Is there a vaccine against plague?
Plague is rare and can be treated with antibiotics. So why are researchers trying to develop better plague vaccines?
- 8 October 2026
- 4 min read
- by Linda Geddes
At a glance
- Vaccines against plague have existed for more than 100 years, although none are currently widely available.
- While vaccines based on killed plague bacteria were licensed for use in some countries, these offered limited protection against pneumonic plague and could cause significant side-effects. Vaccines based on weakened bacteria are also used in some countries, but reliable estimates of their effectiveness are lacking.
Researchers are developing new vaccines against both bubonic and pneumonic plague, driven by concerns about protecting those without access to rapid treatment, as well as antibiotic resistance and potential bioterrorism threats.
Reports of a possible case of pneumonic plague in a Russian laboratory worker have raised questions about how people can be protected against a disease that has terrorised humanity for centuries.
WHO has identified the development of safer, more effective plague vaccines as a priority, particularly ones capable of protecting against bubonic and pneumonic plague.
Although plague is now relatively rare, it still causes hundreds of infections each year, mostly in parts of Africa. It can be successfully treated with antibiotics, but prompt diagnosis and treatment are essential. This is particularly true of pneumonic plague, which affects the lungs and can spread between people through respiratory droplets. Without treatment, it can be fatal within 24 hours of symptoms appearing.
While vaccines against plague have existed for more than a century, their effectiveness against pneumonic plague has been less certain than against bubonic plague: the form most commonly associated with the Black Death, which is usually transmitted through the bites of infected fleas.
The need to protect people in places where rapid treatment isn’t guaranteed, concerns about antibiotic-resistant strains (which have already been identified in Peru and Madagascar) and the potential use of plague bacteria as a biological weapon are all driving efforts to develop better vaccines. So, what vaccines are available today, and what could future plague vaccines offer?
How common is plague?
Plague is caused by the bacterium Yersinia pestis, which circulates in wild rodents and their fleas in many parts of the world. Humans usually become infected through the bites of these fleas, although the disease can also be transmitted through contact with infected animals or, in the case of pneumonic plague, through respiratory droplets from an infected person. There have also been isolated cases of laboratory-acquired plague, with the greatest concern being accidental inhalation of bacteria, which could happen if a sample spilled or was handled without adequate safety precautions.
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According to the World Health Organization (WHO), there were 3,847 suspected cases of human plague and 423 deaths reported worldwide between 2019 and 2025. Most cases occurred in the Democratic Republic of the Congo and Madagascar, where the disease continues to circulate in wild rodents and their fleas.
In Madagascar, a 2017 outbreak of plague resulted in 2,348 confirmed, probable or suspected cases, and 202 deaths. Of these cases, 1,791 (76%) were classified as pneumonic plague.
Are there vaccines against plague?
Vaccines against plague have existed since the late 19th century, although none are currently widely available. The earliest, developed by a scientist called Waldemar Haffkine in India in 1897, contained whole Y. pestis bacteria that had been killed by heat. Millions of doses were administered in the decades that followed, helping to reduce the impact of plague outbreaks in India.
Other vaccines containing killed bacteria followed, including one licensed in the US that was used to protect people at increased risk of plague, such as military personnel and laboratory workers. Although these appeared to offer some protection against bubonic plague, they were less effective against pneumonic plague and could cause unpleasant side-effects. Production of the US vaccine ended in 1999, while a similar vaccine remained licensed in Australia until 2005.
China and Russia have pursued an alternative approach, developing vaccines containing live but weakened Y. pestis bacteria. These have been licensed and used for decades, particularly among people at increased risk of exposure to plague.
Although there is some evidence to suggest that these ‘live’ vaccines can help protect against bubonic plague, and possibly pneumonic plague, findings have been mixed, and reliable estimates of their effectiveness are lacking. Also, because the weakened bacteria can still cause disease under some circumstances, there are safety concerns about their use in people with certain underlying health conditions.
Are better plague vaccines on the horizon?
WHO has identified the development of safer, more effective plague vaccines as a priority, particularly ones capable of protecting against bubonic and pneumonic plague. In 2018, it published a report outlining the characteristics future plague vaccines would need if they were to be used during outbreaks, or to protect people at particularly high risk of plague, either because of their profession or because they live in areas where plague is endemic.
Several approaches are being investigated, including vaccines made from purified Y. pestis proteins or new strains of weakened bacteria, as well as candidates that use harmless bacteria or viruses to deliver genetic instructions for plague proteins, or use DNA or mRNA to instruct the body to produce these proteins and trigger an immune response. Although some candidates have progressed to human trials, none of these newer vaccines has yet been approved for routine use.
