This is a prospective, phase 3, multicenter, double-blind, randomized placebo-controlled study to investigate the efficacy, safety, and pharmacokinetics of repeat doses of IgPro20 in subjects with post SARS-CoV-2 infection 2019 postural orthostatic tachycardia syndrome). Eligible subjects will be randomized in a 2:1 ratio to receive subcutaneous (SC) infusions of IgPro20 …