Clinical Study of Immunity Duration of Yellow Fever Vaccine in Military

Study Overview
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Brief Summary
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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.

Detailed Description
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This is an observational study in young adult males who received the first dose of the yellow fever vaccine in 2009 when they participated in the Dose-response study of the yellow fever vaccine 17DD produced by Bio-Manguinhos / Fiocruz.

Official Title
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Clinical Study of Immunity Duration of Yellow Fever Vaccine in Military, Participants of Dose-response Study of Yellow Fever Vaccine 17DD Produced by Bio-Manguinhos / Fiocruz in 2009

Conditions
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Yellow Fever Vaccine

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Participated in the Dose-response study of the yellow fever vaccine 17DD produced by Bio-Manguinhos / Fiocruz in 2009. Not been revaccinated during the Dose-response study of the yellow fever vaccine 17DD produced by Bio-Manguinhos / Fiocruz of 2009. Not having received another dose of the 17DD yellow fever vaccine after participating in the 2009 Bio-Manguinhos / Fiocruz 17DD yellow fever vaccine dose-response study. Provide name, address, telephone and other information so that you can contact if necessary. Ability to understand and sign the TCLE. Exclusion Criteria: Impossibility or refusal to collect blood

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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Male

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 |
| --- | --- | --- |
| Number of seropositivity participants to YF vaccine as assessed by PRNT. | To evaluate the seropositivity by the means of the neutralizing antibody dosage in the participants of the Dose-response study of the 17DD yellow fever vaccine produced by Bio-Manguinhos/Fiocruz realized in 2009 | 8 years after the 1 st dose of yellow fever vaccine | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Individual repertoire of immunoglobulins profile as assessed by the PEPperPRINT and phenotypic/functional anti-amaryl memory cell analyse. | To evaluate individual repertoire of immunoglobulins profile directed to amaryl epitopes by the PEPperPRINT (PEPperCHIP® Yellow Fever Virus Proteome Microarrays) Guidelines and to evaluate the phenotypic and funcional profile of anti-yellow memory cell in the participants of the Dose-response study of the 17DD yellow fever vaccine produced by Bio-Manguinhos/Fiocruz realized in 2009 | 8 years after the 1 st dose of yellow fever vaccine | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Immunity duration