[Should Tetanus Vaccine Booster be Given Earlier in Individuals Living with HIV?]

The incidence rate of tetanus has dramatically decreased following the discovery of the tetanus vaccine. A decennial booster dose is necessary to maintain the protective antibody levels after the primary vaccination schedule. The recommendations for the tetanus booster doses in adult "people living with acquired immune deficiency virus (HIV)" (PLWH) is similar to those for the general population. However, the duration of protective antibodies in PLWH is unknown. The aim of this study was to determine the factors affecting the response of HIV-infected individuals to tetanus vaccine and to evaluate the role of tetanus antitoxin level in determining the timing of the booster dose. PLWH attending the Adult Vaccination Unit of Ege University Faculty of Medicine Infectious Diseases and Clinical Microbiology Department were tested for tetanus antibodies from 30 October to 30 November 2020. Demographic information and the history of primary vaccination and booster doses were derived from medical files. Tetanus antibodies were detected with "enzyme immunoassay (EIA)" method with Clostridium tetani toxin 5S IgG-"enzyme linked immunosorbent assay (ELISA)" kit (Nova Lisa, Novatec Immundiagnostica, Germany). Antibody levels <0.01 IU/ml were considered negative, 0.01-0.5 IU/ml weak positive, 0.51-1.0 IU/ml positive and > 1.1 IU/ml strong positive. A level ≥ 0.50 IU/ml was considered as protective. The study included 146 PLWH [men (n= 126) and women (n= 40)]. The mean age was 39.5 ± 11.20 years (range: 18-65). Protective antibody level was detected in 114 (78.1%) participants. Receiver operating characteristics (ROC) analysis revealed that the ideal lower limit of CD4+ T cell count during booster vaccination for a person to develop protective antibody level was calculated as ≥ 218 cell/mm3. In the multivariate analysis, it was found that age <50 years (OR= 16.4, 95% CI= 4.9-55.2), the absence of AIDS at the time of diagnosis (OR= 6.7, 95% Cl= 1.05-17.4) and CD4+ T cell count ≥ 218 cells/mm3 at the time of vaccination (OR= 4.2, 95% CI= 1.05-17.4) were associated with protective levels of antibody. Protective levels of tetanus antibodies in PLWH are lower than the general population. It should be considered that the booster dose may be required earlier, especially in PLWH who are > 50 years old, with CD4+ T lymphocyte count <200 cells/mm3 during previous booster vaccination and who had AIDS at the time of the diagnosis.