Therefore, we studied the effect of vaccinations on human CD4+ Treg responses, using a panel of four commonly used antiviral vaccines: a trivalent influenza vaccine (TIV) with and without the addition of adjuvant MF59® (Fluad® or Agrippal®), a HBV subunit vaccine (Engerix-B®) and a live attenuated yellow fever vaccine (Stamaril®). Here, CD4 is linked to influenza.