Influenza Immunity in Children

Study Overview
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Brief Summary
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This study evaluates how different methods of early exposure to influenza (natural infection, live attenuated influenza vaccination, inactivated influenza vaccination) initially stimulate immunity and poise the immune system to respond to a future challenge with the inactivated influenza vaccine.

Detailed Description
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The proposed research addresses the fact that, despite high childhood morbidity from influenza and broad recommendations for vaccination, very little is known about how anti-influenza immunity is shaped by the method of initial exposure. The objective of this research is to understand how CD4 T cell and B cell responses are altered by the method of initial influenza priming, with the long-term goal of determining how a child's initial influenza encounter poises the immune system to respond to subsequent influenza challenges. The investigators central hypothesis is that differences in the mode of influenza antigen exposure in early childhood will generate long lasting, detectable changes in memory CD4 T cell and B cell specificity and function that influence the response to future influenza vaccinations and infections. This hypothesis will be tested by comparing 1) CD4 T cell and 2) antibody responses in cohorts of children initially exposed to influenza through either natural infection or inactivated or live attenuated vaccination. A combination of multiparameter assays will be used to determine the phenotype and functional potential of hemagglutinin (HA)- and nucleoprotein (NP)-specific CD4 T cells. The breadth and avidity of the neutralizing and non-neutralizing antibody responses and its distribution against head and stalk epitopes will also be evaluated. By determining how initial priming shapes the specificity and functional potential of the anti-influenza CD4 T cell and antibody responses, the investigators will gain the knowledge necessary to optimize current influenza vaccination strategies and develop novel influenza vaccines able to provide highly efficacious universal protection against both seasonal and potentially pandemic viral strains.

Official Title
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Understanding How the Initial Encounter With Influenza Virus Poises Children for Protective Immunity

Conditions
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Influenza

Intervention / Treatment
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* Biological: Seasonal IIV 0.25 mL dose
* Other: Natural influenza infection
* Biological: Seasonal IIV 0.5 mL dose


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age Between 6 and 12 months to participate in the vaccination arm of cohort 1 (cohort 1A) Between 3 and 12 months to participate in the natural infection arm of cohort 1 (cohort 1B) Between 13 and 35 months of age to participate in either the vaccination or natural infection arm of cohort 2 Between 36 months and 5 years of age to participate in either the vaccination or natural infection arm of cohort 3 Between 6 years and 8 years of age to participate in either the vaccination or natural infection arm of cohort 4 Gestational age of ≥37 weeks at birth Parent/guardian can provide informed consent Available for the duration of the study History of previous IIV administration ONLY for participation in the vaccination arm of cohorts 2, 3, or 4 Acute illness documented to be due to influenza virus ONLY for participation in the natural infection arms of cohorts 1-4 Exclusion Criteria: Immunosuppression as a result of an underlying illness or condition (including HIV or a primary immunodeficiency syndrome) Active neoplastic disease Use of potentially immunosuppressive medications currently or within the past year (including chemotherapeutic agents) or chronic (>2 weeks) use of oral or inhaled steroid therapy A diagnosis of asthma requiring chronic controller medication Previous administration of influenza vaccine in the current influenza season ONLY for subjects receiving an influenza vaccination Receipt of immunoglobulin or another blood product within the year prior to study enrollment An acute illness within the previous 3 days or temperature >38o on screening EXCEPT for participation in the natural infection arms of cohorts 1-4 A contraindication to influenza vaccination EXCEPT infants between 3 and 5 months presenting with natural influenza infection whose only contraindication is their current age

Ages Eligible for Study
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Minimum Age: 3 Months
Maximum Age: 8 Years

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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Design Details

