Final answer:
The IM route, particularly using the anterolateral thigh muscle, is the preferred site for administering vaccines to a 7-month-old infant due to safety and the ample muscle mass presented by the site.
Step-by-step explanation:
The intramuscular (IM) route for administering vaccines to a 7-month-old is indeed preferred. The question seems incomplete, but if it pertains to the preferred site for the IM injections in infants, then the correct site would typically be the anterolateral thigh muscle. This site is recommended because it has less risk of injury to nerves and blood vessels, provides a large muscle mass, and is not as close to the major organs as other possible sites.
For infants and young children (from birth through 2 years of age), the vastus lateralis muscle in the anterolateral thigh is the preferred and safest muscle to receive the IM injection. As the child grows older, other sites such as the deltoid muscle may also be used, dependent on the muscle mass and development.