Figure. Anti–SARS-CoV-2 Antibody Responses After a Single Dose of Vaccine in Health Care Workers.

After COVID-19 vaccination, plasma was drawn at 0, 7, and 14 days; IgG binding titers against spike trimer were measured by enzyme-linked immunosorbent assay and live virus neutralization was assessed at days 0 and 14. A, IgG spike trimer half-maximal titers. By 7 days and continuing through 14 days following vaccination, both groups of health care workers with prior infection (asymptomatic and symptomatic) who received a single vaccine dose developed higher peak IgG titers than the antibody (Ab)-negative group. B, Live virus neutralization ID₉₉ (the 99% inhibitory dose, the dilution at which 99% of cells were protected). At 14 days, both groups of health care workers with prior infection (asymptomatic and symptomatic) who received a single vaccine dose developed higher neutralization titers than the Ab-negative group. Horizontal black lines represent median values.