Similarly, an American study (Ovsyannikova et al., 2014) used the linear correlation methods to explore the association of leptin-related genes variants with the antibody response to influenza vaccine in 50–80-year-old Caucasians, and they found that PPARG rs17793951G minor allele was associated with the A/H1N1 HAI antibody titers. Here, PPARG is linked to influenza.