A Phase 1 interventional study of Typhoid VI Polysaccharide Vaccine Injectable Solution and Saline Placebo (0.5mL injection) in Posttraumatic Stress Disorder (PTSD), sponsored by University of California, San Francisco. Recruiting at 1 site in United States. Open to participants aged 18 Years to 65 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-09-21.
Sponsored by University of California, San Francisco · Phase 1, Interventional, and Basic science
The goal of this study is to learn if short-term changes in the immune system alter how we process information and experience fear. The main questions it aims to answer are:
Do people who receive typhoid vaccine respond differently than those who receive a placebo saline vaccine? Do people who receive typhoid vaccine experience changes in how they think and feel?
Participants will:
Attend four appointments at the San Francisco VA Health Care System;
Receive typhoid vaccine or placebo at one of the visits;
Have their physiological responding measured while listening to sounds;
Complete questionnaires and psychological tests.
Posttraumatic stress disorder (PTSD) is a chronic disorder affecting more than 8% of the general population and two-three times as many women as men. Deficits in fear responding play a critical role in PTSD. Interventions that target fear responding are first-line treatments for PTSD, but they are only partially effective. To develop new and enhanced interventions, we need a better understanding of the factors that influence fear responding in PTSD in both females and males. One such factor is inflammation, which is elevated in response to acute psychological stress and in PTSD. Preclinical models indicate that elevated inflammation in general, and elevated levels of the pro-inflammatory cytokine interleukin-6 (IL-6) in particular, can impair fear responses. People with PTSD and women may be more sensitive to the effects of inflammatory activity on fear responses. The long-term goal is to uncover the mechanistic role that inflammation plays in PTSD in order to identify effective primary and adjunctive anti-inflammatory interventions. The objective in this proposal is to determine the effects of acute inflammatory challenge on fear responding in trauma-exposed women and men with and without PTSD. The central hypothesis is that acute inflammatory challenge will alter fear responding, with particularly strong effects in people with chronic PTSD and women. The aims are to: 1) determine the effects of acute inflammatory challenge on fear responding in individuals with and without PTSD; 2) examine if increases in inflammatory activity mediate associations between acute inflammatory challenge and fear responses; and 3) elucidate sex differences in the effects of acute inflammatory challenge on fear responses. In the proposed study, we will use polysaccharide typhoid vaccine, which preliminary data support as a robust acute inflammatory challenge, and a fear learning paradigm that we have used in >200 people with PTSD. Participants will first undergo physiological testing of fear responses. Then, three days later, participants will receive either vaccine or placebo and undergo more tests, including physiological tests. One week later, we will test physiological responses again. Inflammatory markers will be measured at baseline, twice on the the vaccine/placebo day, and once at the one-week follow-up visit. This proposal is significant and innovative because it would be the first study to examine the effects of acute inflammatory activity on fear responses in trauma-exposed individuals with and without PTSD, and it has potential to elucidate biological mechanisms of impaired fear responses, uncover sex differences, and point us in the direction of novel interventions to treat PTSD.
2,682 studies on the registry are indexed under Stress Disorders, Post-Traumatic; 601 are open to participants now.
This study's planned enrollment of 288 is above the median of 69 across 2,196 interventional studies indexed under Stress Disorders, Post-Traumatic.
Browse Stress Disorders, Post-Traumatic studies →University of California, San Francisco is the lead sponsor of 2,169 studies on the registry; 372 are open to participants now.
Of its 267 completed or terminated interventional studies of FDA-regulated products, 202 (76%) have results posted.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
All Subjects:
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants in this condition will receive an injection of 0.5ml Salmonella typhi capsular polysaccharide vaccine (Sanofi Pasteur, SA), which contains 25μg of purified Vi polysaccharide in a colorless isotonic phosphate buffered saline (pH 7±0.3), 4.150mg of sodium chloride, 0.065mg of disodium phosphate, 0.023mg of monosodium phosphate and 0.5ml of sterile water for injection.
Biological: Typhoid VI Polysaccharide Vaccine Injectable Solution
Participants in this condition will receive and injection of 0.5ml of saline.
Other: Saline Placebo (0.5mL injection)
Salmonella typhi capsular polysaccharide vaccine (Typhoid Vi Polysaccharide Vaccine): Each dose of 0.5ml Salmonella typhi capsular polysaccharide vaccine (Sanofi Pasteur, SA) is formulated to contain 25μg of purified Vi polysaccharide in a colorless isotonic phosphate buffered saline (pH 7±0.3), 4.150mg of sodium chloride, 0.065mg of disodium phosphate, 0.023mg of monosodium phosphate and 0.5ml of sterile water for injection. It is indicated for use by humans aged 2 years and older for protection against typhoid fever.
The placebo injection will consist of 0.5mL of saline.
Skin conductance response (SCR)
Skin conductance level (SCL)will be sampled at 1000 Hz beginning 2 s prior to the conditioned stimulus (CS) onset and continuing until 6 s following CS offset. The skin conductance response (SCR) score for each CS interval will be obtained by subtracting the mean SCL for the 2 s preceding CS onset from the peak during the 8 s CS interval.
Time frame: SCR will be assessed at baseline, 4.5 hours, and one week after vaccine/placebo.
Heart rate
HR will be calculated by subtracting average HR of every 0.5 s interval during 6 s before CS (baseline) from peak HR during 0.5 s interval of 8 s after CS onset (response).
Time frame: HR will be assessed at baseline, 4.5 hours, and one week after vaccine/placebo.
Eyeblink electromyography (EMG)
EMG will be calculated by subtracting the mean signal amplitude during 2 s preceding CS onset (baseline) from the peak during the 8 s CS interval (response).
Time frame: Eyeblink EMG will be assessed at baseline, 4.5 hours, and one week after vaccine/placebo.
Plan to share: Yes — Demographic, clinical, biological, and psychophysiological data will be acquired from 120 individuals with PTSD and 120 individuals without PTSD. Demographic data will be self-reported. Clinical data will include information from validated semi-structured clinical interviews and validated self-report measures assessing symptoms of PTSD and other psychiatric disorders. Biological data will include levels of eleven inflammatory markers derived from five blood draws for each participant. Psychophysiological data will include skin conductance level, heart rate (HR), and HR variability (HRV) assessed 34 times for each participant.
Supporting information: Study protocol, Informed consent form
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Studies of the drug tested here: Vi polysaccharide vaccine, typhoid
Stress Disorders, Post-Traumatic →
University of California, San Francisco →