View clinical trials related to Yellow Fever.
Filter by:This study evaluates seroconversion against measles, mumps, rubella and yellow fever following vaccination. One-third of children will receive both yellow fever and measles, mumps, and rubella (MMR) vaccines on the same day; one- third of children will receive MMR vaccine at enrollment followed by yellow fever vaccine 4 weeks later; one-third of children will receive yellow fever vaccine at enrollment followed by MMR vaccine 4 weeks later.
The main purpose of this study is to assess the immunogenicity and safety of the concomitant and sequential administration of yellow fever (YF) vaccine and tetravalent dengue vaccine (TDV) in healthy participants aged 18 to 60 years living in country non-endemic for both dengue and YF.
Yellow fever is an acute viral disease transmitted by mosquitoes in South America, Central America and Africa. It is more prevalente in males gender and the age above 15 years due to the greater exposure in the wild endemic area of yellow fever. According to the World Health Organization (WHO), 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 issue 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, many studies have demonstrated a reduction of the antibody titrer over the years. Consequently, there is more concern about people who live in endemic areas. For this reason, Brazil recommends revaccinating once at least until additional studies are performed. It is important to know the duration of immunity induced by lower doses of YF vaccine. In our knowledge, there is a lack of clinical studies evaluating the immunity duration of the yellow fever vaccine with lower doses. This information is relevant to subsidize the routine recommendation of YF vaccine fractional dose for adults.
Since the 1st pandemic of the 21st century caused by SARS coronavirus, the world has experienced outbreaks of swine origin H1N1 influenza, Ebola and Zika viruses, which have all resulted in global health crises. Rapid mass vaccination with an effective vaccine such as a live attenuated vaccine, of vulnerable immune-naïve populations to establish herd immunity is an approach to control outbreaks. Such live attenuated vaccine had been used with great success in sporadic yellow fever outbreaks and recently successfully employed in Ebola field trial, both of these diseases have the potential for pandemic spread. Indeed, live attenuated vaccines have proven especially effective in controlling childhood diseases and have even succeeded in eradicating polio and measles from most parts of the world. However, deployment of such vaccines for pandemic control cannot be limited to children but must include adults in order to rapidly elevate herd immunity rates to halt transmission. Vaccinating adults may produce efficacy rates significantly different to those observed in children due to the prevalence of chronic diseases and their associated metabolic complications. Presently, there are 1 billion people who are overweight, many suffer from concurrent metabolic disorders. As activation of the adaptive immunity is reliant on a robust innate immune response to vaccines, metabolic disorders and long-term anti-inflammatory therapy with interventions such as statins may reduce vaccine immunogenicity resulting in suboptimal efficacy in this subpopulation. This study would therefore test the hypothesis that statins reduce live attenuated vaccine immunogenicity. We will combine a clinical trial with systems vaccinology approaches to define the impact statins has on the innate immune, B and T-cell responses to live attenuated vaccination. Our study will thus extend upon another recently completed trial by us and will provide new insights into the determinants of vaccine efficacy in a rapidly growing and aging population globally
In July 2016, the demand for yellow fever vaccines in response to the large urban outbreaks occurring concurrently and the risk of further spread through the African continent and even to Asia, was larger than the available supply. In this situation, the World Health Organization (WHO) developed recommendations for the use of fractional-dose of yellow fever vaccine as a dose-sparing strategy. These recommendations were based on limited number of clinical trials and additional studies should assess the applicability of the fractional dose to all WHO-prequalified vaccines, the persistence of neutralizing antibodies and the performance of the fractional dose in young children and populations in Africa including those with HIV. This study aims to respond to some of the research questions that would allow broadening the recommendations on the use of fractional doses of yellow fever vaccine in emergency situations. The study will be conducted in Uganda and Kenya and the main objective is to assess the non-inferiority is seroconversion 28 days after vaccination of a fractional dose compared to full dose for each WHO-prequalified manufacturer. As secondary objectives the study will assess seroprotection 10 days and 1 year after vaccination, to assess rapidity and persistence of protective antibody levels; describe the geometric mean titre and the change in neutralizing antibody on Day 28 days after vaccination with fractional and full doses; and assess the occurrence of adverse events and serious adverse events (SAE) during 28 days after administration of fractional and full doses. The study consists of a randomized non-inferiority trial. The study aims to start in April 2017 in the two sites and aims to recruit 960 adults. Results for the main outcome will be reviewed by the study Data and Safety Monitoring Board and one vaccine will be selected for the studies in children and HIV positive adults.
