From the Guidelines
A Tdap titer test is crucial for determining immunity to tetanus, diphtheria, and pertussis, and it is recommended to assess immunity status, especially in high-risk individuals, such as healthcare workers and pregnant women, to guide booster vaccination decisions. The test measures antibody levels in the blood, helping healthcare providers evaluate whether a person has adequate protection against these diseases. According to the most recent guidelines from the Advisory Committee on Immunization Practices (ACIP) 1, for tetanus and diphtheria, specific antibody levels (typically above 0.1 IU/mL) are considered protective, while pertussis immunity assessment is more complex and less standardized.
Key Points to Consider
- If titers are low, a Tdap booster is recommended, typically given as a single 0.5 mL intramuscular injection, to maintain protection against these serious diseases.
- Titer testing is useful because immunity from Tdap vaccination wanes over time - tetanus protection lasts about 10 years, while pertussis immunity may decline within 2-4 years, as supported by studies on the duration of immunity after Tdap vaccination 1.
- Understanding your immunity status through titer testing helps avoid unnecessary vaccinations and ensures protection against these diseases, particularly in high-risk individuals.
Recommendations for Tdap Booster
- Healthcare workers and pregnant women (recommended during each pregnancy between 27-36 weeks) should receive a Tdap booster to reduce the risk of transmitting pertussis to infants and to maintain protection against tetanus and diphtheria.
- The ACIP recommends that adults aged 19-64 years should receive a single dose of Tdap to replace tetanus and diphtheria toxoids vaccine (Td) for booster immunization against tetanus, diphtheria, and pertussis if they received their last dose of Td >10 years earlier and they have not previously received Tdap, as stated in the guidelines 1.
From the Research
Tdap Titer Significance
The Tdap (Tetanus, diphtheria, and pertussis) titer test is used to determine immunity against these diseases.
- The test measures the levels of antibodies against tetanus, diphtheria, and pertussis toxins in the blood.
- A positive titer result indicates that an individual has sufficient antibodies to protect against these diseases, while a negative result may indicate the need for vaccination or booster shots 2, 3.
Immunity Duration
Research suggests that vaccine-induced immunity against tetanus and diphtheria toxins can last for several years.
- A study found that antibody responses to tetanus declined with an estimated half-life of 14 years, while antibody responses to diphtheria were more long-lived and declined with an estimated half-life of 27 years 3.
- Mathematical models predict that 95% of the population will remain protected against tetanus and diphtheria for ≥30 years without requiring further booster vaccination 3.
Vaccine Safety and Efficacy
Tdap vaccines have been shown to be safe and effective in preventing pertussis, tetanus, and diphtheria.
- A study found that the Tdap vaccine was well-tolerated and effective in preventing pertussis in adolescents and adults aged 10-64 years 2.
- Another study found that maternal Tdap vaccination during pregnancy can inhibit pertussis-specific responses in infants, but the quality of antibodies was better in whole-cell pertussis (wP) vaccinated infants compared to acellular pertussis (aP) vaccinated infants 4.
- A safety review of Tdap vaccines in adults aged ≥65 years found no new safety concerns and confirmed the vaccine's safety profile 5.