Figure 1. Biphasic decline in SARS-CoV-2 antibody titers.
a) Study design. Seventy-three SARS-CoV-2 convalescent patients with mild disease (ages 21–69) were enrolled and blood was collected approximately 1 month, 4 months, and 7 months post onset of symptoms. Bone marrow aspirates were collected from eighteen of the participants 7 to 8 months after infection and from eleven healthy volunteers (ages 23–60) with no history of SARS-CoV-2 infection. b) Blood IgG titers against S (left) and influenza virus vaccine (right) measured by ELISA in convalescent patients (open circles) at the indicated time post onset of symptoms and controls (closed circles). Dotted line indicates limit of detection. Heavy lines represent modeled antibody decay kinetics for S titers 1–4 months (dashed line; decay rate −0.00595, P<0.001, t1/2=116.5 days) and 4–7 months (solid line; decay rate −0.00101, P=0.04, t1/2=686.3 days) post symptom onset and for influenza virus vaccine titers 1–7 months post symptom onset (decay rate 0.000455, P=0.33) estimated using a longitudinal linear mixed model approach (see Methods for details).