CD4 and COVID-19: After removing 9517 VACS patients, there was no association between history of COVID-19 and breakthrough risk (aHR, 0.80 [95% CI, 0.56-1.13]), and the associations of age, calendar period, and viral suppression were comparable with the main model; Ad26.COV2.S plus an additional dose was associated with reduced risk of breakthrough (vs 2 doses of BNT162: aHR, 0.19 [95% CI, 0.05-0.78]), and the association with a CD4 count of 500 or greater cells/mm3 (vs <200 cells/mm3) was null (aHR, 0.94 [95% CI, 0.53-1.65]).