Due to recent concern of biowarfare and bioterrorism, the US government is making efforts to improve its ability to protect citizens against the smallpox virus. This study will evaluate safety of IMVAMUNE®, an investigational smallpox vaccine, and its ability to stimulate the immune system (the body's defense system). Two vaccine preparations have the same name but one is a liquid and one is a powder that has liquid added just before it is given. The vaccine that comes as a liquid will be injected (given as a shot) just under the skin (subcutaneously) or injected between the layers of the skin (intradermally). The powder formulation is only injected just under the skin. Approximately 495 adults, age 18 older born after 1971, which have not had smallpox vaccine before, may participate in the study for about 7 months.

Smallpox was declared officially eradicated by the World Health Assembly in 1980. Despite the fact that the World Health Organization (WHO) officially declared smallpox to be eradicated, a new threat exists due to the potential use of variola virus as an agent for biological warfare and/or bio-terrorism. Following the events of September 11, 2001 the Division of Microbiology and Infectious Diseases/National Institute of Allergy and Infectious Diseases contracted for the advanced development of IMVAMUNE®. Initially, a lyophilized formulation was manufactured, which was reconstituted 'at the bedside' prior to administration in clinical and non-clinical settings. Due in part to the potential requirement for mass vaccinations coupled with the increased manufacturing time and other constrains associated with lyophilization, it was decided to transition to a liquid product formulation. Therefore, after 2005, clinical and non-clinical efforts have focused largely on the liquid formulation, though non-clinical studies with the lyophilized formulation continued. Presently, due to the potential need to be able to stockpile Modified Vaccinia Ankara (MVA) for an extended period of time, there is renewed interest in the lyophilized formulation. The purpose of this study is to compare the safety and immunogenicity of lyophilized IMVAMUNE® [1x10^8 tissue culture infectious dose 50 (TCID50)] versus liquid formulation IMVAMUNE® (1x10^8 TCID50) administered by the subcutaneous (SC) route and a lower dose liquid formulation IMVAMUNE® (2x10^7 TCID50) administered by the intradermal (ID) route in healthy vaccinia-naïve individuals. This study is designed as a randomized, non-placebo controlled, partially-blinded study (liquid versus lyophilized formulation by the SC route Group B versus A). The study staff is unblinded to Group C. The study will contain 3 arms: Group A [Number (N)=165] will receive a 2 dose regimen of IMVAMUNE® (1x10^8 TCID50/0.5 mL per dose) lyophilized formulation by the SC route on Day 0 and 28. Group B (N=165) will receive a 2 dose regimen of IMVAMUNE® (1x10^8 TCID50/0.5 mL per dose) liquid formulation by the SC route on Day 0 and 28. Group C (N=165) will receive a 2 dose regimen of IMVAMUNE® (2x10^7 TCID50/0.1 mL per dose) liquid formulation by the ID route on Day 0 and 28. Safety will be measured by assessment of solicited local and systemic reactions within 15 days after each vaccination (Day 0-14), unsolicited adverse events for 28 days following the second vaccination (56 days following the initial vaccination for those subjects that fail to receive the second vaccination), and serious adverse events through six months post the final vaccination. Immunogenicity testing will include assessment of vaccinia-specific plaque reduction neutralizing antibody titers (PRNT) and enzyme linked immunosorbent assay (ELISA) mean geometric titers (GMT) based on individual peak titers. For each subject, the peak PRNT or ELISA will be defined as the largest titer among all available measurements post second vaccination.

Inclusion Criteria:

Inclusion criteria that must be met prior to the initial vaccination:

• At least 18 years of age and born after 1971.

• Read, signed, and dated informed consent document.

• Available for follow-up for the planned duration of the study (6 months after last immunization).

• Acceptable medical history by screening evaluation and limited physical assessment.

• If the subject is female and of childbearing potential, negative serum pregnancy test at screening and negative urine or serum pregnancy test within 24 hours prior to vaccination.

