Active clinical trials for "Yellow Fever"

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

This study aims to investigate the effect of providing additional information about possible mild side effects of the yellow fever vaccination on the reporting of physical symptoms. Additionally, the project aims to investigate the relationship between individual characteristics (trait anxiety and perceived sensitivity to medication) and the reporting of physical symptoms, as well as possible interactions between the level of information provided and individual characteristics. We hypothesize that more information about mild symptoms provided to participants will increase the number of reported symptoms after vaccination.

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.

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.

A randomized clinical trial comparing fractional dose Yellow Fever vaccination to the full dose among children aged 9-23 months in Uganda. Children will have immune response assessed at baseline, 4 weeks, and 12 months after vaccination. Enrolled participants will be randomized to one of three arms: A. One-fifth fractional dose (0.1 ml) administered subcutaneously B. One-half fractional dose (0.25 ml) administered subcutaneously C. Full dose (0.5 ml) administered subcutaneously

This is a passive enhance safety surveillance (ESS) of Stamaril® vaccine in Korea. The objective is to collect suspected related adverse events following vaccination with Stamaril® in routine practice.

In the recent past there has been a number of large urban Yellow Fever outbreaks in sub-Saharan Africa, tropical South Americas, The demand for Yellow Fever vaccines in response to the large urban outbreaks occurring concurrently and the risk of further spread through Africa and to Asia was larger than the available global supply. In this situation, the World Health Organisation (WHO) developed recommendations for the use of fractional doses of Yellow Fever vaccine as a dose-sparing strategy. These recommendations were based on data from a limited number of clinical trials, none of which had been conducted in Africa. This was due to the uncertainties on the minimum dose requirement. Our study complements a study which is comparing full standard dose to 1/5th of standard dose of all four WHO-prequalified YF vaccines in adults (ClinicalTrials.gov number: NCT02991495), and is currently ongoing at KEMRI CGMRC and Epicentre, Mbarara which is designed to answer questions on the use of current stock of YF vaccines with a potency as close as possible to each manufacturers' minimum release. Data from this trial will inform a WHO recommendation on using 1/5th of the current standard dose of vaccine for outbreak control. However, since many vials will contain excess YF vaccine such that 1/5th of a vial is likely to be substantially above the current minimum potency requirements, these data may not be scientifically explanatory regarding the minimum dose required for preventive use. The new complementary study, aims to determine the lowest YF vaccine dose that is non-inferior to the current standard full dose among populations in sub-Saharan Africa. The study will be conducted in Kenya (KEMRI Center for Geographical Medicine Research-Coast (CGMR-C), Kilifi) and Uganda (Epicentre, Mbarara) with trial participants recruited at both sites, using vaccine from one WHO-prequalified manufacturer (Institut Pasteur de Dakar, Senegal (IPD)).

The investigators at Rockefeller University are doing this research to study how the immune system responds to viruses and other infectious agents by using the yellow fever 17D vaccine as a model. The YFV-17D vaccine is one of the safest and most effective vaccines known and has been used to vaccinate humans against yellow fever virus (YFV) infection since the 1930s. By studying how the human immune system responds to the YFV vaccine we hope to learn more about the normal functioning of the immune system so that it might be possible to design new, more effective types of vaccines to prevent important infectious diseases. The reason for doing this research is: Currently there is very little information about which factors determine the effectiveness of the initial (primary) immune response to a foreign substance (antigen), such as a virus, that person may be exposed to. There is also very little known about what determines how effectively and for how long a person's immune system can react to the same antigen to prevent another infection. Studies in animals have given us important information about how the immune systems of other animals behave upon initial or repeated exposure to antigens,but these topics have not been studied in detail in humans. The following hypotheses will be tested: The magnitude of the initial expansion of T lymphocytes (the "clonal burst") specific for the infecting virus determines the level at which memory T cell responses are generated against the specific viral antigen and the duration of the memory T cell response generated in the body. The majority of CD8 T cells generated after immunization are yellow fever specific and not "bystander activation" of non-specific cells.

The immune system is composed of diverse cell types with different functions that act together in order to defend against infection. This pilot study will test a new technology for studying these many different cell types at very large numbers at the level of individual cells. This method will then be used to identify the cell types and functions important for the immune response to the highly protective yellow fever vaccine, which will improve our understanding of effective vaccine features.

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.