CD4 and HIV infectious disease: We and others have previously shown a failure to mount a robust antibody response following COVID-19 vaccination in advanced HIV infection with low CD4 T cell counts below 200 cells/μl (Hassold et al., 2022; Nault et al., 2021; Noe et al., 2021; Spinelli et al., 2021; Touizer et al., 2021).