IgG3, C1q fixation, and opsonic-phagocytosis seropositivity were associated with a faster PC1⁄2 (range of the mean reduction in PC1⁄2, 0.47–1.16 hours; P range, .001–.03) and a reduced odds of having a PC1⁄2 of ≥5 hours and having parasitemia 3 days after treatment. Here, IGHG3 is linked to parasitic infectious disease.