This is much longer than a previous observation of detectable IgA 6 months after infection, and may contribute to long-term protection.59 Antibody maturation is a relatively slow process that is supported by TFH cells in the GC.24 Our result show that spike-specific IgG antibody maturation peaked at 5 to 8 months after infection, while spike-specific IgG3 and IgA were fully mature at the 12 months. This evidence concerns the gene IGHG3 and infection.