IGHG3 and COVID-19: Among those with prior COVID-19, IgG3 anti-Spike responses were more persistent: one of the 20 tested samples (5%) was positive at P1, increasing to 23.1% (3/13) at P2, 16.7% (3/18) at P3, and 17.6% (3/17) at P4 (Fig. 4B).