D.C. Mun. Regs. tit. 22, r. 22-B149
A student who has not received primary immunization shall receive three (3) doses of diphtheria-tetanus-containing vaccine. Beginning with the 2008/2009 school year, Tdap shall be used for one of the three (3) diphtheria-tetanus-containing vaccines in the series, preferably, the first dose. The first and second doses shall be administered not less than four (4) weeks apart. The third dose shall be administered not less than six (6) months after the second dose.
DTP, DT, DTaP, Td or Tdap doses administered before the age of eighteen (18) may satisfy § 148.1, unless administered before the appropriate age or at less than the required minimum interval between doses. If the last dose of diphtheria-tetanus-containing vaccine was given before four (4) years of age, an additional dose of Td/Tdap shall be administered not less than six (6) months after the previous dose. Beginning with the 2008/2009 school year, Tdap shall be used for one (1) dose.
A Td/Tdap diphtheria-tetanus-containing booster dose shall be administered at ten (10) years after the primary series or the last booster and by eleven (11) years of age. Beginning with the 2008/2009 school year, Tdap shall be used for one dose.
D.C. Mun. Regs. tit. 22, r. 22-B149