1st gets brainliest- describe three specific aspects of vaccine technology and how they have prevent the flu

Insulin is a peptide therapeutic used to manage type 1 diabetes, which affects more than 20 million people worldwide according to the international diabetes federation. a significant limitation to the broad distribution and use of insulin to treat type 1 diabetes is the fact that it must be administered by injection rather than orally. why is insulin administered by injection and not orally?