Safety and Immunogenicity of Typhax, a Typhoid Vaccine

A Phase 1, Randomized, Double-Blind, Placebo-Controlled Dose Escalation Trial to Determine the Safety and Immunogenicity of Typhax Delivered IM

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.

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

Adverse events are assessed at study visits by PI for seriousness, relationship to investigational product , severity and other possible etiologies

The immunogenicity will be measured by ELISA for anti-Vi percent seroconversion and GMTs before and at day 14 after vaccination.

The immunogenicity will be measured by ELISA for anti-Vi percent seroconversion and GMTs before and at day 28 after vaccination.

The immunogenicity will be measured by ELISA for anti-Vi percent seroconversion and GMTs before and at day 42.

The immunogenicity will be measured by ELISA for anti-Vi percent seroconversion and GMTs before and at day 180.

Immunogenicity was evaluated by comparing the number of Vi-specific B-cells by ELISPOT in PBMC samples

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

Cartee RT, Thanawastien A, Griffin Iv TJ, Mekalanos JJ, Bart S, Killeen KP. A phase 1 randomized safety, reactogenicity, and immunogenicity study of Typhax: A novel protein capsular matrix vaccine candidate for the prevention of typhoid fever. PLoS Negl Trop Dis. 2020 Jan 6;14(1):e0007912. doi: 10.1371/journal.pntd.0007912. eCollection 2020 Jan.