Which vaccine is not part of the routine immunizations by age 6 months?

• A. Hib.
• B. IPV.
• C. DTaP.
• D. Measles, mumps, and rubella (MMR).

Answer: (D)

The main idea is understanding which vaccines are given in the first year of life versus those saved for later. By 6 months, the vaccines routinely given include Hib, IPV, and DTaP, which are scheduled in the early months of infancy. The measles, mumps, and rubella vaccine, however, is not given until after the first year. It’s typically given as the first MMR dose at 12–15 months, with a second dose later in early childhood. This delayed timing is because MMR is a live attenuated vaccine and the immune system responds best after the first year, when maternal antibodies have waned and safety considerations are optimized. So, the vaccine not part of routine immunizations by age 6 months is the one addressing measles, mumps, and rubella.