This study is a multi-center, double-blind, placebo-controlled, Phase I study to evaluate the safety, reactogenicity, tolerability, and immunogenicity of Modified Vaccinia Ankara-Bavarian Nordic-Yellow Fever (MVA-BN-YF) in Flavivirus-naive healthy male and non-pregnant female adult subjects. There are six dose groups in this study. Subjects who have never received a licensed or investigational smallpox vaccine will be randomized to Groups 1-5 and vaccine administration and follow-up will be conducted in a double-blinded fashion. Subjects who have previously received two, 1 x 10^8 TCID50 doses of Modified Vaccinia Ankara-Bavarian Nordic (MVA-BN) between 19 and 45 days apart by s ubcutaneous (SC) or intramuscular (IM) routes will be enrolled in Group 6 and will be dosed open-label. Since this is a first in human, phase I study, a sentinel cohort will be utilized. The first two subjects (1st sentinel group) one at each clinical site will be randomized to Group 2 or 3 and vaccinated with MVA-BN-YF with or without Montanide ISA 720 adjuvant (ISA 720). Subjects and study personnel will be blinded as to whether ISA 720 was administered. The primary objectives are the: 1) assessment of the safety, tolerability, and reactogenicity of MVA-BN-YF vaccine administered with or without ISA 720; 2) comparison of the safety, tolerability, and reactogenicity of MVA-BN-YF vaccine administered with or without ISA 720 with Yellow Fever Vaccine (YF-VAX) and MVA-BN.
The purpose of this study is to assess the immunogenicity, safety, and reactogenicity of the SB257049 candidate malaria vaccine when co-administered with Vitamin A, measles, rubella and yellow fever vaccines to children aged 6 months at the first vaccination.
To evaluate the immune status of yellow fever in adults with a history of two or more doses of vaccine, having received the second dose for at least 1 year, compared to re-vaccinated individuals (second dose) after 30 days.
Epidemic viral diseases have become more prevalent in recent years. Among the various strategies to prevent such epidemics, vaccination is the most cost-effective. However, populations that are immunized are typically already exposed to multiple previous vaccinations or natural infections. Studies from this and other laboratories have revealed that pre-existing dengue antibodies can either inhibit or enhance subsequent dengue infection depending on the pre-existing antibody levels. While cross-reactive antibody is potentially pathogenic in dengue, how it impacts immune response to vaccination is unclear. Indeed, aggregated at the site of vaccination and the respective draining lymph nodes are antigen-presenting and immune regulatory cells that express Fc receptors and play pivotal roles in determining the magnitude and polarity of the immune response. Vaccine uptake by these antigen-presenting cells may thus be either inhibited or enhanced when vaccines are opsonized with cross-reactive antibodies. In view of the limited knowledge on how cross-reactive antibodies affect vaccination outcome, investigators propose here a study that exploits the known cross reactivity between Japanese encephalitis (JE) virus antibody and yellow fever (YF) vaccine. Investigators hypothesize that cross-reactive antibodies impacts antibody response to YF at the point vaccination in a concentration-dependent manner by altering both vaccine uptake and the innate immune response by antigen presenting cells. Investigators will structure an open label clinical trial on sequential vaccination with JE and YF vaccines, with different time intervals between vaccinations. This would test immune response to YF vaccination in subjects with different titer of cross-reactive JE vaccine-derived antibodies.
It is thought that vaccines trigger innate inflammatory responses to induce antigenspecific adaptive immunity (the desired effect), but excessive inflammation may lead to serious inflammatory complications or unwanted side effects. Currently there is a lack of reliable biomarkers (a measurable biological response that predicts something) able to predict severe inflammation and this has resulted in the development of several vaccines being terminated and the withdrawal of some licensed vaccines which were associated with inflammatory complications. This study is part of the BIOVACSAFE project which is a 5year €30M project funded by the Innovative Medicine Initiative. The project involves a series of clinical studies using licensed vaccines as benchmarks to generate clinical data on inflammation and identify biomarkers that can be used to predict acceptable reactogenicity. The target is to identify biomarkers that can predict the occurrence of beneficial and detrimental effects in response to a vaccine. Such biomarkers could be used in future vaccine development programs to optimize selection of vaccine candidates with a profile that will be unlikely to generate worrisome safety signals once they are in generalized use. This study is one in a series of "training" studies which will each use different licensed vaccines that are prototypical representatives of a class of vaccine used in a particular target population. Forty eight subjects will be randomised into three groups to receive: A) Varicella zoster vaccine (n = 20), B) Yellow Fever vaccine (n = 20), C) Saline placebo (n = 8). Following a screening visit, participants will undergo a seven day residential visit which will include immunization and intensive monitoring of physiological (e.g. heart rate, oral temperature, blood pressure) metabolic and immune (innate and adaptive) parameters. This visit will be followed up by four outpatient visits with further monitoring and blood samples.