Learning Objectives for this Presentation:
By the end of the presentation participants will be able to understand the safety evidence for ACIP recommendations on intervals and administration sequence of DTCV: Td, tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap), and meningococcal conjugate (MCV4) vaccines.

Background:
Historically, unacceptable moderate/severe local adverse event (AE) rates were observed after adults received DTCV with high diphtheria toxoid content or at short/frequent intervals. ACIP considered available data to inform recommendations on safe interval and administration sequence for adolescent/adult DTCV: Td, Tdap and MCV4.

Objectives:
To review evidence for ACIP recommendations on Td-to-Tdap interval and administration sequence for Td/Tdap and MCV4.


Methods:
We reviewed prelicensure, postlicensure, and ongoing safety studies of Tdap, Td and MCV4.


Results:
Tdap-to-Td interval: Prelicensure adolescent/adult Tdap trials (N>6000) demonstrated safe Tdap use ≥5 years after Td/DTaP; persons who received a DTCV <5 years earlier were excluded. A Canadian study reported similar local AE rates in children/adolescents with a DTCV-to-Tdap interval of ~2 years (N=416) versus ≥10 years (N=678).
Administration of Td/Tdap and MCV4: No prelicensure concomitant vaccination studies of Tdap and MCV4 were conducted. In an adolescent trial, administering Td and MCV simultaneously (N=509) or Td first, then MCV4 1 month later (N=512) were acceptably safe practices.
Ongoing Studies: A safety survey of healthcare personnel (HCP) found similar local AE rates in HCP with a Td/TT-to-Tdap interval <2 years (N=370) versus ≥2 years (N=1792). Medically-attended severe local AEs in persons with various patterns of DTCV receipt are being assessed through CDC's Vaccine Safety Datalink.


Conclusions:
Evidence supports safety of ACIP suggested/encouraged Td-to-Tdap intervals of ≥5 years for adolescents and ≥2 years for selected adults. Some data support safety of shorter intervals and simultaneous administration of Tdap/Td and MCV4 when both vaccines are indicated and available. Additional data may inform future ACIP DTCV recommendations.