This was a randomized, double-blind, ascending dose study conducted at a single clinical research center.
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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
DOUBLE
Enrollment
45
Placebo is administered to the control group on Day 0 and 28
A single dose of commercial typhoid fever vaccine Typhim Vi is administered on Day 0, followed by placebo control on Day 28
Number of participants reporting solicited injection site and systemic events and unsolicited adverse events following vaccination with Typhax
Solicited Injection Site reactions: Pain, Tenderness, Erythema, Induration; Solicited Systemic Reactions Fever, Headache, Joint Pain, Joint Swelling, Fatigue, Myalgia, Nausea, Vomiting, Diarrhea
Time frame: Days 0 up to Day 56 (= 28 Days post second vaccination)
Number of participants reporting adverse events following vaccination with Typhax
Adverse events are assessed at study visits by PI for seriousness, relationship to investigational product , severity and other possible etiologies
Time frame: Days 0 up to Day 210
Anti-Vi IgG antibody seroconversion and geometric mean antibody titers
The immunogenicity will be measured by ELISA for anti-Vi percent seroconversion and GMTs before and at day 14 after vaccination.
Time frame: Day 0 - Day 14
Anti-Vi IgG antibody seroconversion and geometric mean antibody titers
The immunogenicity will be measured by ELISA for anti-Vi percent seroconversion and GMTs before and at day 28 after vaccination.
Time frame: Day 0 - Day 28
Anti-Vi IgG antibody seroconversion and geometric mean antibody titers
The immunogenicity will be measured by ELISA for anti-Vi percent seroconversion and GMTs before and at day 42.
Time frame: Day 0 - Day 42
Anti-Vi IgG antibody seroconversion and geometric mean antibody titers
The immunogenicity will be measured by ELISA for anti-Vi percent seroconversion and GMTs before and at day 180.
Time frame: Day 0 - Day 180.
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Vi-specific B-cell ELISPOT responses
Immunogenicity was evaluated by comparing the number of Vi-specific B-cells by ELISPOT in PBMC samples
Time frame: Days 0 through 38