View clinical trials related to Yellow Fever Vaccine.
Filter by: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.
Participating countries: Belgium Context: In June 2013, WHO notified that "a single dose of YF vaccine is sufficient to confer sustained life-long protective immunity against YF disease and that a booster dose is not necessary". . For HIV infected persons the recommendation was less stringent and the position paper concluded that hiv infected persons may "hypothetically, benefit from a second dose or booster dose ".1 Recently, WHO changed the recommendations about a booster dose of YF vaccine, based on the fact that serum neutralizing antibodies against YF are still at detectable levels after 20-35 years and probably lifelong in immunocompetent patients. Unfortunately, data on persistence of Neutralizing antibodies Titers (NT) in immunocompromised patients are missing and only few studies reported data about HIV-infected patients. Additional data are needed. Primary objective: To assess presence / persistence of Neutralizing Titers (NT) of antibodies after YF immunization in HIV-infected patients. Secondary objectives: 1. To identify risk factors for early and late waning of NT after YF immunization 2. To modelize kinetics of NT after YF immunization in different subpopulations of HIV patients, including population of young HIV patients infected vertically 3. To identify risk factors for absence of seroconversion in the year after YF immunization 4. To compare persistence of NT in HIV patients infected vertically or not vertically 5. To quantify seroconversion rate after YF vaccination Methodology / study design This study is a single arm, non randomized, cross-sectional, multicenter study in AIDS Reference Centers from Belgium. The maximum duration of the study for each patient will be 1 visit, consisting of: - the screening and inclusion visit (single visit V1) to check the patient eligibility, sign informed consent, perform the biologic tests necessary for the study and answer the questionnaire - whenever possible, an additional serum / plasma sample coming from serabank / plasmabank will be identified for each patient. This sample must have been taken during the year following YF immunization. - data about patient's HIV history has to be extracted from the HIV database or from patients' file Estimated enrolment 750 patients + 30 patients infected vertically with HIV Primary outcome Number of HIV patients with protective YF NT ≥ 1:10 at different timepoints after YF immunization Secondary outcomes 1. Number of patients with protective YF NT ≥ 1:10 in the year following YF immunization 2. Risk factors (demographics and immunovirological parameters, antiretroviral treatment) for absence of seroconversion in the year following YF immunization 3. Risk factors (demographics and immunovirological parameters, antiretroviral treatment) of early waning (before 10 years) of YF NT 4. Risk factors (demographics and immunovirological parameters, antiretroviral treatment) of late waning (after 10 years) of YF NT Eligibility Inclusion criteria 1. Infection with HIV-1 (vertical transmission or not) 2. Immunization with at least one injection of YF vaccine (Stamaril®,17D strain Rockefeller, Sanofi Pasteur) with proof of vaccine administration 3. Informed consent signed prior to any study procedure Exclusion criteria Inability to give informed consent Substudies - Whenever possible, an additional sera or plasma sample from the year following YF vaccine will be selected and analyzed to assess early seroconversion rate - Whenever possible, an additional sera or plasma sample from the year before YF vaccine will be selected and analyzed to assess seroconversion rate - In CHU Saint-Pierre, an additional cohort of patients infected vertically with HIV will be selected and will participate to the study
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
The study main objective is to assess the immune status of children and adults who have never vaccinated, they will receive the first dose of 17DD yellow fever vaccine provided by the study and will be monitored for 10 years. Depending on the results of the analyzed of the data, the period of monitoring may be extended.
The objective of this study is to study immune memory generated against the yellow fever (YFV) vaccine in participants who have previously received the vaccine. Volunteers will not receive vaccine shots; only immune responses to previous yellow fever vaccination will be studied. The study involves one or multiple blood draws.