IGHG3 and infection: The hybrid immunity generated from breakthrough infection and booster dosing supported earlier claims that hybrid immunity restricts IgG4 class-switching, enhances all isotypes, including IgG1 and IgG3, and promotes anti-N responses following infection [46,47] because IgG4 levels were shown to continue to rise six months after the second mRNA injection, indicating that there is minimal immune imprinting [48].