Vaccines May Vanquish The Plague, Finally

The plague is best known for causing the Black Death pandemic of the 14th century. But the risk of the plague spreading remains a real health issue today.

Scientists in Texas are developing a vaccine to protect humans from the plague’s potential impact.

Dr. Ashok Chopra and other researchers at the University of Texas Medical Branch at Galveston published a study of the three newest plague vaccine candidates.

“So far, it looks very promising, at least in the two animal models we have tested,” said Chopra, a professor of microbiology and immunology.

The plague is an infectious fever caused by the bacillus Yersinia pestis, a bacterium transmitted from rodents to humans by the bite of infected fleas. The plague persists in some parts of the world where large populations of rodents harbour the fleas and occasionally pass them to humans.

The impetus for his work was the anthrax attacks of 2001, when letters containing anthrax were mailed to media outlets and congressional offices. Congress required the departments of Health and Human Services and Agriculture to regulate certain biological agents and toxins that could pose a severe threat to public health.

“There has been a history of using or developing plague as a bioterrorism agent,” said Dr. Paul Mead, a medical epidemiologist with the Centers for Disease Control and Prevention (CDC).

There are three types of plague infection — bubonic, septicemic and pneumonic — and all are caused by the Yersinia pestis bacteria.

Left untreated, the bubonic form has a 40 percent to 70 percent mortality rate, and pneumonic and septicemic plague are virtually always fatal.

According to the World Health Organization, there were 783 cases of the plague reported worldwide in 2013, including 126 deaths. The three most endemic countries are Madagascar, the Democratic Republic of Congo and Peru.

According to the CDC, in the USA, as of early November 2016, only four cases had been reported and all patients recovered.

Vaccines for the plague do already exist, but they have some serious flaws.

Dr. Chopra’s experimental vaccines protect against the pneumonic plague and don’t cause side effects. These researchers deleted genes in each candidate strain in order to weaken, but not kill the bacteria.

Chopra also has a different type of plague vaccine in the works which involves the bacteria’s antigens. It’s been tested in non-human primates and is shown to be “highly protective.”

“Everybody’s immune system is different so some people could be protected and some may not be,” Dr. Chopra said. “Our goal is to do parallel studies so that we have in our pipeline several vaccine candidates.”

Bethany L Tiner, Jian Sha, Yingzi Cong, Michelle L Kirtley, Jourdan A Andersson, Ashok K Chopra were inolved in this study.

No conflicts of interest were disclosed.