Ask the Experts - DT Vaccine Post-Diphtheria Disease
Is the DT vaccine indicated anymore after a diphtheria attack in a 10-year-old boy?

Dr. S. Ghargi

The Centers for Disease Control and Prevention and the American Academy of Pediatrics recommend diphtheria toxoid after infection, since infection does not necessarily confer immunity. Since the child is over age 7 years, Td should be used for immunization. Td has 2 Lf units of diphtheria toxoid compared with DT, which has 7-8 Lf diphtheria toxoid units. Td in older children, adolescents, and adults is less reactogenic than DT.

If the 10-year-old child had received no prior diphtheria toxoid immunization, then the first dose of Td should be followed by a second dose at 4 weeks or more and a third dose 6-12 months later or more to complete the 3-dose primary series. A Td booster should be administered every 10 years.

If the child has been incompletely immunized then the series should be completed according to the above schedule. There is no need to restart the series no matter how long the interval before the preceding dose(s). If the series has been completed, then only a booster is indicated.