At least three doses need to be given during a 4-7 month time period before exposure to plague for the vaccine to be effective. Booster vaccines must be given every six months for eighteen months and then every 1-2 years for the vaccine to remain effective. Antibiotic treatment for those exposed to pneumonic plague is available but must be begun within 24 hours of the start of the symptoms to be effective. Streptomycin, tetracycline, and chloramphenicol used early are highly effective. Human to human transmission through the air is possible with pneumonic plague.
Rickettsial organisms are obligate intracellular parasites of humans.
Some that could be used in biological warfare are Coxiella bornetti which causes Q fever and a chronic endocarditis, and Rickettsia prowasecki , the causative agent of epidemic typhus. The two major toxins commonly associated with biological warfare are botulinum and Clostridium perfringens toxins. The botulinum toxin is extremely potent. It causes a respiratory paralysis and the victim suffers from asphyxia. Gas gangrene is the disease most commonly associated with Clostridium perfringens .