The combination of baseline IgA responses to the Wuhan strain and IgA responses to VOCs were significantly associated with infection risk at both timepoints, however, the association was stronger at the day 30 timepoint in fourth dose recipients (day 30 HR = 5.73, p = 0.009, interim time point: HR = 2.34, p = 0.051, (Fig. 5c). Here, CD79A is linked to infection.