Prospective, non-equality, cohort study, where investigators propose to analyze humoral and cellular immunity after two doses of SARS-CoV-2 RNA vaccines in HIV-infected participants severely immunosuppressed.

A total of 92 HIV-infected subjects over 18 years old with ≤200 CD4/μl (experimental group; n=46) and ≥ 350 CD4/μl (as control group; n=46) who have completed two doses vaccination against SARS-CoV-2 will be included in the study.

Primary Objectives:

• To analyze the percentage of participants with SARS-CoV-2-specific IgG after 1, 6, and 12 months after vaccination in subjects with ≤200 vs ≥350 CD4/μL by electrochemiluminescence immunoassay (Elecsys® Anti-SARS-CoV-2. Roche Diagnostics).
• To analyze the percentage of subjects with specific T and memory B lymphocyte response against SARS-CoV-2 after 1, 6, and 12 months after vaccination with <200 vs ≥350 CD4/μL. Multiparametric flow cytometry in peripheral blood mononuclear cells (PBMCs) will be performed to detect the production of cytokines (IL-2, TNF-α and IFN-γ), cytolytic (perforin and granzyme B) and degranulation (CD107a) molecules from T cells, as well as to identify memory B cells specific to SARS-CoV-2 IgG+.

Secondary Objectives: To analyze in participants with <200 vs ≥350 CD4/μl after 1, 6, and 12 months after vaccination:

• Quantification of specific IgG titers against SARS-CoV-2
• The association of the T response to SARS-CoV-2 with humoral response parameters.
• The association of the T response against SARS-CoV-2 with other parameters of immune activation, inflammation and immunosenescence. The phenotypes of maturation (CD45RA and CD27), activation (HLA-DR and CD38), senescence (CD57+CD28-) and markers of immune exhaustion (TIGIT, LAG-3, TIM-3 and PD-1) in CD4 and CD8 lymphocytes T will be determined by multiparametric flow cytometry.

Inclusion Criteria:

1. HIV-infected subjects over 18 years old and ≤200 CD4/μl who have completed vaccination against SARS-CoV-2.
2. HIV-infected subjects with ≥350 CD4/μl who have completed vaccination against SARS-CoV-2 matched by age and sex as control group.
3. Sign the informed consent.

Exclusion Criteria:

1. Neoplastic or autoimmune disease known.
2. Treatment with steroids, immunomodulators, interferon, chemotherapy or any pathology that may impact immunological parameters after vaccination against SARS-CoV-2.
3. Active infections at the time of sampling.

The study was designed as a cohort study comparing the immune response after vaccination of HIV-infected subjects with the hypothesis that subjects with ≤200 CD4/μL will have a worse response than those with CD4 count ≥ 350/μL.