Phase 2 Shigella Vaccine and Challenge

Immunisation Clinical Trial

Official title: A Double-Blind Placebo Controlled Randomized Phase 2 Trial to Evaluate the Safety, Reactogenicity and Immunogenicity of a Live-Attenuated Shigella Sonnei Vaccine, WRSs2 and Determine Its Efficacy in a Challenge Model of S. Sonnei 53G in Healthy Adults

Status Active, not recruiting

Clinical Trial Summary

This is a trial to evaluate the safety, reactogenicity, immunogenicity and efficacy of a 10^6 cfu dose of an oral live-attenuated S. sonnei vaccine candidate, WRSs2, in up to 120 healthy males and non-pregnant females aged 18-49, inclusive. This is a two-phase study, an outpatient WRSs2 vaccination phase and an inpatient S. sonnei 53G challenge phase. After the initiation of the study, two participants had Grade 3 diarrhea and/or vomiting in the days following vaccination. The vaccination dose was reduced to 5X10^5, enrollment was changed to 2 arms and randomized 2:1 (vaccine: placebo). Participants with morbid obesity were excluded and weight loss medications prohibited. The Primary Objective of this study is to estimate combined vaccine efficacy of 2 doses of WRSs2 (10^6 cfu or 5X10^5 cfu) in preventing shigellosis, following challenge with S. sonnei strain 53G.

Clinical Trial Description

This is a double-blind, placebo controlled, randomized study to test the safety, reactogenicity, immunogenicity and efficacy of up to a 10^6 cfu dose of an oral live-attenuated S. sonnei vaccine (WRSs2) to protect against shigellosis after a targeted oral challenge with S. sonnei 53G, a virulent strain of S. sonnei. Up to 120 subjects, healthy males and non-pregnant females aged 18-49, will be enrolled and randomized in this study. Using the 10^6 CFU dose, subjects were randomized 1:1:1 into one of three vaccination arms to receive 2 doses of study agent 28 days apart. Arm 1 received 2 doses of WRSs2, Arm 2 received placebo followed by WRSs2 and Arm 3 received 2 doses of placebo. Twenty-eight (+2) days after the second dose of study agent, subjects were admitted to the inpatient unit and given an oral challenge of approximately 1500 cfu of 53G. The goal was to have 90 subjects (30 per arm) receive a challenge dose of 53G. The study duration is approximately 24 months with subject participation duration approximately 8 months.

After the initiation of the study, two participants had Grade 3 diarrhea and/or vomiting in the days following vaccination. The vaccination dose was reduced to 5X10^5, enrollment was changed to 2 arms and randomized 2:1 (vaccine: placebo). Participants with morbid obesity were excluded and weight loss medications prohibited.

The Primary Objective of this study is to estimate combined vaccine efficacy of 2 doses of WRSs2 (10^6 cfu or 5X10^5 cfu) in preventing shigellosis, following challenge with S. sonnei strain 53G. The Secondary Objectives are to:1) Estimate vaccine efficacy of 1 dose of 10^6 cfu, 2 doses of 10^6 cfu, and 2 doses of 5x10^5 cfu of WRSs2 in preventing shigellosis following challenge with S. sonnei strain 53G. 2) Evaluate the safety of WRSs2; 3) Evaluate immune responses following vaccination (immunogenicity) with WRSs2 and after challenge with S. sonnei strain 53G by serum anti-LPS and anti-Invaplex IgG and IgA by ELISA; 4) Determine fecal shedding of S. sonnei after WRSs2 vaccination and 53G challenge by qualitative stool culture. ;

Related Conditions & MeSH terms

• Dysentery, Bacillary
• Immunisation
• Shigella Infection

• NCT number: NCT04242264
• Study type: Interventional
• Source: National Institute of Allergy and Infectious Diseases (NIAID)
• Status: Active, not recruiting
• Phase: Phase 2
• Start date: October 12, 2022
• Completion date: July 31, 2024