D.C. Mun. Regs. tit. 22, r. 22-B133
The first dose of measles, mumps, and rubella (MMR) vaccine shall be administered no earlier than twelve (12) months of age and not later than sixteen (16) months of age.
The second dose of MMR shall be administered at four (4) years of age and by the fifth birthday, but no earlier than twenty-eight (28) days after the first dose. The Department recommends administration of the second dose at the next pediatric visit after the first dose, but no earlier than twenty-eight (28) days after the first dose.
If single antigen measles, mumps, and rubella vaccines are used, two (2) doses of each vaccine shall be administered, with a minimum interval of twenty-eight (28) days between dose (one) 1 and dose (two) 2. A dose of MMR, Varicella, one of the single-antigen measles, mumps, rubella, or any other live parenteral vaccines shall not be administered less than twenty-eight (28) days apart, unless administered on the same day.
D.C. Mun. Regs. tit. 22, r. 22-B133