Which statement best describes why parenteral vaccines may use a smaller dose than oral forms?

Which statement best describes why parenteral vaccines may use a smaller dose than oral forms?

• A. They are cheaper
• B. They require refrigeration
• C. The vaccine is not affected by the GI tract so a smaller dose will achieve the same therapeutic effect
• D. They require no special storage

Answer: (C)

Delivering vaccines by injection bypasses the digestive system, so the antigen reaches the immune system more efficiently. Oral vaccines must survive stomach acid and digestive enzymes and then be absorbed through the gut lining, where they can be degraded or poorly delivered to immune cells. Because parenteral administration sends the antigen directly to tissues rich in antigen-presenting cells, a smaller amount can trigger a strong enough immune response. Storage or cost factors don’t explain the dose difference, whereas bypassing the GI tract and the resulting greater efficiency of immune activation do.

Delivering vaccines by injection bypasses the digestive system, so the antigen reaches the immune system more efficiently. Oral vaccines must survive stomach acid and digestive enzymes and then be absorbed through the gut lining, where they can be degraded or poorly delivered to immune cells. Because parenteral administration sends the antigen directly to tissues rich in antigen-presenting cells, a smaller amount can trigger a strong enough immune response. Storage or cost factors don’t explain the dose difference, whereas bypassing the GI tract and the resulting greater efficiency of immune activation do.