To further understand how obesity may impact antibody responses to influenza vaccination, we conducted an in-depth analysis of influenza-specific IgG and IgA antibody repertoires of 205 participants, 100 with healthy weights (HW group; body mass index [BMI] = 18.5 to 24.9 kg/m2) and 105 with obesity (obese group; BMI ≥ 30 kg/m2) prior to and 30 days after vaccination with a split-virus trivalent influenza vaccine, which was the first to include the A/H1N1 2009 (Cal09) pandemic strain (2010-2011). The gene discussed is CD79A; the disease is obesity due to melanocortin 4 receptor deficiency.