When is the DTaP vaccine series given in infancy?

• A. At 2, 4, and 6 months, with boosters at 15–18 months and 4–6 years.
• B. At birth and 2 months.
• C. Only at 2 months.
• D. 6, 12, and 18 months.

Answer: (A)

The main idea is that protection from DTaP is built through a primary series started in early infancy and then sustained with later booster doses. The vaccine is given three times in infancy—at 2, 4, and 6 months—because multiple exposures are needed for the immune system to develop strong, lasting antibody protection. After completing the primary series, boosters are used to maintain immunity as antibody levels decline over time, specifically at 15–18 months and again at 4–6 years.

Starting at birth or only at 2 months wouldn’t provide the full primary series, and schedules like 6, 12, and 18 months miss the necessary early doses and the later boosters.