CD4 and COVID-19: A reduced model containing variables associated (p ≤ 0.05) with SARS-CoV-2 spike (trimer) total Ig titers in univariate or multivariable regression confirmed that CD4+ T cell count (<200 vs. ≥500, β = −0.400, p = 0.033), HIV viral load (≥200–<5000 vs. <200, β = −0.275, p < 0.001), and days between second vaccination date and serology sample collection date (β = −0.003, p < 0.001) significantly predicted SARS-CoV-2 spike (trimer) total Ig titers in PLWH who received two doses of a COVID-19 vaccine (Table 4).