Intranasal adenovirus type 5 influenza vaccination enhances milk antibody responses and passive transfer to neonatal ferrets
Newborns and infants are particularly vulnerable to influenza, largely due to the immaturity of their immune systems. As such, maternal immunization is a valuable strategy to enhance influenza-neutralizing antibodies in both blood and breast milk, ensuring optimal passive immunity transfer to the infant. In our pregnant and lactating ferret maternal-neonatal model, we evaluated antibody responses to an adenovirus type 5-vectored H1N1 hemagglutinin vaccine delivered enterically, intranasally, or intramuscularly. While all three routes elicited a robust antibody response compared to saline-treated controls, intranasal vaccination significantly increased influenza-specific antibodies in dam serum, upper respiratory tract secretions, and milk, and subsequent transfer to suckling kits. Our results suggest that intranasal immunization was the most effective route for inducing functional influenza-specific antibodies in both dam serum and milk, with efficient passive transfer to suckling kits. Leveraging mucosal immune induction may enhance maternal antibody responses, transfer to offspring, and downstream neonatal protection.