Please clarify on the minimum interval table in Appendix A of the Pink Book, the minimum interval between DTaP #3 and DTaP #4. Is it 6 months or 4 months?
This refers to “Recommended and Minimum Ages and Intervals Between Vaccine Doses” (which also appears in the ACIP “General Recommendations”). This table says there is a 6 month interval between the 3rd and 4th doses and the minimum age for the 4th dose is 12 months of age. However, the 5th footnote (**) says that a 4th dose given >4 months after the 3rd dose needn’t be repeated. The issue is when should you schedule the 4th dose vs. when can you count a 4th dose as valid after it has been given. Ideally, the 4th dose should be scheduled 6 to 12 months after the 3rd dose, which is the RECOMMENDED interval, and it should always be given after the 1st birthday. However, a few years ago we ran into a situation where some children had gotten the 4th DTaP sooner than 6 months after the 3rd dose. We took this issue to the ACIP. The committee felt the benefit of revaccinating those children was not worth the risk of local reactions from having too many DTaP close together. Therefore, if on a r