Fig. 2

Semester start and end IgG serology for students with a confirmed positive viral test during the semester. A Line plots show trajectories of anti-N IgG index values from baseline to endpoint for students who had baseline negative serology and positive viral tests reported during the semester. The horizontal dotted line at index value of 1.4 indicates the threshold for positivity. B Number of days between positive viral test date and endpoint serology collection date, based on endpoint serology status as determined by the anti-N assay. The whiskers indicate range and boxes indicate median with interquartile range (seropositive and seronegative medians are not significant, ns, p = 0.17, Mann Whitney U Test). C Line plots show trajectories of anti-S IgG values (in arbitrary units/mL). The horizontal dotted line at 50 AU/mL indicates the threshold for positivity. Black dots represent two students who were seropositive at semester start but did not have confirmed positive viral tests until after serum collection. D Number of days between positive viral test date and endpoint serology collection date, based on endpoint serology status as determined by the anti-S assay as in B