What is the correct method for administering the Tdap vaccine to an adult weighing 185 lb?

The correct method for administering the Tdap vaccine to an adult involves using an intramuscular route at a 90-degree angle into the deltoid muscle. This approach is based on several key factors regarding vaccine administration and anatomical considerations.

Intramuscular injections are preferred for several vaccines, including Tdap, because they allow for proper absorption and storage of the vaccine within muscle tissue. The deltoid muscle is the recommended site because it is large enough to accommodate the injection volume and provides an accessible location that is relatively easy to visualize and palpate.

Administering the injection at a 90-degree angle ensures that the needle enters the muscle layer directly, minimizing the risk of hitting underlying structures such as blood vessels or nerves. Moreover, this angle promotes proper delivery of the vaccine into the muscle, enhancing the immune response.

Other methods, such as subcutaneous injections or injecting at less than a 90-degree angle, do not align with the recommended practices for administering Tdap to adults. Subcutaneous routes are typically reserved for certain vaccines that require it, and injecting at a 45-degree angle may not effectively deliver the vaccine into the muscle where it can elicit a strong immune response. Therefore, using an intramuscular method at a 90