• If the subject is female and of childbearing potential, she agrees to use acceptable contraception, and not become pregnant for 28 days following the last vaccination:

  1. A woman is considered of childbearing potential unless post-menopausal (greater than or equal to 1 year) or surgically sterilized (tubal ligation, bilateral oophorectomy, or hysterectomy).
  2. Acceptable contraception methods are restricted to effective devices [intrauterine devices (IUD)s, NuvaRing®] or licensed hormonal products with use of method for a minimum of 30 days prior to vaccination, abstinence from sexual intercourse with men (vaginal penetration by a penis, coitus), and monogamous relationship with a vasectomized partner.

• Negative enzyme linked immunosorbent assay (ELISA) for human immunodeficiency virus (HIV).

• Alanine aminotransferase (ALT) <1.25 times institutional upper limit of normal.

• Negative hepatitis B surface antigen and negative antibody to hepatitis C virus.

• Negative urine glucose and urine protein <1 plus by dipstick or urinalysis.

• Adequate renal function is defined as a serum creatinine not exceeding the institution's upper limit of normal.

• Electrocardiogram (ECG) in absence of clinical significance (e.g., complete left or right bundle branch block, incomplete left bundle branch block or sustained ventricular arrhythmia, or 2 premature ventricular contraction's (PVC)'s in a row, or sympathetic tonus (ST) elevation consistent with ischemia).

• The following blood parameters:

  1. Hemoglobin equal or above the lower limit of institutional normal (sex-specific);
  2. White blood cells greater than 2,500 and less than 11,000/mm^3;
  3. Platelets greater than or equal to 140,000/mm^3.

• Weight: greater than or equal to 110 pounds.

Inclusion Criteria that must be met prior to the second vaccination:

• Acceptable medical history.

• If the subject is female and of childbearing potential, negative urine or serum pregnancy test within 24 hours prior to vaccination.

• If the subject is female and of childbearing potential, she agrees to use acceptable contraception, and not become pregnant for 28 days following the last vaccination:

  1. A woman is considered of childbearing potential unless post-menopausal (greater than or equal to 1 year) or surgically sterilized (tubal ligation, bilateral oophorectomy, or hysterectomy).
  2. Acceptable contraception methods are restricted to effective devices (IUDs, NuvaRing®) or licensed hormonal products with use of method for a minimum of 30 days prior to vaccination, abstinence from sexual intercourse with men (vaginal penetration by a penis, coitus), and monogamous relationship with a vasectomized partner.

Exclusion Criteria:

Exclusion criteria that apply prior to the initial vaccination:

• History of immunodeficiency

• Typical vaccinia scar

• Known or suspected history of smallpox vaccination including Modified Vaccinia Ankara (MVA) alone or as a vector as well as other investigational smallpox vaccine

• Military service prior to 1991 or after January 2003

• Known or suspected impairment of immunologic function including, but not limited to, clinically significant liver disease, diabetes mellitus, or moderate to severe kidney impairment

• Malignancy not including squamous cell skin cancer or basal cell skin cancer unless at the vaccination site or history of skin cancer at the vaccination site

• Active autoimmune disease

  a. Persons with vitiligo or thyroid disease (e.g., taking thyroid hormone replacement) are not excluded

• History of myocardial infarction, angina, congestive heart failure, cardiomyopathy, stroke or transient ischemic attack, or other heart condition under the care of a doctor

• Systolic blood pressure greater than or equal to 150 mmHg or diastolic blood pressure greater than or equal to 100 mmHg

• Ten percent or greater risk of developing a myocardial infarction or coronary death within the next 10 years using the National Cholesterol Education Program's risk assessment tool (http://hp2010.nhlbihin.net/atpiii/calculator.asp)

NOTE that this criterion applies only to subjects 20 years of age and older AND only if at least one of the following apply:

a. have smoked a cigarette in the past month, and/or b. have hypertension (defined as systolic blood pressure >140 mm Hg) or are on antihypertensive medication, and/or c. have a family history of coronary heart disease in male first-degree relative (father or brother) <55 years of age or a female first-degree relative (mother or sister) <65 years of age

