GMT of TNA NF50 at Day 64 in AV7909 study groups (Lots 1, 2 and 3) and BioThrax group. The outcome measure in AV7909 study groups was assessed for AV7909 lot-to-lot consistency, which was based on GMT TNA NF50 response at Day 64, wherein the 95% confidence interval (CI) for ratios of geometric mean titer (GMT) of TNA NF50 at Day 64 (seven weeks after second AV7909 vaccination) for each of the three AV7909 lot-to-lot comparisons had to be within equivalence margin of 0.5 and 2.0.

Proportion of participants with TNA NF50 ≥0.56 at Day 64 in each AV7909 study groups (Lot 1, Lot 2, Lot 3). The assessment of the immune response in each study group was pre-defined as the lower bound of the two-sided 95% CI to be ≥40% for the percentage of AV7909 participants in each of the three lots achieving a TNA NF50 ≥0.56 at seven weeks after second AV7909 vaccination (Day 64).

Percentage of AV7909 participants (from all three AV7909 study groups pooled) achieving a TNA NF50 ≥0.56 on Day 64 (seven weeks after second AV7909 vaccination). The assessment of the immune response in AV7909 participants was pre-defined as the lower bound of the two-sided 95% CI for proportion of AV7909 participants with TNA NF50 ≥0.56 at Day 64 ≥40%.

Proportion of AV7909 participants (in each AV7909 study groups) and BioThrax participants who achieved TNA NF50 ≥0.29 at Day 64. Non-inferiority of AV7909 vaccine to BioThrax vaccine at Day 64 was assessed as determined by the two-sided lower bound for the 95% CI of the difference in the percentage of AV7909 participants (three lots pooled) with a TNA NF50 ≥0.29 and the percentage of BioThrax participants with a TNA NF50 ≥0.29 being greater than -15%.

Number of AV7909 participants or BioThrax participants who received at least one vaccination and reported serious adverse event(s) (SAEs) from the time of the first vaccination on Day 1 through Day 394.

Based on serum concentrations of ciprofloxacin on Day 8 (pre-AV7909 vaccination) and on Day 35 (post-AV7909 vaccination), steady state AUC0-12h and Cmax were derived, and geometric mean of ratio of AUC0-12h on Day35/Day 8 and geometric mean of ratio for Cmax on Day 35/Day8, and the corresponding 90% CI of the mean ratios were calculated.

Based on serum concentrations of doxycycline on Day 8 (pre-AV7909 vaccination) and on Day 38 (post-AV7909 vaccination), steady state AUC0-12h and Cmax were derived, and geometric mean of ratio of AUC0-12h on Day38/Day 8 and geometric mean of ratio for Cmax on Day 38/Day8, and the corresponding 90% CI of the mean ratios were calculated.

Immunogenicity measured by the lower bound (LB) of the 95% confidence intervals (CIs) for the proportion of subjects in each study arm with Day 63 TNA 50% neutralization factor (NF50) values greater than or equal to threshold

Incidence of adverse events (including assessment of symptoms, physical exam findings, clinical laboratory tests, and vital signs) from the time of the first immunization on Day 0 through Day 84

Incidence of solicited systemic reactions and solicited injection site reactions each day for 7 days following each vaccination using subject e-diaries by severity. Reactions were graded using the following scale (note, for redness and swelling, the diameter \[greater of two perpendicular measurements\] was assessed by the subject using an injection site measurement tool): Grade 0 (Absent): Symptom not present; Grade 1 (Mild): Symptom present but does not interfere with activities of daily living, or affected area (redness, swelling) measures \<3 cm; Grade 2 (Moderate): Symptom causes some interference with activities of daily living, or affected area (redness, swelling) measures 3 - 10 cm; Grade 3 (Severe): Symptom prevents activities of daily living or requires treatment, or affected area (redness, swelling) measures \> 10 cm. For each reaction, subjects are counted once across all vaccinations at the highest reported level of severity.

Incidence of clinical laboratory abnormalities throughout the study (up to Day 84). Clinical laboratory abnormalities are presented as the total of Grade 1 (mild), Grade 2 (moderate), Grade 3 (severe), and Grade 4 (potentially life-threatening) abnormalities according to criteria adapted from the U.S. Department of Health and Human Services, Food and Drug Administration, Center for Biologics Evaluation and Research: Guidance for Industry. Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled in Preventive Vaccine Clinical Trials (September 2007). Within each laboratory parameter, subjects are counted once for their most severe occurrence of clinical laboratory abnormality.

Incidence of immunologically significant adverse events of special interest as defined by the Center for Biologics Evaluation and Research from the time of the first immunization on Day 0 through the 12-month safety follow-up telephone call following the last scheduled vaccination