View clinical trials related to Yellow Fever.
Filter by: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.
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.
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 study is designed as a Phase III, double-blind, multi-center, randomized, active-controlled study in which four groups of participants (n=554 per group) will receive either one of three different manufacturing lots of SII-YFV or STAMARIL® - a licensed and WHO pre-qualified YFV.
The study is designed as a Phase III, double-blind, multicenter, randomized, active-controlled, parallel-group design in which two groups of participants will receive either SII-YFV or STAMARIL® - a licensed and WHO pre-qualified YFV. The study will start only after the approval from the applicable ethics committees and national regulatory agencies.
Yellow fever is an acute febrile infectious disease transmitted to man urban cycle by mosquitoes infected by an arbovirus of the genus Flavivirus family Flaviviridae. Its occurrence is recorded in South America Central America and Africa. In cities the yellow fever vector is the Aedes aegypti mosquito which also transmits dengue viruses zika and chikungunya. This disease is more frequent in males and the most affected age group is above fifteen years due to the greater exposure related to the penetration in wild areas of the endemic zone of yellow fever. Another risk group is unvaccinated people who live near wild environments where the virus circulates. According to the World Health Organization a single dose of the yellow fever vaccine is sufficient to maintain protective immunity against yellow fever for a lifetime therefore a booster dose is not required. This question is difficult to evaluate because there is no serological correlate of protection against yellow fever and seropositivity is defined with several cut off points. Although studies indicate that the duration of protection after vaccination is long there is considerable evidence in the literature that antibody titer falls over the years reaching levels considered as seronegative in at least a portion of the vaccinees. This is of more concern to people living in endemic areas who are exposed to the virus throughout their lives. For this reason Brazil recommended revaccinating once at least until additional studies were done. The need to increase Bio Manguinhos production capacity to meet the increased demand from Brazil and other countries is urgent. The occurrence of epidemics when millions of individuals need to be vaccinated in a short period of time exceeds production capacity and this is a recurrent problem. The current vaccine has a very high potency well above the thousand international units recommended by World Health Organization. But we need to generate additional evidence that very low doses of viral particles in the yellow fever vaccine are still immunogenic and that their immunogenicity can be maintained for at least ten years after vaccination. This evidence will support the rapid increase of their availability by the fractionation of doses or other alternatives.
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.
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.
Travelers (n = 30, 15 taking low-dose methotrexate (MTX), 15 healthy controls (HC), seeking travel advice in one of the following Swiss Travel Centers (Aarau, Basel, Bern, Geneva, Lausanne, Zurich) and who have an indication for yellow fever (YF) vaccination according to the Swiss Federal Office of Public Health's vaccination recommendations are invited to participate in this study. After signing the consent form (i) YF viremia and (ii) anti-YF antibody production in patients taking low-dose MTX and HC will be compared after YF vaccination. It will be analyzed whether the percentage of people with protective antibodies differs between the two groups and (iii) vaccine side effects will be compared between the groups.
The yellow fever vaccine is a live, attenuated virus that results in a robust immune response, especially in the T cell compartment. The researchers 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, the researchers are interested in looking at the processing and lifespan of yellow fever specific CD8 T cell by measuring DNA replication and cell proliferation in humans using a naturally occurring stable isotope called deuterium.