• High-dose steroid use for greater than 2 weeks duration within three months prior to vaccination and current use of immunosuppressive medication

  1. Corticosteroid nasal sprays are permissible
  2. Persons who are using a topical steroid can be enrolled after their therapy is completed
  3. Inhaled steroids for asthma are not permissible

• Medical or psychiatric condition or occupational responsibilities that preclude subject compliance with the protocol

• Any history of illegal injection drug use

• Receipt or planned receipt of inactivated vaccine from 14 days prior to the first vaccination through 14 days post second vaccination

• Receipt or planned receipt of any other live attenuated vaccine within 30 days prior to the first vaccination through 30 days post second vaccination

• Use of any other experimental agent within 30 days prior to vaccination and for the duration of the study

• Receipt of blood products or immunoglobulin within six months prior to vaccination

• Donation of a unit of blood within 56 days prior to vaccination and prior to Visit 6

• Acute febrile illness (greater than or equal to 100.4 degrees Fahrenheit) on the day of vaccination

• Pregnant or lactating women

• Eczema of any degree or history of eczema

• Active atopic dermatitis, active exfoliative skin disorders/conditions, current Varicella zoster, or any acute skin disorders of large magnitude, e.g., laceration requiring sutures, burn greater than 2×2 cm

• Any condition that, in the opinion of the investigator, might interfere with study objectives

• Known allergy to IMVAMUNE® vaccine

• Known allergy to egg or aminoglycoside (including gentamicin)

• Study personnel

Exclusion criteria that apply prior to the second vaccination:

• Continued inflammation (erythema and/or induration) graded as moderate or severe at the site of the initial vaccination

• History of immunodeficiency

• Known or suspected impairment of immunologic function including, but not limited to, clinically significant liver disease, diabetes mellitus, or moderate to severe kidney impairment

• Malignancy not including squamous cell skin cancer or basal cell skin cancer unless at the vaccination site or history of skin cancer at the vaccination site

• Active autoimmune disease

  a. Persons with vitiligo or thyroid disease (e.g., taking thyroid hormone replacement) are not excluded

• History of myocardial infarction, angina, congestive heart failure, cardiomyopathy, stroke or transient ischemic attack, or other heart condition under the care of a doctor

• Systolic blood pressure greater than or equal to 150 mmHg or diastolic blood pressure greater than or equal to 100 mmHg

• High-dose steroid use for greater than 2 weeks duration within three months prior to vaccination and current use of immunosuppressive medication.

  1. Corticosteroid nasal sprays are permissible
  2. Persons who are using a topical steroid can be enrolled after their therapy is completed
  3. Inhaled steroids for asthma are not permissible

• Medical or psychiatric condition or occupational responsibilities that preclude subject compliance with the protocol

• Any history of illegal injection drug use

• Receipt of or planned receipt of inactivated vaccine from 14 days prior to vaccination through 14 days post second vaccination

• Receipt of or planned receipt of any other live attenuated vaccine from 30 days prior to vaccination through 30 days post second vaccination

• Use of any other experimental agent within 30 days prior to vaccination and for the duration of the study

• Receipt of blood products or immunoglobulin within six months prior to vaccination

• Donation of a unit of blood within 56 days prior to vaccination and prior to Visit 6

• Acute febrile illness (greater than or equal to 100.4 degrees Fahrenheit) on the day of vaccination

• Pregnant or lactating women

• Eczema of any degree or history of eczema

• Active atopic dermatitis, active exfoliative skin disorders/conditions, current Varicella zoster, or any acute skin disorders of large magnitude, e.g., laceration requiring sutures, burn greater than 2×2 cm

• Any condition that, in the opinion of the investigator, might interfere with study objectives

• Known allergy to IMVAMUNE® vaccine

• Known allergy to egg or aminoglycoside (including gentamicin)