Final answer:
Vaccines are most commonly given by injection into the arm, although alternative delivery methods like oral, intranasal, and aerosol are being developed to improve efficacy and patient comfort.
Step-by-step explanation:
Vaccines are most commonly administered through injection, typically into the arm, as illustrated in figures associated with vaccine delivery. This method is favored in healthcare settings and is preferred when a drug is not absorbed well in the gastrointestinal (GI) tract. Injected vaccines stimulate the systemic immune system, eliciting humoral and cell-mediated immunity, but may not effectively prompt a mucosal response, which is important for pathogens that reside in mucosal compartments. Despite the common use of injections, various alternative vaccine delivery methods are being explored to enhance efficacy and patient experience.
Some vaccines, such as the polio and typhoid vaccines, can be administered orally, and there is also an intranasal influenza vaccine available. The measles and rubella vaccines are being adapted for aerosol delivery through inhalation devices. Future innovations may see vaccines delivered through transdermal patches with microneedles or by mucosal routes such as intranasal or aerosol sprays. These methods could mobilize both the mucosal and systemic immune responses and potentially improve patient participation by reducing the anxiety associated with injections.