CD4 and COVID-19: Both CD4+ and CD8+ T cells have important roles in the viral immune response and are positively correlated with the antibody response to SARS-CoV-2.29,30 CD4+ T-cell function is needed for effective vaccine responses.27,31 The increased risk of severe COVID-19 breakthrough among PWH with lower CD4 cell counts is likely multifactorial and requires further investigation.