Evaluation of Tetanus Immunity in People Living with HIV: Reassessment of the Booster Dose Schedule

The decrease in CD4 + T lymphocyte count in people living with HIV causes a weakening of the immune response developed against the vaccine. This study aims to determine tetanus antibody levels in people living with HIV and to evaluate the relationship between these levels and various parameters. It aims to characterize those who lack protective antibody levels despite documented vaccination within the recommended 10-year interval and to question the adequacy of the current booster dose timing. Tetanus antibody levels were measured in serum samples from people living with HIV followed at the Infectious Diseases Clinic, using the Clostridium tetani toxin IgG (VIRCLIA; Vircell, Spain) kit by chemiluminescence immunoassay and interpreted according to the World Health Organization recommendations. All participants had a documented tetanus toxoid dose within the preceding 10 years, verified through the national Vaccination Tracking System. The study included 100 people living with HIV (88 men, 12 women; ages 20–73 years, mean = 38.04). Only age ( p < .001) and time since last vaccination ( p = .004) had a statistically significant effect on tetanus antibody levels. For protective levels (≥0.20 IU/mL), only age was significant ( p = .008), with higher protective levels in the 20–39 age group than in those over 40. Despite vaccination within the preceding 10 years, 17% ( n = 17) lacked protective antibody levels: 7.9% of those aged 20–39 versus 32.4% of those aged ≥40 (odds ratio = 5.57, 95% confidence interval: 1.77–17.48), and 25.0% of those vaccinated 5–10 years earlier versus 11.7% of those vaccinated within the previous 5 years. HIV-related clinical and immunological parameters were not significantly associated with tetanus antibody levels. Nevertheless, nearly one in five people living with HIV considered up-to-date lacked protective antibody levels, predominantly those aged ≥40 years. In this group, serological testing or a booster dose earlier than the recommended 10-year interval may be warranted.