What is the usual route of administration for most vaccines?

Most vaccines are typically administered using the intramuscular (IM) or subcutaneous (SC) routes due to the efficacy and reliability of these delivery methods in eliciting a robust immune response.

Intramuscular injections allow the vaccine to be quickly absorbed into the bloodstream and stimulate a strong immune response, as they can inject the vaccine into a larger muscle mass where there is a rich blood supply. This method is commonly used for vaccines like influenza, hepatitis, and tetanus.

Subcutaneous injections, on the other hand, also provide a good route for vaccination, especially for some live attenuated vaccines and certain inactivated vaccines, as they can enhance the immunogenicity by allowing for the slower absorption of the vaccination components through lymphatic circulation.

While there are other routes such as oral or nasal sprays available for specific vaccines (such as the live attenuated influenza vaccine), the majority of vaccines still rely on the IM and SC routes for the best balance of efficacy, safety, and practicality in a clinical setting. Therefore, the correct response highlights the most prevalent and standard practice in vaccine administration.