People with HIV (PWH) often have a suboptimal response to vaccines, raising concerns regarding the efficacy of coronavirus disease 2019 (COVID-19) vaccines in this population. We aimed to evaluate the humoral immune response to the B.1 lineage and Omicron variant in PWH on antiretroviral therapy (ART) following COVID-19 vaccination. : We conducted a prospective study of 19 PWH on ART who received a two-dose series of the COVID-19 mRNA vaccine and a booster six months later. Participants without HIV infection (n = 25) were included as a healthy control (HC) group. The humoral response to the COVID-19 vaccine (anti-SARS-CoV-2 S IgG levels and ability to block ACE2-S interaction) against both the original B.1 lineage and the Omicron variant was assessed using immunoassays. : The humoral response in PWH was very strong (geometric mean fold rise, GMFR > 8) after the second dose and strong (GMFR > 4) after the booster dose for both the B.1 lineage and the Omicron variant. We found comparable humoral responses to the B.1 lineage and Omicron variant between PWH and HC groups after the second and booster doses (q-value > 0.05). The COVID-19 vaccine generated a significantly weaker humoral response against the Omicron variant compared to the B.1 lineage in both groups (q-value < 0.05). However, this response improved after the booster dose, although it remained weaker in PWH. : PWH showed a strong humoral response to the COVID-19 vaccine against B.1 and Omicron, though the Omicron response was weaker than B.1. Booster doses in PWH improved the Omicron response, but it stayed lower than B.1. Findings confirm vaccine effectiveness in PWH, stressing the critical role of boosters and potential need for updated vaccines for variants like Omicron.