The Plague Remains Alive Today

The Plague is a centuries-old disease that can still be deadly today. Vaccine researchers are developing new products that could protect people against a plague infection.

Humans usually get the plague after being bitten by a rodent flea that is carrying the plague bacterium or by handling an animal infected with plague. The plague can take different clinical forms, but the most common are bubonic, pneumonic, and septicemic.

In this new study, researchers tested three vaccines that were designed to protect people from the bacteria that causes the plague, known as Yersinia pestis.

Specifically, these vaccine candidates were designed to protect people against the bacteria that cause pneumonic plague, the only type that spreads through airborne transmission.

"It is crucial that a potential vaccine candidate … [against plague] demonstrates long-term immune responses and protection," the researchers wrote in the Oct. 13 issue of Vaccines. This new study showed that all three vaccines stimulated an immune response that was capable of protecting animals from developing a pneumonic plague infection.

Although vaccines against plague have been developed in the past, there is currently no plague vaccine approved by the U.S. Food and Drug Administration (FDA).

There was previously a FDA approved vaccine that protected humans against bubonic plague, but it did not prevent pneumonic plague and its production was discontinued.

Plague is best known for killing millions of people in Europe, in a pandemic called the Black Death. The Black Death was an epidemic outbreak of bubonic plague in Europe around 1348 that killed between one-third of the population in less than five years. The epidemic spanned from China to England to North Africa, transmitted to people along trade routes.

Plague patients develop symptoms which include the sudden onset of fever, headache, chills, and weakness and one or more swollen, tender and painful lymph nodes.

An average of seven human plague cases are reported annually in the western United States, but significantly more cases occur in Africa and Asia, according to the Centers for Disease Control and Prevention (CDC).

"The optimal strategy for protecting people … against this deadly disease would be through vaccination," Ashok Chopra, a professor of microbiology and immunology at The University of Texas Medical Branch at Galveston, said in a statement.

These researchers plan to continue testing the effectiveness of these plague vaccines before they are used in people.