Vaccines are designed to be given by specific routes because the way they enter the body affects how the immune system responds. Rotavirus is taken by mouth, so it’s not given by injection. The others are delivered by injection. The inactivated poliovirus vaccine is administered by intramuscular injection, typically into the muscle of the thigh in infants or the deltoid in older children, which is why it fits the scenario of an intramuscular (and in some contexts subcutaneous) administration pattern. Pneumococcal vaccines are also injections, usually intramuscular, with subcutaneous administration possible for some products or in certain settings, but the vaccine here is best matched by the intramuscular route. In short, the intramuscular route is the standard for this vaccine, aligning with its usual administration practice.