Safety and Immunogenicity of Typhax, a Typhoid Vaccine

Healthy adult subjects aged 18 to 55 years were assigned to 3 ascending dose cohorts of Typhax (0.5, 2.5 or 10 mcg Vi antigen). Groups of 15 subjects in each dose cohort were randomized to receive Typhax, Typhim Vi (25 mcg Vi antigen) or placebo (saline) in a ratio of 3:1:1, respectively. Typhax and placebo (saline) was administered as two dose regimen (Days 0 and 28), and Typhim Vi was given as a single dose (Day 0) with matching placebo on Day 28. All doses were administered by a unblinded third-party as 0.5 mL by intramuscular (IM) injection. Safety and reactogenicity endpoints was assessed at 14 and 28 days after the first Typhax vaccination and 14 days after the second vaccination. Immunogenicity was assessed using an enzyme-linked immunosorbent assay (ELISA) to measure anti-Vi antibody serum titers on days 0, 14, 28, 42 and 180. A positive immune response (seroconversion) by ELISA is defined as at least a 4-fold increase over baseline in the Vi-specific ELISA.

Inclusion criteria

• Healthy adult men or women who are not pregnant or planning to become pregnant during study duration aged 18 to 55 years.
• Clinical laboratory parameters within normal laboratory limits or not found to be clinically significant by the PI

Exclusion criteria

• Relevant history of physical or psychiatric illness or medical disorder that required treatment.
• Known or suspected hypersensitivity to investigational product
• Immunocompromised subjects
• Previous Typhoid vaccination or elevated anti-Vi antibodies at screening
• Known history of Typhoid infection in the previous 6 months
• Positive HIV, HBsAg, or HCV screen
• Any other condition or abnormality that, in the opinion of the Investigator, may compromise the safety of the patients