Primary Purpose: Basic Science
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: 6-12 months Seasonal IIV<br>Children 6 - 12 months of age vaccinated with seasonal IIV | Biological: Seasonal IIV 0.25 mL dose<br>* Fluzone (Sanofi Pasteur) 0.25 mL administered intramuscularly to children between 6 and 35 months of age<br>* Other names: Inactivated influenza vaccine;|
| Experimental: 3-12 months natural infection<br>Children 3-12 months of age presenting with natural influenza infection | Other: Natural influenza infection<br>* Children enrolled on presentation to their primary care provider with a natural influenza infection<br>Biological: Seasonal IIV 0.5 mL dose<br>* Fluzone (Sanofi Pasteur) 0.25 mL administered intramuscularly to children between 6 and 35 months of age<br>* Other names: inactivated influenza vaccine;|
| Experimental: 13-35 months Seasonal IIV<br>Children 13-35 months of age vaccinated with seasonal IIV | Biological: Seasonal IIV 0.25 mL dose<br>* Fluzone (Sanofi Pasteur) 0.25 mL administered intramuscularly to children between 6 and 35 months of age<br>* Other names: Inactivated influenza vaccine;|
| Experimental: 13-35 months natural infection<br>Children 13-35 months of age presenting with natural influenza infection | Other: Natural influenza infection<br>* Children enrolled on presentation to their primary care provider with a natural influenza infection<br>Biological: Seasonal IIV 0.5 mL dose<br>* Fluzone (Sanofi Pasteur) 0.25 mL administered intramuscularly to children between 6 and 35 months of age<br>* Other names: inactivated influenza vaccine;|
| Experimental: 3-5 years Seasonal IIV<br>Children 3-5 years of age vaccinated with seasonal IIV | Biological: Seasonal IIV 0.5 mL dose<br>* Fluzone (Sanofi Pasteur) 0.25 mL administered intramuscularly to children between 6 and 35 months of age<br>* Other names: inactivated influenza vaccine;|
| Experimental: 3-5 years natural infection<br>Children 3-5 years of age presenting with natural influenza infection | Other: Natural influenza infection<br>* Children enrolled on presentation to their primary care provider with a natural influenza infection<br>Biological: Seasonal IIV 0.5 mL dose<br>* Fluzone (Sanofi Pasteur) 0.25 mL administered intramuscularly to children between 6 and 35 months of age<br>* Other names: inactivated influenza vaccine;|
| Experimental: 6-8 years Seasonal IIV<br>Children 6-8 years of age vaccinated with seasonal IIV | Biological: Seasonal IIV 0.5 mL dose<br>* Fluzone (Sanofi Pasteur) 0.25 mL administered intramuscularly to children between 6 and 35 months of age<br>* Other names: inactivated influenza vaccine;|
| Experimental: 6-8 years natural infection<br>Children 6-8 years of age presenting with natural influenza infection | Other: Natural influenza infection<br>* Children enrolled on presentation to their primary care provider with a natural influenza infection<br>Biological: Seasonal IIV 0.5 mL dose<br>* Fluzone (Sanofi Pasteur) 0.25 mL administered intramuscularly to children between 6 and 35 months of age<br>* Other names: inactivated influenza vaccine;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Mean Percent of IFNg+ CD69+ CD4 T Cells Between Acute (H3N2) Infected and Vaccinated Subjects | % H3- and nucleoprotein (NP)-specific CD4 T cells were measured using intracellular cytokine staining | Visit 2 (day 8-14 post enrollment) | 
| Mean Percent of IFNg+ CD69+ CD4 T Cells Between Acute (H3N2) Infected and Vaccinated Subjects | % H3- and nucleoprotein (NP)-specific CD4 T cells were measured using intracellular cytokine staining | Visit 3 (day 20-28 post enrollment) | 
| Mean Percent of IFNg+ CD69+ CD4 T Cells Between Acute (H3N2) Infected and Vaccinated Subjects | % H3- and nucleoprotein (NP)-specific CD4 T cells were measured using intracellular cytokine staining | Visit 4 (day of vaccination year 2) | 
| Mean Percent of IFNg+ CD69+ CD4 T Cells Between Acute (H3N2) Infected and Vaccinated Subjects | % H3 protein- and nucleoprotein (NP)-specific CD4 T cells were measured using intracellular cytokine staining | Visit 5 (day 8-14 post-vaccination year 2) | 
| Mean Percent of IFNg+ CD69+ CD4 T Cells Between Acute (H3N2) Infected and Vaccinated Subjects | % H3 Protein- and nucleoprotein (NP)-specific CD4 T cells were measured using intracellular cytokine staining | Visit 6 (day 20-28 post-vaccination year 2) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Mean Change in Percent of IFNg+ CD69+ CD4 T Cells Between Vaccinated Subjects in Different Age Subsets | CD4 T cell quantity and specificity will be measured using intracellular cytokine staining. We report here the mean change in percent of cells reactive to the influenza HA protein and H3 protein. | Baseline to day 24 study year 1 | 
| Mean Change in Percent of IFNg+ CD69+ CD4 T Cells Between Vaccinated Subjects in Different Age Subsets | CD4 T cell quantity and specificity will be measured using intracellular cytokine staining. We report here the mean change in percent of cells reactive to the influenza HA protein and H3 protein. | Baseline to day 24 study year 2 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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natural influenza infection, live attenuated influenza vaccination (LAIV), inactivated influenza vaccination (IIV), infants, children