How should the MMR vaccine be administered to an adult patient weighing 210 lb?

The correct method for administering the MMR vaccine to an adult involves the use of the subcutaneous (SC) route. This is significant because MMR is a live attenuated vaccine, and administering it correctly is essential for its efficacy and the patient’s safety. For SC administration, the injection should be made in the outer aspect of the upper arm, typically the triceps area or the fatty tissue of the upper outer arm.

At a 90-degree angle, especially in a person who weighs 210 lb, there is a risk of injecting into muscle rather than the subcutaneous tissue, which could lead to complications or reduced effectiveness of the vaccine. A 45-degree angle for SC is appropriate for providing a sufficient depth for vaccine delivery while ensuring the vaccine remains in the subcutaneous tissue.

Choosing the right angle and site for injection avoids potential complications associated with intramuscular administration or improper depth of injection, which is critical for vaccines such as MMR that require SC delivery to ensure proper immune response.