull,” which involves administering two distinct types of inoculations. The first dose was delivered via intramuscular injection, designed to prime the immune system. The second dose was either a repeat injection of the same vaccine or a nasal spray based on an adenovirus vector, intended to pull immune cells toward the site of potential pathogen entry, in this case, the nasal mucosa. This dual approach aimed to enhance both the speed and strength of the immune response. Plague, though often associated with historical pandemics such as the Black Death, remains a modern health threat. Each year, hundreds to thousands of cases are recorded globally, primarily in Africa, although outbreaks can occur almost anywhere humans live near fleas that carry Y. pestis. While bubonic plague, the most common form, characterized by swollen lymph nodes, is treatable with antibiotics if detected early, pneumonic plague, a far more dangerous variant that affects the lungs, is nearly always fatal if treatment is delayed beyond three to four days after symptoms appear. Antibiotic resistance among Y. pestis strains further complicates treatment options. The newly developed vaccines target all forms of plague, including the highly lethal pneumonic strain. In tests, mice receiving the vaccines were fully protected even when exposed to extremely high bacterial loads. However, one group showed slightly reduced protection—80% instead of 100%. These mice had received two intramuscular doses of either LMA or LMP but not the nasal spray. Additionally, they were genetically modified to lack the gene for producing interferon-gamma, an essential immune molecule that plays a key role in defending against bacterial infections. Analysis of serum and mucus samples from vaccinated mice revealed a robust antibody response, suggesting the vaccines effectively stimulated immunity. Researchers emphasized that while these results are promising, further evaluation is needed. They plan to test the vaccines in primates before moving forward with human clinical trials. The team also highlighted the importance of assessing how combined vaccines might induce rapid and effective immunity for emergency use, as well as their ability to provide long-term protection. The absence of an approved plague vaccine in the United States underscores the urgency of such research. The U.S. Food and Drug Administration (FDA) currently does not license any vaccine for plague, and the World Health Organization recommends vaccination only for high-risk groups, such as healthcare workers in affected areas. With growing concerns over antibiotic resistance and the potential for resurgence of plague outbreaks, the development of safe and effective vaccines could play a crucial role in global public health preparedness.