Here, we have characterized the phenotype of the IFN-γ-producing lymphocytes in response to FHA in a cohort of acutely B. pertussis-infected infants and young adults, as well as in pertussis-vaccinated children, to determine whether CD8+ lymphocytes may play a significant role in B. pertussis-specific IFN-γ responses in infants, compared to older children and adults. Here, CD8A is linked to pertussis.