Humoral and Cellular Immune Responses of People Living With Human Immunodeficiency Virus After 3 Doses of Messenger RNA BNT162b2 Severe Acute Respiratory Syndrome Coronavirus 2 Vaccine: A Prospective Cohort Study

Background. Recent studies have shown good serological and cellular immune responses in people living with human immunodeficiency virus (PLWH) after receipt of 2 doses of messenger RNAA (mRNA) severe acute respiratory syndrome coronavirus 2 vaccine. Data are missing regarding the response after 3 vaccine doses. Methods. We followed up a group of PLWH who received 3 doses of the mRNA BNT162b2 vaccine and for whom data of humoral immune response after 2 vaccine doses were available. Patients provided a blood sample 4–6 months after the booster dose. The aim of the study was to measure the serological and cellular response after the third dose and to evaluate factors associated with the vaccine response. Results. Fifty patients have provided a serum sample for serological evaluation after the booster. The anti–receptor-binding domain (RBD) immunoglobulin (Ig) G titers were higher after the booster with a median delta of 3240 arbitrary units/mL. The median CD4⁺ T-cell count was 660/μL (interquartile range, 515–958/μL) and had no influence on the antibody level. Factors associated with lower delta included higher CD8⁺ T-cell count (P = .02) and longer time between the third dose and the blood test (P = .01). Higher anti-RBD IgG titer after the second vaccine (P = .03), as well as a longer interval between second and third doses (P = .031) were associated with higher delta. There was no increase in the median number of activated interferon γ⁺ and tumor necrosis factor α⁺ CD4⁺ T cells after the booster (n = 8). Conclusions. The anti-RBD IgG level after 3 doses of mRNA BNT162b2 vaccine was higher than the level after 2 doses, suggesting additional value of the booster. Cellular response did not further increase after a booster.