Immunogenicity of Yellow Fever Vaccine in a Pediatric Population Vaccinated at 12-23 Months of Age in Argentina

Northern Argentina is a risk area for yellow fever (YF). Recent studies have suggested that immunity wanes in children vaccinated between 9 and 23 months of age. In 2015, a collaborative study conducted by the Ministry of Health (MoH) of Argentina, the Pan American Health Organization (PAHO), and the US Centers for Disease Control and Prevention (CDC) assessed the immunogenicity and safety of co-administration of YF and MMR vaccines in a pediatric population at 12-13 months of age. A total of 741 children presenting for routine immunization at 12-13 months of age enrolled and completed the study. It is now four to seven years since this pediatric group received their YF vaccinations. This cohort is unique because their initial YF vaccination and immune response to the vaccine dose are well characterized. Contact information collected during the earlier study will be used to locate the children. If consent is obtained, a 5ml specimen of blood will be collected and shipped to the CDC's Arboviral Diseases Reference Laboratory (ADRL) in Fort Collins, CO for plaque reduction neutralization testing using a 50% cut-off (PRNT50) to detect YF virus-specific neutralizing antibodies. Children with neutralizing antibody titers that are higher than their baseline titer collected approximately 28 days following YF vaccination will have PRNTs done for cross-reacting flaviviruses.

Eligibility Criteria

Inclusion Criteria:Children enrolled in the 2015 study received one dose of YF vaccine and had documented seroconversion regardless of theHealthy child, determined by clinical historyAvailability to perform a single blood drawInformed consent signed by the parents.Exclusion Criteria:Children in the 2015 study received one dose of the Yellow Fever vaccine and had NO documented seroconversion.Children enrolled in the 2015 study received a dose of the Yellow Fever vaccine and had documented seroconversion but, for different reasons, received a booster (minimum interval of one month between doses).Children enrolled in the 2015 study received one dose of the Yellow Fever vaccine and had documented seroconversion but developed Yellow FeverChildren enrolled in the 2015 study received one dose of the Yellow Fever vaccine and had documented seroconversion but are participating in another clinical drug trial of a drug, vaccine, or medical deviceChildren enrolled in the 2015 study received a dose of the Yellow Fever vaccine and had documented seroconversion but, for various reasons, are immunocompromised:Weakened immune function, including HIV infection, primary immunodeficiencies, having received immunosuppressive doses of oral or injectable corticosteroids (or equivalent), having received immunomodulators or chemotherapeutic agents, disease of the thymus, Severe illness/fever (mild illness without fever is not an exclusion criteria)● Any condition that, in the judgment of study personnel, poses a risk to the health of the participant or interferes with the assessment of response to the vaccine

Source: ClinicalTrials.gov (NCT05644145). StuddyBuddy aggregates publicly available trial information.

Immunogenicity of Yellow Fever Vaccine in a Pediatric Population Vaccinated at 12-23 Months of Age in Argentina

Summary

Eligibility Criteria