Evaluation of a single dose of diphtheria-tetanus toxoids among adults in Odessa, Ukraine, 1995: Immunogenicity and adverse reactions

Epidemic diphtheria spread to Ukraine in 1991, where it peaked in 1995 with >5000 reported cases, To refine epidemic control strategies, immunogenicit y of a tetanus-diphtheria toxoids vaccine (Td) containing 2 limits of flocc ulation (Lf) diphtheria toroid was evaluated. During a mass vaccination cam paign, adults at a clinic in Odessa received one dose of Td, At enrollment, 57.2% of 341 study participants had levels of diphtheria antitoxin (DAT) g reater than or equal to 0.1 IU/mL. Thirty and 180 days after receiving one dose of Td, 91.5% and 84.5% of the participants, respectively, had DAT leve ls greater than or equal to 0.1 IU/mL, However, among 40- to 49-year-old pa rticipants, only 78.8% and 73.8% had DAT levels greater than or equal to 0. 1 IU/mL at 30 and 180 days, respectively. This study suggests that one dose of 2 Lf diphtheria toroid is highly effective in raising DAT to protective levels in most adults; however, the study also shows that certain age grou ps, particularly persons 40-49 and, to a lesser degree, 30-39 years old may require additional doses or a complete three-dose primary vaccination seri es for optimal protection against diphtheria.