2521. Prevalence and Associated Factors of Protective Antibody Responses against Diphtheria, Tetanus, and Pertussis among HIV-Infected Thai Adolescents Stable on Combination Antiretroviral Treatment

Background To assess the prevalence and associated factors of protective antibodies against diphtheria, tetanus, and pertussis among HIV-infected adolescents stable on combination antiretroviral treatment (cART). Methods A multicenter seroprevalence study was conducted. Perinatally HIV-infected Thai adolescents (11–25 years) who had previous evidence of severely immune suppression (CD4 350 cells/mm3 for > 6 months or CD4 > 200 cells/mm3 with viral suppression [VS; HIV RNA 12 months) and had completed a 5-dose series of diphtheria, tetanus, whole cell pertussis (DTwP) vaccine during childhood were enrolled. Adolescents who received immunosuppressive agents or blood components within 6 months were excluded. Protective antibodies for diphtheria, tetanus, and pertussis were defined as diphtheria toxoid IgG ≥ 0.1 IU/mL, tetanus toxoid IgG ≥ 0.1 IU/mL, and anti-pertussis toxin IgG ≥ 5 IU/mL, respectively. Logistic regression analysis was performed to identify factors associated with protective antibody response to each antigen. Results Of 150 adolescents, 47% were male, a median age was 19 years. Forty (27%) and 0 (0%) adolescents had ever received tetanus, diphtheria (Td) or tetanus, diphtheria, acellular pertussis (Tdap) vaccine during adolescence, respectively. A median duration since the last dose of DTwP/Td vaccine was 12 years. At enrollment, 67% of adolescents were on NNRTI-based cART regimens, a median cART duration was 13 years. A median CD4 was 29%, and 90% had VS. Prevalence of protective antibodies against diphtheria, tetanus, and pertussis were 37%, 82%, and 52%, respectively. Proportion of adolescents with protective antibodies and geometric mean concentrations of antibodies to all antigens declined over time after the last immunization (Figures 1–3). Associated factors of protective antibodies to diphtheria, tetanus and pertussis are shown in Table 1. Conclusion Although having completed a 5-dose series of DTwP during childhood, significant proportion of our perinatally HIV-infected adolescents had no protective antibodies to those antigens, particularly diphtheria and pertussis, when entering adolescence. Tdap vaccination is a crucial strategy to prevent such diseases in the future. Disclosures All authors: No reported disclosures.