What is the protective efficacy of each dose of the Diphtheria, Tetanus, and Pertussis (DTaP) vaccine?

Protective Efficacy of DTaP Vaccine by Dose

The DTaP vaccine provides varying levels of protection with each dose, with a 3-dose primary series offering 79-89% efficacy against pertussis disease, while the full 5-dose series provides 88.7% overall effectiveness with protection peaking at 98.1% in the first year after the fifth dose. 1

Pertussis Protection by Dose

• A 3-dose primary series of DTaP administered at ages 2,4, and 6 months provides vaccine efficacy estimates ranging from 79% to 89% against culture-confirmed pertussis disease, with protection lasting up to 2 years after the third dose 1
• The complete 5-dose DTaP series has an estimated overall effectiveness of 88.7% (95% CI = 79.4%–93.8%) against pertussis 1
• Within the first year after receiving the fifth DTaP dose, vaccine effectiveness reaches its peak at 98.1% (95% CI = 96.1%–99.1%) 1
• Protection wanes over time, with effectiveness declining to approximately 71.2% (95% CI = 45.8%–84.8%) by ≥5 years after the fifth dose 1
• For every additional year after the last dose of DTaP, the odds of pertussis increase by 1.33 times (95% CI: 1.23-1.43) 2
• Assuming 85% vaccine efficacy initially, only about 10% of children vaccinated with DTaP would remain immune to pertussis 8.5 years after the last dose 2

Diphtheria Protection by Dose

• After receiving 3 doses of diphtheria toxoid-containing vaccines, virtually all infants develop protective diphtheria antitoxin titers >0.01 IU/mL 1
• A diphtheria antitoxin level of 0.01 to 0.09 IU/mL provides some degree of protection, whereas levels ≥0.1 IU/mL are considered fully protective 1
• Levels >1.0 IU/mL are associated with long-lasting protection against diphtheria 1
• After the primary vaccination series, protection lasts for approximately 3-5 years, requiring booster doses to maintain immunity 1
• The booster dose at age 4-6 years is crucial for maintaining protection throughout school-age years 1

Tetanus Protection by Dose

• One dose of tetanus toxoid vaccine provides little to no immunity 1
• After receiving 3 doses of tetanus toxoid-containing vaccine, virtually all infants and adults develop protective tetanus antitoxin titers >0.1 IU/mL 1
• A primary immunization series with 3 doses of tetanus toxoid induces a mean antitetanus level of 0.2 IU/mL, providing protection from tetanus for approximately 3-5 years 1
• Additional booster doses significantly heighten the immune response and prolong the duration of protective immunity 1
• Booster doses at age 4-8 years and during adolescence provide long-lasting protective immunity with protection lasting 20-30 years from the last dose 1
• Complete primary vaccination with tetanus toxoid provides protection for at least 10 years in most recipients 3

Immune Response to Individual Doses

• Immune responses following the first and second doses of DTaP have not been extensively measured in clinical studies 1
• After 4 doses of Daptacel (Sanofi Pasteur), 98.5% of children achieve diphtheria antitoxin levels of ≥1.0 IU/mL, and 100% achieve tetanus antitoxin levels of ≥1.0 IU/mL 1
• The fifth dose at age 4-6 years is expected to produce a robust immune response in children previously primed with the same vaccine 1
• Administration of DTaP at birth has been shown to be safe but results in significantly lower immune responses to diphtheria and pertussis antigens compared to the standard schedule 4

Clinical Implications and Considerations

• The waning immunity observed with DTaP vaccines may necessitate earlier booster vaccination and repeated boosting strategies to achieve necessary "herd effects" to control the spread of pertussis 2
• School-entry (ages 4-7) provides an ideal opportunity to implement DTaP booster vaccination to address the gap between waning immunity from infant/toddler vaccination and future adolescent vaccination 5
• Multiple studies support the findings of a progressive decrease in DTaP vaccine effectiveness and increased risk for pertussis over time after receipt of the fifth dose 1
• The safety profile of DTaP vaccines is well-established, with significantly fewer adverse events compared to whole-cell pertussis vaccines 1