Data on vaccine efficacy and immunogenicity in PLWH remains limited (reviewed in13), and although there are some conflicting results, meta-analyses14 and recent studies15 have shown reduced levels of seroconversion and neutralization after a second dose of viral vector vaccine dose in PLWH receiving cART, with lower CD4 T cell count/viremia and older age resulting in a more impaired response and more rapid breakthrough infection.16 Here, CD4 is linked to infection.