In CHU Saint-Pierre, an additional cohort of patients infected vertically with HIV will be selected and will participate to the studyĭiagnostic Test: Yellow fever neutralizing antibodies measure.Whenever possible, an additional sera or plasma sample from the year before YF vaccine will be selected and analyzed to assess seroconversion rate.Whenever possible, an additional sera or plasma sample from the year following YF vaccine will be selected and analyzed to assess early seroconversion rate.Informed consent signed prior to any study procedure Exclusion criteria Inability to give informed consent Immunization with at least one injection of YF vaccine (Stamaril®,17D strain Rockefeller, Sanofi Pasteur) with proof of vaccine administration 3.

Infection with HIV-1 (vertical transmission or not) 2.

Risk factors (demographics and immunovirological parameters, antiretroviral treatment) of late waning (after 10 years) of YF NT Eligibility Inclusion criteriaġ.

Risk factors (demographics and immunovirological parameters, antiretroviral treatment) of early waning (before 10 years) of YF NT.

Risk factors (demographics and immunovirological parameters, antiretroviral treatment) for absence of seroconversion in the year following YF immunization.

Number of patients with protective YF NT ≥ 1:10 in the year following YF immunization.

data about patient's HIV history has to be extracted from the HIV database or from patients' fileĮstimated 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.

This sample must have been taken during the year following YF immunization.

whenever possible, an additional serum / plasma sample coming from serabank / plasmabank will be identified for each patient.

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.

The maximum duration of the study for each patient will be 1 visit, consisting of:

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.To compare persistence of NT in HIV patients infected vertically or not vertically.To identify risk factors for absence of seroconversion in the year after YF immunization.To modelize kinetics of NT after YF immunization in different subpopulations of HIV patients, including population of young HIV patients infected vertically.To identify risk factors for early and late waning of NT after YF immunization.To assess presence / persistence of Neutralizing Titers (NT) of antibodies after YF immunization in HIV-infected 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.

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. 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'. Why Should I Register and Submit Results?.

The persistence of yellow