Proteomic analysis of antigen-specific serum IgG repertoires from healthy adults vaccinated with either mRNA-1010 or Fluarix quadrivalent influenza vaccines. Serum IgG was characterized using Ig-Seq, an approach integrating immunoglobulin proteomics with B cell receptor sequencing to identify and quantify individual clonotypes comprising the A/H3-specific serological repertoire across multiple time points post-vaccination.