Active clinical trials for "Yellow Fever"

Phase 4 study to evaluate the immunogenicity and Safety of the 17DD Yellow Fever vaccine in HIV infected individuals, compared to non-HIV-infected individuals. Main objective: To compare the proportion of seroconversion and the geometric mean of neutralizing antibodies 30 days and 365 days after vaccine. Secondary objectives: To evaluate whether the titles of neutralizing antibodies are associated with CD4 lymphocyte counts, CD8 lymphocyte counts, CD4 nadir, HIV viral load and use of antiretroviral therapy. To assess the yellow fever vaccine viremia at day 10 after vaccine.To compare the incidence of adverse events in HIV-infected and non-HIV-infected individuals.

No antiviral treatment exists for yellow fever, only supportive care, and therefore we rely on prevention through vaccination. Although this vaccine is very effective, stockpiles are insufficient in outbreak situations and some people have a contraindication to be vaccinated. For those who are unprotected and at risk of yellow fever infection, treatment could be life saving.

We hypothesize that a high CD4+ and CD8+ T cell count will reduce viremia upon challenge with a structurally heterologous virus, and correspondingly result in reduced magnitude of host response to challenge infection. Primary Objective: To compare, after challenge with a structurally heterologous vaccine, the differences in levels of viremia between healthy adults who received primary vaccination with either YF17D vaccine, chimeric JE-YF17D vaccine, or inactivated JE vaccine. 58 subjects will be randomised into 1 of 2 arms (Arm B1 and Arm B2) in a 1:1 ratio, in a double-blind fashion. Subjects in Arm B1 will receive JE-YF17D vaccine (Imojev, Sanofi Pasteur) on Day 0 followed by YF17D vaccine (Stamaril, Sanofi Pasteur) on Day 28. Subjects in Arm B2 will receive Stamaril on Day 0 followed by Imojev on Day 28. Arm B3 will be conducted as a separate single-arm open label design in 14 subjects. Subjects in Arm B3 will receive inactivated JE vaccine (Ixiaro, Valneva) on Day 0 followed by Stamaril on Day 28. The rationale for these three study arms is as follows: Arm B1 will show the impact low levels of viremia, and the resultant low levels of virus-specific CD4+ and CD8+ T cells, would have on YF17D infection. In contrast, YF17D vaccination in Arm B2 would produce high levels of viremia, and in turn high levels virus-specific T cells, thus likely ameliorating JE-YF17D infection. Arm B3 will serve as the control arm, as vaccination with inactivated JE vaccine would not produce any YF17D-specific T cell response. Notably, the first vaccination in Arms B1 and B2 would also provide the viremia response in the absence of virus-specific T cells, which would serve as a reference point to interpret the outcome of the second vaccination.

The yellow fever vaccine is a live, attenuated virus that results in a robust immune response, especially in the T cell compartment. We have been studying immune responses to live viral infections using the yellow fever vaccine as a model for a live viral infection. In this study, we are interested in looking at the processing and lifespan of yellow fever specific CD8 T cells. We plan to accomplish this by measuring DNA replication and cell proliferation in humans using a naturally occurring stable isotope called deuterium (D20). This technique has been used to track the turnover of a number of human cell types in vivo. We plan to use D20 labeling to track YFV specific CD8+ T cells in human vaccinees who are positive for a specific HLA type, HLA A202. Deuterium labeled water (D2O), also known as heavy water is physically and chemically very similar to ordinary drinking water. In water, two hydrogen atoms bond to an oxygen and create H20. However in deuterated water, deuterium atoms replace the hydrogen atoms. Deuterium is a form of hydrogen that has an extra neutron. This neutron gives the atom extra weight, hence the name "heavy water." This extra weight can be detected in the lab with very sensitive instruments. Scientists have been using heavy water as a tracer to gain a better understanding of animal and human metabolic rates. Deuterium is in fact already in the water we drink daily. It is not radioactive, and it occurs naturally at a concentration of about 1 part per 5,000. Researchers have used heavy water since 1934 as a safe and effective tool in clinical trials.

