Figure 2. Timeline of antibody responses and SARS-CoV-2 infections among US healthcare worker participants in the Prospective Assessment of SARS-CoV-2 Seroconversion (PASS) study, January–August 2021 (17 unvaccinated and 227 vaccinated participants). Each horizontal bar represents the infection, vaccination, and serologic status obtained monthly in all participants who had not been diagnosed with SARS-CoV-2 by PCR or S protein IgG seroconversion by January 31, 2021. White spaces indicate no data. Gray bars represent negative S protein IgG. Red bars indicate month of SARS-CoV-2 diagnosis by PCR positivity or S protein IgG seroconversion. Yellow bars indicate S protein IgG seroconversion after SARS-CoV-2 diagnosis in unvaccinated persons, and orange bars indicate presence of both S protein and NP antibodies in unvaccinated persons. Light green bars indicate S protein IgG seroconversion after vaccination. Dark green bars indicate detection of NP IgG in addition to S protein antibodies at timepoints postvaccination. S, spike protein; NP, nucleocapsid protein; ICU, intensive care unit; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.