Complementary Study of the Duration of Post-vaccination Against Yellow Fever Immunity in Children

Study Overview
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Brief Summary
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In a previous study by the researchers' group, the researchers' investigate the duration of yellow fever post-vaccination immunity in vaccinated children between 9 and 23 months of age. However, in this study, samples of children in the pre-vaccine period, also known as unvaccinated children samples (NV) have not been investigated. It is believed that to seek evidence about the immune status in the medium and long term after vaccination against yellow fever is necessary to investigate paired samples of children not vaccinated (NV), with re-evaluation 30-45 days after primary vaccination. The proposed study is to consolidate aspects of humoral (neutralizing antibodies) and cellular (phenotypic and functional parameters of T cells and memory B) by means of complementary longitudinal investigation children, 9-23 months old, unvaccinated (NV) and 30-45 days after primary vaccination.

Detailed Description
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A sample of 60 children aged 9 to 23 months paired in the pre-vaccine period (NV) and 30-45 post-primary vaccination days will be selected at health facilities in the metropolitan region of Belo Horizonte. Children whose mothers consent to participate in research, have collected blood and elements of past medical history recorded. Analyses of humoral and cellular biomarkers will be used in a comparative study with other post-vaccination periods previously analyzed in children during the first phase in study funded by the Ministry of Health. specific objectives: Estimate and compare the proportion of positivity and the geometric mean plasma titers of neutralizing antibodies against yellow fever; Assess lymphocyte frequency T and B memory induced in vitro by the vaccine antigen 17DD substrains, and... Quantify the lymphocytes T CD8 + producers of intracytoplasmic cytokines induced in vitro by the vaccine antigen 17DD substrains in unvaccinated children and primed aged between 9 and 23 months, categorized according to the vaccination time 30-45 days.

Official Title
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Complementary Study of the Duration of Post-vaccination Against Yellow Fever Immunity in Children

Conditions
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Yellow Fever

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Will be eligible for the study: children 9-23 months of age; both sexes; children who will be vaccinated against yellow fever, whose parents or guardians sign the consent form. Exclusion Criteria: children who received another vaccine within 30 days before or after the yellow fever vaccine; children which have permanent or temporary immunosuppression, including those treated with corticosteroids at doses higher than 2 mg / kg, and those with disease autoimmune diseases, transient or permanent immunosuppression induced diseases (cancer, AIDS, etc.) or treatment (immunosuppressive drugs, radiotherapy, etc.). Corticosteroids (such as prednisone, dexamethasone) for less than two weeks, or by inhalation or topical use, do not indicate exclusion from the study, but must be registered in the questionnaire (Annex II); children with hemoglobinopathies; children with a history of blood transfusion or treatment with hyperimmune serum up to 90 days prior to blood collection.

Ages Eligible for Study
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Minimum Age: 9 Months
Maximum Age: 23 Months

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Quantification of Humoral and cellular immunity after first yellow fever vaccination | Consolidating aspects of humoral (quantification of neutralizing antibodies - >2.log10IU/mL) and cellular (Percentege of phenotypic and functional parameters of T cells and B memory) through a complementary longitudinal investigation in children aged 9 to 23 month old unvaccinated and 30-45 days after first vaccination . | Time 0 (immediately before) and Time 1 (30-45 days after) primary vaccination against yellow fever | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Quantification of titers of neutralizing antibodies in plasma samples | Quantify the titers of neutralizing antibodies against yellow fever immediately before and 30-45 days after primary vaccination against yellow fever in children 9-23 months of age without yellow fever vaccination history. | Time 0 (immediately before) and Time 1 (30-45 days after) primary vaccination against yellow fever | 
| Evaluate the frequency (percentage) of T cells and B memory induced in vitro by the vaccine antigen 17DD | Evaluate the frequency (percentage) of T cells and B memory induced in vitro by the vaccine antigen 17DD immediately before and 30-45 days after primary vaccination against yellow fever in children 9-23 months old with no vaccination history against yellow fever. | Time 0 (immediately before) and Time 1 (30-45 days after) primary vaccination against yellow fever | 
| Evaluate the frequency (percentage) of T and B cells expressing intracytoplasmic cytokines in vitro induced by the vaccine antigen 17DD | Evaluate the frequency (percentage) of T and B cells expressing intracytoplasmic cytokines (gama interferon; IL-5, alfa-TNF) CD8 + T lymphocytes, in vitro induced by the vaccine antigen 17DD immediately before and 30-45 days after primary vaccination against yellow fever, in children 9-23 months of age without yellow fever vaccination history. | Time 0 (immediately before) and Time 1 (30-45 days after) primary vaccination against yellow fever | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Yellow Fever Vaccine, Immunity, Humoral, Immunity, Cellular, children