MMR at the 9-month visit
Under the National Immunization Program (NIP), the measles, mumps, and rubella (MMR) vaccine is given in two doses, at 9 months and 12 months of age. Each dose is 0.5 mL given subcutaneously in the upper arm. MMR is a live attenuated viral vaccine given by the subcutaneous route, and this is the detail that separates it from the other infant injections.
Why the subcutaneous route
Live attenuated vaccines such as MMR replicate after deposit in the subcutaneous tissue and produce a strong immune response with few local reactions. Many inactivated vaccines, such as the pentavalent vaccine and the pneumococcal conjugate vaccine (PCV), are given intramuscularly, which reduces local reactions to their components. The anterolateral thigh is the preferred intramuscular site in infants because the vastus lateralis is well developed at this age, while the deltoid is still small. The upper arm is used for MMR because the subcutaneous tissue there is easy to pinch up and the site is well separated from the thigh injections given at the same age.
| Vaccine | Dose | Route and site |
|---|
| BCG | 0.05 mL | Intradermal, upper arm |
| Pentavalent, PCV, IPV | 0.5 mL | Intramuscular, anterolateral thigh |
| MMR | 0.5 mL | Subcutaneous, upper arm |
How the distractors were built
Each wrong option is the correct technique for a different vaccine or a mix of two. 0.5 mL intramuscularly in the anterolateral thigh is how the nurse gives pentavalent vaccine and PCV, not MMR. 0.05 mL intradermally in the upper arm is the dose and route of BCG given at birth. 0.5 mL intramuscularly in the deltoid combines the right dose with the wrong route and an unsuitable infant site: MMR is not intramuscular, and the intramuscular infant vaccines of the NIP are given in the thigh, not the deltoid. Watch out! Questions on vaccine technique often offer the correct dose with the wrong route, so check route, site, and dose together.
Exam takeaway
Remember MMR as 0.5 mL, subcutaneous, upper arm, at 9 and 12 months. After giving it, the nurse records the dose in the child's immunization record and the target client list, schedules the second dose at 12 months, and advises the mother about common mild reactions such as fever. Keeping the vaccine in the cold chain and reconstituting it only with the diluent supplied are also part of correct administration.