Ordering TDAP Titers: Not Recommended in Clinical Practice
Serologic testing (titers) for TDAP immunity is not routinely recommended or necessary for clinical decision-making, as vaccination decisions should be based on documented vaccination history rather than antibody levels. 1
Why Titers Are Not Standard Practice
The ACIP guidelines do not recommend routine serologic testing for tetanus, diphtheria, or pertussis antibodies in most clinical scenarios. 1 The vaccination approach is based on documented doses and timing rather than measured immunity levels.
Limited Situations Where Serologic Testing May Be Considered
For patients with unknown or uncertain vaccination history:
- Serologic testing for tetanus and diphtheria antibodies may be considered to avoid unnecessary vaccination in adults who likely received prior immunization but cannot produce records 1
- If tetanus and diphtheria antitoxin levels are each ≥0.1 IU/mL, previous vaccination is presumed, and a single dose of Tdap is indicated 1
- This approach is optional and not required—providers can simply proceed with catch-up vaccination without testing 1
Specific laboratory orders if testing is pursued:
- Order: Anti-tetanus toxoid IgG antibody level 1
- Order: Anti-diphtheria toxoid IgG antibody level 1
- Protective threshold: ≥0.1 IU/mL for both antigens 1
Why Pertussis Titers Are Not Useful
There is no standardized, clinically validated serologic test for pertussis immunity that guides vaccination decisions. 1 Unlike tetanus and diphtheria, pertussis antibody testing is not recommended even in uncertain vaccination scenarios.
The Standard Approach: Vaccination Based on History
For patients with documented complete vaccination:
- No testing needed—follow routine booster schedules 1
- Tdap once if never received, then Td every 10 years 1
For patients with unknown/incomplete history:
- Assume no prior vaccination and administer catch-up series: one dose of Tdap, followed by Td ≥4 weeks later, then another Td 6-12 months after that 1
- Alternatively, consider serologic testing for tetanus and diphtheria only (not pertussis) to potentially reduce unnecessary doses 1
Common Pitfalls to Avoid
- Do not order pertussis titers—they are not standardized or clinically actionable 1
- Do not delay vaccination while waiting for titer results in most scenarios; vaccination is safe even if the patient was previously immunized 1
- Do not use titers for wound management decisions—these are based solely on vaccination timing (≥5 years for contaminated wounds, ≥10 years for clean wounds) 1
- Do not restart the vaccination series if doses are delayed; simply continue from where the patient left off 2
Special Consideration: Arthus Reaction History
If a patient had an Arthus reaction after previous tetanus vaccination and you need to verify tetanus immunity before deciding on wound management, you may obtain a serum tetanus antitoxin level. 1 If the level is >0.1 IU/mL, the patient is considered protected and tetanus toxoid can be deferred. 1