From crisis to clarity Maternal vaccination during lactation and milk antibody dynamics

Human milk serves as a dynamic immunological bridge that adapts to maternal immunological experience, transferring passive immunity to protect infants against infectious diseases during the first months of life. In this thesis we investigated the impact of COVID-19 vaccination on this immunological relationship, specifically characterizing the temporal dynamics, magnitude, and persistence of SARS-CoV-2-specific IgA and IgG antibodies in human milk. In addition, we demonstrated distinct immunogenicity profiles by comparing antibody responses across different vaccine types, such as mRNA-based versus adenovirus-vectored vaccines, and examined how various immunization routes and vaccination strategies, such as natural infection and heterologous schedules, shape milk antibody profiles. Moreover, we synthesized available evidence on the safety and efficacy of maternal vaccination during lactation against a broad range of pathogens, establishing a framework to inform clinical decision-making and future vaccination strategies.