Fig. 3

Subgroup analyses. CI confidence interval, ICU intensive care unit, RR risk ratio. Subgroup analyses include only trials with at least one event in one arm (i.e. trials with zero events in both arms were excluded). Number of comparisons differ from number of trials as two trials had more than one comparison. We defined high-titer as S-protein receptor binding domain (RBD)-specific IgG antibody titer of 1:640 or higher, or serum neutralization titer of 1:40 or higher. For studies using the Ortho VITROS SARS-CoV-2 IgG test, which reports a signal-to-cutoff (S/C) value, we defined high titer as S/C > 12 (corresponding to the initial United States Food and Drug Administration emergency use authorization) as prespecified. We complemented the high-titer definition with additional information made available in the March 2021 version emergency use authorization, e.g., EUROIMMUN (ratio ≥ 3.5) and Abbott ARCHITECT (S/C ≥ 4.5)