Patient description: The patient is a 35-year-old woman with myasthenia gravis, class IIa. She complains of diplopia and fatigue and weakness that affects mainly her upper limbs. She had a positive anti-AChR antibody test, and her single fiber electromyography (SFEMG) was positive. She takes pyridostigmine 60 mg three times a day. But she still has some symptoms that interfere with her job. She is a research coordinator and has 3 children. Her 70-year-old father has hypertension. She does not smoke or use illicit drugs. She drinks alcohol occasionally at social events. Her physical exam and lab studies were not remarkable for any other abnormalities. BP: 110/75 Hgb: 11 g/dl WBC: 8000 /mm3 Plt: 300000 /ml Creatinine: 0.5 mg/dl BUN: 10 mg/dl Beta hcg: negative for pregnancy

Clinical trial eligibility criteria: eligible ages (years): 18.0-40.0,  Pneumonic Plague Preventive Therapy The volunteer is male or female and 18 to 40 years of age (inclusive) at the time of the first dose of investigational product Good health as determined by screening medical history and physical examination The volunteer has the following laboratory parameters within normal range: total WBC, Hemoglobin, platelets, LFT (AST, ALT, ALP, Bilirubin) and/or ≤ 1+ proteinuria. Other laboratory parameters must be within 10 % of the upper or lower limits of the normal range of the University of Kentucky clinical laboratory and not clinically significant as assessed by the Investigator and/or Sponsor Medical Monitor The volunteer has a normal electrocardiogram (ECG). However, if a potential volunteer is reported to have a benign ECG abnormality (e.g., sinus bradycardia) the results may be discussed with the Sponsor Medical Monitor and Covalent Medical Monitor. With the agreement of the Investigator, Covalent Medical Monitor and Sponsor Medical Monitor and documentation of the consultation in the volunteer's study record the Investigator may the volunteer in the study The volunteer is willing to have his or her blood samples stored for future plague research studies The volunteer has signed the Informed Consent Form, successfully completed (at least 90 % correct) the Test of Understanding, and has signed the HIPAA authorization form The volunteer agrees not to donate blood for at least 30 days following vaccination The volunteer is willing to comply with the requirements of the protocol through the post-vaccination Day 180 (± 7 days) visit Female volunteers must be of non-childbearing potential (i.e., surgically sterilized or postmenopausal), or must not be pregnant (as indicated by a negative serum pregnancy test within 24 hours prior to rF1V administration) or nursing, and must use two types of an acceptable form of FDA-approved contraception (barrier method, Depo-Provera, Norplant, Ortho Evra (birth control patch), oral contraceptives) through 30 days after the second (final) vaccination of rF1V (i.e. Day 58). If abstinent, two forms of birth control are not required (Cohort 4 Extension) The volunteer must be an active participant enrolled in Phase 1 rF1V-01 protocol - Cohort 4 (160 ug) completing day 180 procedures as defined in rF1V-01 protocol  Have a history of plague disease or have received any plague vaccine Have active tuberculosis or other systemic infectious process by review of systems and physical examination Have a history of allergy to kanamycin or aminoglycosides Positive for human immunodeficiency virus (HIV); hepatitis C virus (HCV) or hepatitis B surface antigen (HbsAg) Have a history of immunodeficiency, chronic illness requiring continuous or frequent medical intervention, acute/chronic untreated conditions, autoimmune disease, or use of immunosuppressive medications The volunteer has chronic, severe or recurrent joint pain or arthritis of any etiology The volunteer has a positive result on a urine drug screen that tests for common substances of abuse such as amphetamines, barbiturates, benzodiazepines, cocaine, opiates, and cannabinoids. (If positive on screen, confirmatory testing shall be performed where applicable) The volunteer has previous diagnosis of any serious psychiatric disorder. For this purpose, serious psychiatric disorder is defined as illness requiring hospitalization within the previous 12 months; routine administration of more than one medication to control anxiety, mood or sleep disorder; or history of suicide attempt The volunteer has received any blood products or immune globulin in the previous six months The volunteer has donated blood within the past 56 days