Pre-existing systemic and nasal antibodies against avian H5 influenza A viruses vary according to childhood imprinting.

Pre-existing systemic and nasal antibodies against avian H5 influenza A viruses vary by birth year and childhood imprinting, with those born before 1957 showing higher levels.

• Why it matters: Understanding how early life exposure influences pre-existing immunity to H5 IAV is crucial for assessing population susceptibility and improving pandemic preparedness strategies.
• What they did: The study analyzed HA-specific antibodies in individuals born between 1928 and 1999, measuring serum, nasal IgG, and IgA titers, and comparing these across different birth cohorts.
• The result: Individuals born prior to 1957 exhibited higher pre-existing serum antibodies to group 1 HA antigens and greater nasal IgG and IgA titers to H5, indicating that early life exposure shapes mucosal and systemic immunity.