What is the difference between Tdap (Tetanus, diphtheria, and pertussis) and DTaP (Diphtheria, Tetanus, and pertussis) vaccines?

Differences Between Tdap and DTaP Vaccines

The main difference between Tdap and DTaP vaccines is that DTaP is used for primary vaccination in children under 7 years, while Tdap is a reduced-antigen booster formulation for adolescents and adults. 1

Key Differences

• Age Indications:

  • DTaP: For children aged 6 weeks through 6 years 1
  • Tdap: For adolescents and adults (Boostrix for ages ≥10 years; Adacel for ages 10-64 years) 1

• Antigen Content:

  • DTaP: Contains higher quantities of diphtheria toxoid and pertussis antigens 1
  • Tdap: Contains reduced quantities (10-50%) of all toxoids and antigens to minimize reactogenicity in older individuals 2

• Formulation Purpose:

  • DTaP: Primary vaccination series (5 doses) for infants and young children 1
  • Tdap: Single booster dose for adolescents and adults who have completed their primary DTaP/DTP series 1

Antigen Content Comparison

The following table shows the difference in antigen content between DTaP and Tdap vaccines 1:

Antigens	DTaP (Infanrix)	Tdap (Boostrix)	DTaP (Daptacel)	Tdap (Adacel)
Tetanus toxoid (Lf)	10	5	5	5
Diphtheria toxoid (Lf)	25	2.5	15	2
Pertussis toxoid (μg)	25	8	10	2.5
FHA (μg)	25	8	5	5
Pertactin (μg)	8	2.5	3	3
Fimbriae 2+3 (μg)	-	-	5	5

Clinical Applications

• Primary Vaccination:

  • DTaP is administered as a 5-dose series at ages 2,4,6,15-18 months, and 4-6 years 1
  • DTaP should never be used in individuals ≥7 years of age 1

• Booster Vaccination:

  • Tdap is recommended as a single booster dose for adolescents at age 11-12 years 1
  • Tdap is recommended for adults who have not previously received it 1
  • Tdap is recommended during each pregnancy, preferably at 27-36 weeks gestation 1

Important Clinical Considerations

• Inadvertent Administration:

  • If DTaP is inadvertently given to someone ≥7 years, it should count as the Tdap dose 1
  • If Tdap is inadvertently given as one of the first 3 doses in the infant series, it should not be counted as valid and should be replaced with DTaP 1
  • If Tdap is given as the 4th or 5th dose in the infant series, it can be counted as valid 1

• Safety Profile:

  • Both vaccines have similar safety profiles when used as indicated for their respective age groups 2, 3
  • Local reactions (pain, redness, swelling) are the most common adverse events for both vaccines 2, 4
  • DTaP used in adults (off-label) has shown higher reactogenicity compared to Tdap 4

• Immunogenicity:

  • Both vaccines effectively induce protective antibody levels against diphtheria, tetanus, and pertussis 2, 3
  • Tdap produces robust immune responses in adolescents and adults despite containing reduced antigen amounts 3, 5

Common Pitfalls to Avoid

• Do not use DTaP in individuals ≥7 years due to increased risk of local reactions 1
• Do not miss opportunities to administer Tdap to eligible adolescents and adults, especially those who will have contact with infants 1
• Do not confuse packaging of adult Tdap, pediatric DTaP, and other vaccines, as they may appear similar 1
• Do not administer additional doses of Tdap except during pregnancy, as it's not licensed for routine boosting (use Td for subsequent boosters) 1

By understanding these differences, clinicians can ensure appropriate vaccine selection based on patient age and vaccination history, maximizing protection against these serious diseases while minimizing adverse reactions.