To determine the efficacy of metformin in reducing the rate of symptomatic YF17D infection, and to elucidate the effects of metformin on YF17D viremia and the downstream adaptive immune response, we hereby propose a randomised, double-blind, placebo-controlled clinical trial that is coupled with a system biology approach. We plan to recruit 44 healthy volunteers aged 21-40 years, with a Body Mass Index of 20-25 kg/m2, have no known drug allergies and are not currently receiving regular immune-modulating therapy such as metformin, NSAIDs, paracetamol, corticosteroids or statins. The age range that we propose will ensure that our volunteers are likely to be healthy and not be on long-term medication for other concurrent medical conditions. This would abrogate the confounding effect of YF17D infection enhancement by cross reactive antibodies that we have previously shown. Informed written consent will be obtained before any physical examination is performed. All consented subjects will undergo screening which includes a full physical examination, vital signs measurement, clinical laboratory tests and urine pregnancy test (for female subjects of child-bearing potential) Eligible subjects will be randomized 1:1 to either metformin 1000mg or placebo twice daily for 7 consecutive days (Days 1-7). On Day 4, subjects will be administered one dose of YF17D before study drug dosing. Aim 1 tests the hypothesis that prophylactic metformin reduces ER stress and thus attenuates the post-infection pro-inflammatory response for reduced rate of symptomatic outcome. The primary objective for Aim 1 is to determine the efficacy of metformin in reducing the rate of symptomatic YF17D infection using a randomized placebo-controlled clinical trial. Aim 2 explores the effectiveness of metformin, either through its action on ER stress or other pathways that differentially regulate the expression of pro- and anti-viral host factors, in inhibiting live attenuated vaccine infection and downstream adaptive immune responses. The primary objective for Aim 2 is to elucidate the effects of metformin on YF17D viremia and the downstream adaptive immune response.

The goal of this study is to use the live attenuated yellow fever vaccine, YFV-17D (YF-VAX®, Sanofi-Pasteur) as a safe and effective model for viral infection to understand human immune response to viral antigens. Study participants will receive the yellow fever vaccine and participation in the study may be as short as one month or as long as one year, depending on immune responses.

Northern Argentina is a risk area for yellow fever (YF). Recent studies have suggested that immunity wanes in children vaccinated between 9 and 23 months of age. In 2015, a collaborative study conducted by the Ministry of Health (MoH) of Argentina, the Pan American Health Organization (PAHO), and the US Centers for Disease Control and Prevention (CDC) assessed the immunogenicity and safety of co-administration of YF and MMR vaccines in a pediatric population at 12-13 months of age. A total of 741 children presenting for routine immunization at 12-13 months of age enrolled and completed the study. It is now four to seven years since this pediatric group received their YF vaccinations. This cohort is unique because their initial YF vaccination and immune response to the vaccine dose are well characterized. Contact information collected during the earlier study will be used to locate the children. If consent is obtained, a 5ml specimen of blood will be collected and shipped to the CDC's Arboviral Diseases Reference Laboratory (ADRL) in Fort Collins, CO for plaque reduction neutralization testing using a 50% cut-off (PRNT50) to detect YF virus-specific neutralizing antibodies. Children with neutralizing antibody titers that are higher than their baseline titer collected approximately 28 days following YF vaccination will have PRNTs done for cross-reacting flaviviruses.

The goal of this clinical trial is to assess the immune response to the yellow fever vaccine 17D in adults with prior 17D vaccination. The main questions this study aims to answer are: how does prior vaccination affect antibody responses to re-vaccination? how does prior vaccination affect the immune cell response to re-vaccination? Participants will: have been previously vaccinated with 17D. be re-vaccinated with 17D. provide medical and travel histories. provide a blood sample prior to vaccination provide a blood sample approximately every other day for 14 days after vaccination. provide a blood sample approximately 28 days after vaccination. complete a daily diary of symptoms following vaccination for 14 days. report any additional symptoms after 14 days.

VYF03 is a phase II, randomized, parallel-group prevention study with 2 arms, active-controlled (Stamaril), observer-blind, multi-center study to assess the non-inferiority of the immune response, in terms of seroconversion rates of the investigational vaccine candidate vYF to the licensed Stamaril, in adults aged 18 years up to 60 years in Europe (EU). The safety and immunogenicity profile of vYF in a cohort of Asian population of Chinese origin outside of China will also be described. The study will also assess the immunogenicity profiles and the safety profiles of vYF and Stamaril. Participants will be randomized in a 2:1 ratio to receive a single subcutaneous injection of either the vYF vaccine (380 participants in EU and 80 participants of Chinese origin in Asia) or Stamaril (190 participants in EU and 40 participants of Chinese origin in Asia), on Day 01. The duration of each participant's participation will be approximately 5 years.

It concerns an investigation aiming to investigate genetic biological(s) marker(s) which allow to identify individuals who have risk of serious adverse events to the yellow fever vaccine. This testing is free of hypothesis, because these markers are still unknown. There is no intervention, and it is not possible to establish primary and secondary outcomes.